Pin Slide Disc Brakes Service Manual 4th Edition
Contents
1. 9 Visually inspect anchor plate for damage or defects to mating surfaces and at anchor plate pad abutment slippers If no damage is found continue with Step 10 If damage is found remove anchor plate and replace with ANCHOR PLATE REPLACEMENT KIT see Anchor Plate Replacement Instructions 10 Remove brake pad abutment slippers using a blunt nose drift pin or screwdriver and light hammer Avoid marring anchor plate abutment surfaces 11 Remove the upper and lower anchor plate pins and pin boots from the anchor plate gt On some rear axle applications the upper anchor plate trailing pin cannot be removed without removal of the anchor plate as shown in Figure 32 Reference pages 37 and 38 steps 11 1 to 11 8 for repair instructions Anchor plate pins and anchor plate pin bores with heavy corrosion as shown in Figure 31 must be replaced Refer to the Anchor Plate Replacement Instructions section of this manual Figure 31 Example of Anchor Plate Pin with Heavy Corrosion Plate Trailing Pin That Cannot Be Removed Edition 4 September 2012 Bosch Chassis Systems Control Anchor Plate Repair 32 Anchor Plate Repair Instructions continued 12 Remove and inspect pin boots for wear cuts or damage as shown in Figure 33 If pin boots show any signs of wear cuts or damage replace as indicated Otherwise clean pin boots with isopropyl or denatured alcohol and dry with clean cloth or shop air and reuse gt Do not allow2. 53 Rotors en R oto rs continued Lining Transfer Lining transfer is a thin layer of lining material that has built up on to the rotor braking surface Initially the lining deposits will be spotty As transfer progresses the lining deposits will be covering more of the braking surface Lining transfer may accelerate lining wear Lining transfer is the result of extremely high operating temperatures which may be caused by continued hard stops or brake system imbalance The rotor can be resurfaced to remove the lining deposits and restore a proper braking surface The rotor thickness after resurfacing must not be below the minimum thickness dimension Bluing Rotors A rotor that shows the signs of bluing has been subjected to extremely high temperatures This condition may be caused by continued hard stops or brake system imbalance Heat Spotted Rotors This condition indicates that the rotor has been subjected to extremely high temperatures that have caused structural changes to occur in the rotor material This can cause the rotor to be more susceptible to cracking The rotor should be resurfaced to remove the hard raised areas If resurfacing will not remove the heat spots or if the resurfacing reduces the rotor thickness below the minimum thickness dimension the rotor must be replaced Edition 4 September 2012 Bosch Chassis Systems Control en Rotors 54 Roto rs continued Heat Checking Heat ch
3. REMOVE LOWER BOLT PISTON BOOTS BRAKE LINE Figure 18 Remove Caliper From Anchor Plate gt Use care to avoid damaging or dislodging the upper or lower guide pin boots Do not pull on leading or trailing pins This may dislodge guide pin boot from either the leading or trailing pin or anchor plate grooves 6 Move caliper assembly away from rotor 7 After the caliper has been removed from the anchor plate remove contamination dirt and debris from the exterior of caliper machined faces and around the caliper piston boots gt Inthe event the original disc brake pads are to be reused be sure to mark them in some manner i e left front inner left front outer right front inner etc so that they are reinstalled in the same location Do not mark on pad face Inboard and outboard brake pads may not be interchangeable The word FORWARD and a forward rotor rotation direction arrow may appear on each pad backing plate refer to the Disc Brake Pads section for complete details Bosch Chassis Systems Control Edition 4 September 2012 19 Caliper Assembly Rebuild en Remove Pistons A Warning gt Always wear eye protection gt Use just enough air pressure to ease piston from caliper bore gt Keep hands clear of piston face to avoid possible injury if piston pops from its bore gt Cover pistons with a shop rag to prevent brake fluid spray as piston clears bore 1 Drain all fluid from the ca
4. 10 127 cubic inches 19 052 cubic inches Bosch Chassis Systems Control Edition 4 September 2012 47 Troubleshooting Troubleshooting Note en gt For system troubleshooting reference Class 5 to 7 Truck and Bus Hydraulic Brake System Diagnostic Guide CONDITION CAUSE REMEDY NOISE AND CHATTER squealing clicking or scraping sound upon brake application BRAKES GRAB severe reaction to pedal pressure Edition 4 September 2012 1 Bent damaged or incorrect pads Worn out lining plates rubbing rotor Rotor polished linings glazed Foreign material imbedded in linings Excessive rotor thickness variations or lateral runout Brake pads improperly installed with shoe plate against rotor Incorrect pads Pad contamination such as grease or brake fluid on pads Loose caliper at anchor plate guide pins Excessive rotor lateral runout 1 Replace with correct pads Always replace in axle sets Resurface or replace rotor Replace pads in axle sets Remove polish glaze Replace pads in axle sets Check bearing adjustment Resurface or replace rotor Replace pads by axle set Resurface or replace rotor Replace with correct pads by axle sets Repair grease seal or caliper as required Replace pads in axle sets Tighten to specifications Check bearing adjustment Resurface or replace rotor
5. The jack may lower or slip and serious personal injury could result Always support vehicle with suitable floor stands Always wear eye protection When disconnecting the brake line from the caliper do not use clamps on the flexible brake hose to seal line Brake hose damage may occur Always wear a respirator when working around brakes or brake lining dust 1 Remove caliper assembly pads and tie bar as described in Anchor Plate Repair Instructions 2 Remove hub rotor and anchor plate according to vehicle manufacturer s service procedure 3 Remove splash shield and ABS sensor bracket from anchor plate as shown in Figure 43 Edition 4 September 2012 Bosch Chassis Systems Control en Anchor Plate Replacement 40 Anchor Plate Replacement Instructions continuea ANCHOR PLATE Zuo DRIVER SIDE FRONT ABS SENSOR BACKING PLATE BRACKET ASSEMBLY 2x73mm nA PE XN BRAKES TYPICAL oe BAK L Shee ji G Pat pr CHOR PEATE pit Sat HOE SPLASH SHIELD ae ABS SENSOR BRACKET ABS SENSOR BRACKET ANCHOR PLATE SPLASH SHIELD DRIVER SIDE FRONT BACK DRIVER SIDE REAR BACKING PLATE ING PLATE ASSEMBLY 2x66mm ASSEMBLY 2x73mm and 2x66mm BRAKES BRAKES TYPICAL TYPICAL Figure 43 Splash Shield and ABS Sensor Mounting Bracket Removal and Installation 4 Install solash shield and ABS sensor bracket onto replacement anchor plate Refer to Figure 43 When installing the splash shield and ABS sensor bracket on the
6. 2x66mm and ZTSE4418 for a 2x73mm on top of a piston and piston boot so the word BOOT or BOOTSIDE is on the underside of the tool toward the piston shown in Figure 23 Step 2 Be sure to match the correct tool for the pistons being installed 3 Using a C clamp or arbor press gently press the piston past the piston seal and partially into the bore shown in Figure 23 Step 3 Avoid cocking or binding piston during installation If the piston does not press into the bore smoothly the piston is cocked in the bore and will need to be repositioned to better align the piston with the caliper piston bore Continue pressing the piston and piston boot into bore until they are fully seated into caliper shown in Figure 23 Step 4 4 Make sure that the piston boot flange ring is fully seated into the top groove of piston bore in the caliper face 5 Repeat this procedure for the other piston 6 Reinspect the caliper assembly Pistons must be fully inserted into the caliper piston bores Piston boots must be fully seated in the piston boot groove and the boot grooves in the caliper face reference Figure 3 7 Install a new bleed screw in the upper top brake fluid port when the caliper is in the on vehicle position Torque to 8 15 lb ft 10 20 Nem POSITION PISTON SQUARE IN BORE INSTALLATION TOOL PRESS PISTON INTO BORE SEAT PISTON IN BORE Figure 23 Pressing Pistons into Caliper Bores Edition 4 September 2012 Bos
7. bolt FINGER tight securing the caliper to the anchor plate NOTE Torque Procedure for ZOPS Caliper Mounting Bolts INSERT FLAT gm gt For ZOPS bolt and pin use BLADE ast i a medium to large flat blade SCREWDRIVER i Aa screwdriver under the pin flange to keep it parallel to the caliper abutment during bolt tightening For ZOH T bolt and pin screwdriver is NOT required CAUTION Do not allow screwdriver to puncture boot 14 Torque caliper mounting bolt to specified value refer to Fastener Torque Chart 15 Install the brake hose retaining clip fastener and torque to vehicle manufacturer s specification Bosch Chassis Systems Control Edition 4 September 2012 17 Caliper Assembly Rebuild en Brake Pad Replacement Continuea 16 If any hydraulic lines were opened or removed bleed brake system per the vehicle manufacturers recommended procedure for additional information refer to Preparing Brake System for Use 17 Install wheel tire and rim on vehicle and torque wheel attachment nuts per vehicle manufacturer s specification Remove floor stands 18 Before starting engine depress brake pedal several times to reseat brake lining to the rotor Check the master cylinder reservoir and fill if necessary Consult vehicle service manual for proper brake fluid level 19 After brake service be sure to test brakes prior to returning vehicle into service to ensure a firm pedal Caliper Assembly Rebuild Instruction
8. cause separation of the braking section from the mounting flange After installing a new disc brake rotor check the brake system for proper braking balance to prevent subsequent cracking Bosch Chassis Systems Control Edition 4 September 2012 55 Rotors en R oto rs continued Grease Stained Rotors Grease stained brake rotors will show discolored spots on the braking surface with oil and or grease spattered on the brake assembly This condition can be caused by a faulty hub lubrication system To correct the problem the source of the grease and or oil must be repaired Remove the brake assembly and clean component Replace the linings if they are soaked with oil or grease Edition 4 September 2012 Bosch Chassis Systems Control en Rotors 56 Resurfacing Rotors Rotors are considered acceptable for continued use without resurfacing when 1 Lateral runout and thickness variation is within specification 2 Rotor braking surface area is smooth with even wear Light grooving or heat checking is acceptable 3 Brake pads are being replaced with the SAME lining material type 4 Rotor thickness is more than the minimum allowable thickness dimension Rotors can be resurfaced to provide a new smooth braking surface The rotors should be resurfaced when 1 Lateral runout or thickness variation exceed maximum specification 2 Rotor braking surfaces are worn unevenly have deep grooves are scored heat spotted heat
9. checked or have excessive lining transfer 3 Replacing brake pads with a different lining material type If the rotor thickness after resurfacing is less than the minimum thickness dimension the rotor must be replaced Be sure to use good sharp cutting tools and proper cutting feed and speed when resurfacing the rotor Avoid dull cutting tools and tool chatter After remachining the rotor braking surfaces must be clean and smooth with a surface finish of 40 120 microinch 1 016 3 048 micrometers Check rotor surface finish radially across both braking surfaces Check rotor thickness and thickness variation to ensure they are within specifications After installing hub and rotor on the vehicle wash rotor braking surfaces with high grade denatured alcohol to remove all traces of grease oil or other residue DO NOT use gasoline mineral spirits or oil Check rotor lateral runout to ensure it is within a specification Replacement Rotors Disc brake rotors are carefully engineered to meet the specific requirements of each brake system All replacement rotors must meet the quality and performance standard set by the vehicle manufacturer Replacing worn or damaged rotors with rotors of equal quality allows the braking system to operate efficiently which will result in maximum stopping performance longer service life between relining and overall lower brake maintenance costs Bosch Chassis Systems Control Edition 4 September 2012 Cor
10. commercially available brake cleaners to come into contact with piston seals piston boots or pin boots or they will be damaged gt Use only isopropyl or denatured alcohol to clean pin boots 13 Using isopropyl or denatured alcohol clean and wipe leading and trailing pins dry with clean shop cloth as shown in Figure 35 and inspect for damage or corrosion 14 Some leading and trailing pin polishing is expected during normal use and will appear as shiny areas as shown in Figure 35 Pins with polishing may be reused Leading and trailing pins with light corrosion as shown in Figure 34 may be cleaned with 220 grit sandpaper Clean pin with isopropyl or denatured alcohol and air dry With small acid brush lubricate leading and trailing pin Figure 36 and pin boot beads Figure 37 with Disc Brake leading and trailing Pin Boot Grease gt Use only Disc Brake leading and trailing Pin Boot Grease Other greases may cause the bushing or boot to swell grow and affect proper brake operation Refer to the Lubricating section of this manual for details Bosch Chassis Systems Control Edition 4 September 2012 33 Anchor Plate Repair en Anchor Plate Repair Instructions continued i i amp t 7 29 2003 1421 Figure 34 Leading Pin with Light Corrosion Figure 35 Clean Leading and Trailing Pins Figure 36 Lubricate Leading and Trailing Pins Figure 37 Lubricate Boot Bead 15 Cleaning and lubricating anchor plate bore
11. the lighter vehicle weight classes the HX 402 EE is recommended for flat to slightly rolling terrain and a mixture of urban and rural driving that does not contain excessive stop and go operational duty cycle that results in prolonged lining temperatures greater than 450 F Note HX 402 EE Material Because this lining material was developed specifically for light duty application it is very important to understand and follow the vehicle manufacturer s recommended application guidelines Improper vehicle application could result in unacceptable lining life gt Using HX 402 EE on vehicles with GVWR gross vehicle weight rating greater than 26 000 Ib could affect stopping distance Application Notice gt HX 402 EE is generally used for light duty applications where the HX 7A1 EE standard heavy duty lining may experience unbalanced or premature wear gt Heavy duty use of the HX 402 EE lining may result in accelerated wear Brake lining life is subject to vehicle duty and driver operating style and lining life will vary accordingly gt Do not use HX 402 EE on school buses exceeding 23 500 pounds GVWR with a 2x66mm rear brake Do not use HX 402 EE on school buses exceeding 25 999 pounds GVWR with a 2x73mm rear brake Edition 4 September 2012 Bosch Chassis Systems Control en General Description 10 Anchor Plate Leading and Trailing Pins and Caliper Mounting Bolt There are two caliper mounting bolts per brak
12. to Fastener Torque Chart or Figures 11 and 12 25 Torque trailing bolt to specified value refer to Fastener Torque Chart or Figures 11 and 12 26 Reinstall brake hose retaining clip bolt and torque to manufacturer s service manual specifications 27 Reinstall the tie bar 2x73mm brakes only Torque anchor plate tie bar bolts to 40 50 Ib ft 54 68 Nem 28 Reinstall anchor plate plug bolts 2x66mm brakes only Torque anchor plate plug bolts to 16 27 lb ft 22 37 Nem 29 Install wheel tire and rim on vehicle and torque wheel attachment nuts per vehicle manufacturer recommendation Remove floor stands 30 Before starting engine depress brake pedal several times to reseat the brake pads to the rotor Check for leaks in brake line connections Check the master cylinder reservoir and fill if necessary Consult vehicle manufacturer s service manual for proper brake fluid Edition 4 September 2012 Bosch Chassis Systems Control en Anchor Plate Repair 36 Anchor Plate Repair Instructions continued Note Torque Procedure for ZOPS Caliper Mounting Bolts gt For ZOPS bolt and pin use a medium to large flat blade screwdriver under the pin flange to keep it parallel to the caliper abutment during bolt tightening Insert Flat Blade Screwdriver For ZOH T bolt and pin screwdriver is NOT required CAUTION Do not allow screwdriver to puncture boot 31 After brake service be sure to test brakes prio
13. trailing pins pin boots and anchor plate pin bores Use 1 8 ounce of grease or one chamber of the Shell Albida MPS 1 Grease packet in the service kit Bosch part number 0204302291 to thoroughly lubricate each leading and trailing pin and anchor plate bore set Caliper Piston Bores Use only Disc Brake Corrosion Control Grease Batco or 1 2 of grease packet Bosch part number 0204262951 for each caliper piston bore Edition 4 September 2012 Bosch Chassis Systems Control en Fastener Torque 44 Brake Adjustment The Bosch pin slide caliper disc brakes are a self adjusting design and do not require periodic adjustments Wheel Bearing Adjustment Lateral runout or wobble in disc brake rotors can cause an increase in pedal travel due to piston knockback brake pedal pulsation during brake applications and increased piston seal wear since the pad is required to follow the rotor wobble Refer to vehicle manufacturer s service manual for proper wheel bearing adjustment Fastener Torque Chart ee ee ce ZOPS Caliper to Anchor Plate Heavy Hex Head Mounting i i Bolt For brakes manufactured prior to June 3 2002 70 80 95 108 ZOH T Caliper to Anchor Plate Flange Head Mounting Bolt For brakes manufactured after June 3 2002 93 107 126 145 The following are common for both ZOPS and ZOH T Caliper Designs Caliper Bleed Screw 5 15 10 20 Anchor Plate Tie Bar Mounting Bolt 2x73mm only 40 50 54 68 Anchor Plate Bolt Plug 2x66mm o
14. 12 49 Troubleshooting Tro u b es h O oti n 8g continued CONDITION CAUSE REMEDY ALL BRAKES DRAG but brakes operating correctly ONE BRAKE DRAGS Edition 4 September 2012 Binding brake pedal Soft or swollen rubber parts caused by incorrect or contaminated brake fluid Trapped pressure in brake lines caused by master cylinder booster or ABS not fully releasing Steering pump flow too high hydraulic booster only Loose or worn front wheel bearing Defective brake hose or hydraulic tube preventing return of brake fluid Sticking caliper piston Swollen caliper piston seal Sticking anchor plate leading or trailing pin s Trapped pressure in brake lines caused by master cylinder booster or ABS not fully releasing at one or more wheels Free up and lubricate Replace all rubber parts flush hydraulic system and fill with approved brake fluid Refer to vehicle manufacturer s service manual Check steering pump flow and repair or replace Adjust to specifications or replace Replace defective hose or tube as necessary Repair or replace caliper Repair or replace caliper Flush hydraulic system and fill with approved fluid Perform anchor plate repair procedure Refer to vehicle manufacturer s service manual Bosch Chassis Systems Control en Troubleshooting continues Tr
15. Bosch Chassis Systems Control Tro u b es h ooti n E continued Troubleshooting 48 CONDITION CAUSE REMEDY VEHICLE PULLS 1 TO ONE SIDE Incorrect pads Pad contamination such as grease or brake fluid on pads Loose caliper or anchor plate Caliper piston sticking Caliper guide pins sticking Excessive rotor lateral runout Vehicle loading Tire pressure or alignment PULSATING BRAKE PEDAL Worn or damaged front wheel bearings Excessive variation in rotor SPRINGY OR SPONGY PEDAL thickness Excessive rotor lateral runout Poor quality brake fluid low boiling point pedal has a soft springy or spongy feel when depressed Weak brake hoses that expand under pressure Air in hydraulic system Bosch Chassis Systems Control Replace with correct pads by axle sets Repair grease seal or caliper as required Replace pads in axle sets Tighten to specifications Rebuild caliper Replace caliper Repair or replace guide pins and boots Clean pin bores and lubricate Check bearing adjustment Resurface or replace rotor Redistribute weight Check tire pressure Align tires Replace wheel bearings Refinish or replace rotor Resurface or replace rotor Drain hydraulic system and fill with approved brake fluid Replace defective hoses Bleed hydraulic system Edition 4 September 20
16. Medium Heavy Truck Pin Slide Disc Brakes Service Manual i en Important Service Notes The information in this publication was current at the time of printing The information present ed in this publication is subject to change without notice or liability The information contained in this publication is intended for use by properly trained and equipped professional technicians and is NOT for the Do It Yourselfer gt Failure to follow all the safety and vehicle repair procedures either contained in this manual in the chassis and vehicle manufacturer s repair manuals or in accordance with other accepted methods can result in personal injury death or damage to components vehicles or personal property This manual can be viewed or downloaded at http www bosch us Edition 4 September 2012 Bosch Chassis Systems Control en ii Contents Introduction ZOPS and ZOH T Hydraulic Brakes ccccssscsssccssccscccsscccccccsccescceees 1 ZOH T Pin Slide Disc Brake COMPONENKG ccccccsccscccscccccccsccccccsccccccscccesccsccsccescces 2 General Description seosessessossosessesseosossssessessossosesseosessosesseosesssosssessessessssessossossssssees 3 Caliper Assembly Anchor Plate Leading and Trailing Pin and Caliper Mounting Bolt Disc Brake Pads Anchor Plate Assembly Introduction For Service Procedures eesssssscccccssseecccossseecososscccocsssseceosssesecsesssseesso 13 Bra
17. S gt CALIPER LEGS F Re ehh 2 f pS CALIPER EARS CALIPER LEGS Figure 17 Clean and Inspect Caliper Machined Surfaces Edition 4 September 2012 Bosch Chassis Systems Control en Pad Replacement 16 Brake Pad Replacement continuea 9 Inspect the rotor for scoring warping cracks or other damage or defects per rotor chassis or vehicle manufacturer s service manual If any damage or defects are found repair or replace per vehicle manufacturer s service procedure see Rotor section 10 Using a C clamp and piston insertion tool gently press both pistons into the bore until they are fully seated into caliper refer to Figure 23 Step 4 gt Verify master cylinder reservoir does not overflow when pushing pistons into housing bore 11 Position inner and outer pads over anchor plate slippers with lining material facing rotor for HX 7A1 EE refer to Figure 10 gt Be sure brake hose or line is not kinked and does not support the weight of the caliper 12 Align flat on upper top anchor plate pin head and rotate caliper closed to align with the flat on caliper upper top anchor plate pin boss Be careful when positioning caliper over the disc brake pads rotor and upper top anchor plate pin head to avoid tearing cutting or dislodging piston boots or anchor plate pin boots 13 When reusing caliper mounting bolts see Procedure for Reusing the Caliper Mounting Bolt Install upper top mounting
18. TE SHOE AND LINING STEEL BACKING PLATE Figure 9 Disc Brake Pad HX 7A1 EE shown Edition 4 September 2012 Bosch Chassis Systems Control en General Description 8 Disc Brake Pads continued gt The correct anchor plate leading and trailing pins caliper mounting bolts and bolt torque must be used Brake function could be affected and result in loss of brake function and loss of vehicle control which could cause personal injury death or vehicle component or property damage There are three 3 types of lining materials available for the Bosch ZOPS and ZOH T hydraulic disc brakes PFC 50 EF HX 7A1 EE and HX 402 EE gt The PFC 50 EF lining material was developed for heavy duty conditions and applications The pads are chamfered on each end of each pad The pads are interchangeable from inner to outer side of rotor however if pads are removed and then reinstalled the pads should be placed in same position from which the pads were removed This will result in best performance of pad lining life gt The HX 7A1 EE lining material was developed for heavy duty conditions and applications As a result some lining life compromise may occur if used in light duty applications The pads are chamfered and are marked with an arrow and the word FORWARD refer to Figure 10 to identify proper installation on the inner and outer side of the rotor Because these pads are chamfered they are NOT interchangeable between the inboar
19. a preventive maintenance program This can significantly reduce your per mile brake maintenance cost compared to reacting to brake problems as they occur The common rotor problems shown here can easily be seen by removing the tire and rim and inspecting the rotor surface The following are the most common problems experienced with rotors in the normal operation of the braking system If one or more of these problems exist the proper corrective action indicated should be taken immediately to ensure proper braking on demand Rotor Thickness Thickness Variation Check rotor thickness to make sure the thickness exceeds the minimum dimensions stamped or cast into the rotor Thickness variation should not exceed 0 002 when measured at several points around the rotor If the variation exceeds 0 002 and the rotor thickness exceeds the minimum dimension the rotor can be resurfaced The thickness of the resurfaced rotor must exceed the minimum thickness dimension f 16 82 R6052 Edition 4 September 2012 Bosch Chassis Systems Control en Rotors 52 R oto rs continued Lateral Runout Measure lateral runout using a dial indicator placed on the outer braking surface approximately 1 in from the rotor outside diameter Lateral runout should not exceed a total indicator reading of 0 020 during one full revolution on properly adjusted wheel bearings If lateral runout exceeds 0 020 total indicator reading check the mounting
20. anchor plate for 2x66mm front and all rear brakes the splash shield and ABS sensor bracket assembly are mounted on the inboard side of the anchor plate and the five bolts are installed from the inboard side Torque to 12 16 lb ft 17 21 Nem 5 On the 2x73mm front brakes the splash shield and ABS sensor bracket are mounted on the outboard side of the anchor plate and the five bolts are installed from the outboard side See Figure 43 Torque to 12 16 lb ft 17 21 Nem Bosch Chassis Systems Control Edition 4 September 2012 41 Anchor Plate Replacement en Anchor Plate Replacement Instructions continued gt Make sure guide pins are installed in the proper anchor plate location before continuing with anchor plate installations See Install Caliper section of this manual 6 Remove all traces of dirt grease oil etc from knuckle or axle flange 7 Exercise both pins to ensure afilm of grease is distributed over the pin It may take high effort to initially move and exercise one of the pins especially if the anchor has been unused for any length of time Position and secure anchor plate assembly to the front steering knuckle or to the rear axle flange Refer to vehicle manufacturer s service information for installation procedure and torque specs 8 Install brake hub and rotor according to vehicle manufacturer s service information 9 On 2x66mm pin slide disc brakes install four plug bolts into anchor plate face as
21. bolt ZOPS vs ZOH T on your vehicle torque the mounting bolt as follows Note Definition of Anchor Plate Leading and Trailing Position Imagine a point on exposed outboard surface of the rotor Now rotate the rotor as if the gt vehicle were moving in the forward direction The FIRST mounting pin that this point passes is the LEADING position The other is the TRAILING position See Figure 24 Definition of Anchor Plate LEADING and TRAILING Position Qa KTN 4 Vehicle Motion Driver Side Outboard View Vehicle Motion Passenger Side Outboard View Figure 24 Definition of Leading and Trailing Edition 4 September 2012 Bosch Chassis Systems Control en Caliper Assembly Rebuild 26 Install Caliper continued Caliper Mounting Bolt Torque Sequence ZOH T Bolt gt Torque leading bolt to 93 107 lb ft 126 145 Nem gt Torque trailing bolt to 93 107 Ib ft 126 145 Nem Flat Blade Screwdriver Torque the Leading bolt completely to 70 80 lb ft 95 108 Nem while holding the flat blade screwdriver under guide pin flange to keep it parallel to caliper abutment Torque the Trailing bolt completely to 70 80 lb ft 95 108 Nem using the same procedure as above 8 Connect the brake hose to the fluid inlet on the caliper and torque to vehicle manufacturer s specifications Do not allow the brake line hose to become pinched kinked or twisted 9 Install the
22. brake hose retaining clip fastener and torque to vehicle manufacturer s specification 10 Bleed brake system per the vehicle manufacturer s recommended procedure For additional information refer to Prepare Brake System For Use Bosch Chassis Systems Control Edition 4 September 2012 27 Caliper Assembly Rebuild en Install Caliper continued gt Make sure the bleed screw is properly torqued 11 Install wheel tire and wheel on vehicle and torque wheel attachment nuts per vehicle manufacturer s specification Remove floor stands 12 Before starting engine depress brake pedal several times to reseat the brake lining to rotor Check for leaks at the brake hose to caliper connection Check the master cylinder reservoir and fill if necessary Consult vehicle service manual for proper brake fluid level 13 After brake service be sure to test brakes prior to returning vehicle to service to ensure a firm pedal during application Edition 4 September 2012 Bosch Chassis Systems Control en Reusing Caliper Mounting Bolt 28 Procedure for Reusing Caliper Mounting Bolt Caliper mounting bolts should be replaced after the third use If unsure replace with new bolts In the sketches that follow a ZOH T bolt is shown but the same procedure applies to the ZOPS bolt 1 Visually inspect the removed bolts for any thread damage contamination or corrosion If damaged replace 2 Visually inspect the caliper mount
23. c pin slide disc brake is a two piston sliding caliper brake and is used at both front and rear wheel vehicle locations Each pin slide caliper disc brake wheel installation is made up of three major components as shown in Figure 2 gt Caliper assembly gt Anchor plate assembly gt Brake pads CALIPER ASSEMBLY ANCHOR PLATE ASSEMBLY Figure 2 Pin Slide Disc Brake Components Edition 4 September 2012 Bosch Chassis Systems Control en General Description 4 Caliper Assembly The disc brake caliper assembly is just one part of the entire vehicle brake system The caliper assembly contains two hydraulic piston bores The piston bores contain pistons piston seals and piston boots The caliper assembly attaches to and slides on sealed pins located in the anchor plate hence the term sliding or pin slide caliper assembly The front anchor plate is mounted on the front steering knuckle flange while the rear anchor plate mounts on the rear axle flange The caliper assembly comes in two sizes 2x 3mm and 2x66mm Either size may be on the front or rear vehicle location based on GVWR gross vehicle weight rating Refer to vehicle manufacturer s vehicle specifications for details The main components that make up the ZOH T pin slide caliper assembly are Caliper housing Housing bore grease Pistons Piston seals Piston boots Bleed screw Tube seats VVVVVVYV A cross section view of a disc brake caliper assembly as show
24. ch Chassis Systems Control en Caliper Assembly Rebuild 24 Install Caliper Make sure the leading and trailing pin flanges mounting bolts and mating caliper surfaces are clear of any grease or foreign matter Use clean shop cloth and isopropyl or denatured alcohol to remove foreign debris Install inner and outer pads over the slippers and replace them in the same location from which they were removed Verify the type of caliper mounting bolt and anchor plate pin installed in the anchor plate Refer to the Anchor Plate Leading and Trailing Pin and Caliper Mounting Bolt Section Figures 11 and 12 gt The correct caliper anchor plate leading and trailing pins and caliper mounting bolt torque must be used Brake function and loss of vehicle control may occur which could cause personal injury death or vehicle component or property damage You MUST use the correct bolt AND mounting torque with the correct pin hardware during service The ZOPS caliper mounting bolt prior to June 3 2002 is a M12x1 75x30 coarse thread with heavy hex head thread patch and yellow gold color INSTALLATION TORQUE IS 70 80 lb ft The ZOH T caliper mounting bolt after June 3 2002 is a M12x1 25x40 fine thread with a flange head with or without thread patch and dark gray in color Installation torque is 93 107 lb ft Refer to Anchor Plate Leading and Trailing Pin and Caliper Mounting Bolt section for details Because your vehicle may have ha
25. confirm that the seal is properly seated and that it is Figure 6 Piston Seal not twisted or rolled Piston seals must not come into contact with commercially available brake cleaners or they will be damaged Use only isopropyl or denatured alcohol during any brake servicing Piston Boot The piston boot as shown in Figure 7 is located at the face or opening of the caliper housing piston bore The piston boot is retained at its outside diameter in the housing and at its inside diameter by a groove in the piston The function of the piston boot is to provide a seal between the environment and the caliper bore The boot is produced via a molding operation of a rubber material around a stamped steel insert The insert located near the outside diameter of the piston boot provides piston boot retention within the caliper housing INSERT Figure 7 Piston Boot Note Piston Boot Never reuse old piston boots Visually inspect new piston boots for any cuts tears or damage Replace as required Verify that they are fully seated in caliper housing Piston boots must not come into contact with commercially available brake cleaners or they will be damaged Use only isopropyl or denatured alcohol during any brake service Bosch Chassis Systems Control Edition 4 September 2012 7 General Description en Bleed Screw and Tube Seat The function of the bleed screw as shown in Figure 8 is to provide a means to release entrapp
26. d with the rotor produces torque and the braking action of the vehicle The piston is molded and machined from a phenolic material and has a stainless steel cap Note Piston PISTON CAP The piston must be intact and free of pitting scoring or excessive wear If damage or defects are PISTON found replace as required Clean pistons with isopropyl or denatured alcohol before visual inspection Figure 5 Piston Assembly Edition 4 September 2012 Bosch Chassis Systems Control en General Description 6 Piston Seal The piston seal as shown in Figure 6 is a rectangular cross section seal made of a rubber compound The piston seal is placed in a groove that is machined into the caliper housing piston bore The piston seal s function is to provide a hydraulic seal between the piston and the caliper housing piston bore The piston seal also aids in retracting the piston i e pulls the piston back into the housing bore upon brake release This retraction allows clearance for the pads to be pushed back from the rotor Z Note Piston Seal a Never reuse old piston seals once the caliper assembly has been disassembled Dip new piston seals in clean hydraulic brake fluid type fluid as specified for your specific vehicle prior to installing seal into the housing seal groove WN Once the seal is in position in the housing piston seal ane Ze groove gently work around the groove with clean fingers ee oe to
27. d and outboard locations Recommended Application for PFC 50 EF or HX 7A1 EE Heavy Duty Lining Material gt PFC 50 EF or HX 7A1 EE is recommended for most applications This includes normal to heavier duty cycles with vehicle GVWRs typically greater than 26 000 Ib Typically these vehicles will operate in medium to heavy duty cycles with hilly to mountainous terrain stop and go driving quick stops from higher speeds etc This results in the linings being exposed to brake temperatures greater than 450 F for prolonged periods of use Arrow indicates rotor rotation for a Inner Pad vehicle moving in a forward direction As shown these pads would be used on the left side of the vehicle Note Disc Brake Pads gt Be sure the friction material side of the pad is against the ro BRAKE PADS tor Figure 10 HX 7A1 EE Brake Pads Outer Pad Bosch Chassis Systems Control Edition 4 September 2012 9 General Description en Disc Brake Pads continued gt HX 402 EE lining material was developed for use in light duty applications The pads are NOT chamfered and ARE interchangeable from the inner to outer side of the rotor on the same wheel Recommended Application for HX 402 EE Light Duty Lining Material gt HX 402 EE is recommended for light duty applications ONLY where the GVWR is typically 26 000 Ib or below and the brake linings will not see prolonged exposure to lining temperatures greater than 450 F In addition to
28. d prior brake servicing vehicles built prior to June 3 2002 may have been upgraded to the ZOH T leading and trailing pin and bolt design Refer to Pin Slide Disc Brake Components for details 4 Align flat on lower bottom anchor plate pin head with the flat on caliper housing lower 5 6 bottom anchor plate pin boss Be careful when positioning caliper over the disc brake pads rotor and lower bottom anchor plate pin head to avoid tearing cutting or dislodging piston boots or anchor plate pin boots When reusing caliper mounting bolts see Procedure for Reusing the Caliper Mounting Bolt Install lower bottom mounting bolt FINGER tight securing the caliper to the anchor plate Align the flat on the upper pin flange and then carefully rotate the caliper closed and install upper mounting bolt FINGER tight Bosch Chassis Systems Control Edition 4 September 2012 en 25 Caliper Assembly Rebuild Install Caliper continued Note Torque Procedure for ZOPS Caliper Mounting Bolts Insert Flat amp For ZOPS bolt and pin use Blade E 7 a medium to large flat blade Screwdriver L s Sg screwdriver under the pin flange to keep it parallel to the F Y s 24 pr a iin s haaa E i j f 5 caliper abutment during bolt bt wr S tightening _ d 4 7 For ZOH T bolt and pin screwdriver is NOT required CAUTION Do not allow screwdriver to puncture boot t 7 Depending on type of pin and
29. e assembly The bolts are used to secure the caliper assembly to the leading and trailing pins In turn the pins provide the sliding action relative to the anchor plate The anchor plate leading and trailing pins and caliper mounting bolts are common for both 2x66mm and 2x73mm caliper sizes ZOPS Pin and Bolt ZOH T Pin and Bolt Prior to June 3 2002 After June 3 2002 Leading and h Trailing Pin Bolt Leading Pin Heavy Hex Head Flange Head Coarse Thread M12x1 75x30 Fine Thread M12x1 25x40 Yellow in color Dark in color Nylon Patch May Have Adhesive Thread Patch Torque 70 80 lb ft 95 108 Nem Torque 93 107 lb ft 126 145 Nem Figure 11 ZOPS Caliper Mounting Bolt and Figure 12 ZOH T Caliper Mounting Bolt and Pins Pins The ZOH T anchor plate leading and trailing pins and caliper mounting bolts are NOT separately interchangeable or backward compatible with the original ZOPS caliper pins and mounting bolts due to the change in the bolt length and thread form from coarse thread to fine thread When changed out as a complete set the ZOH T caliper pins and mounting bolts are interchangeable and can be used in anchor plate and caliper housings produced prior to June 3 2002 The ZOH T leading and trailing pin designs are unique and MUST be installed in the correct anchor plate position Leading pin MUST be installed in the leading anchor plate location Trailing pin MUST be installed in the trailing anchor plate location R
30. ecking is the appearance of short thin radial interruptions of the braking surfaces of the rotor Heat checking is a normal phenomena of the disc brake function Heat checking is the result of the heating and cooling of the braking surface as the brakes are applied during operation of the vehicle Heat checks are not detrimental to the function or the performance of the braking system and no corrective action is required for this condition Heat checks will frequently wear away then reform as a result of the normal braking process However in some cases heat checks can progress over time into cracks in the braking surface depending on such factors as lining rotor wear rate friction material brake system balance and how hard the brakes are used Rotors with cracks extending beneath the pad rubbing surface should be replaced Cracked Rotors Braking surface cracks are radial cracks in the braking surface and rounding the edge of the rotor at the inside or outside diameter of the braking surface These cracks are usually caused by severe brake use or braking imbalance which shifts a greater share of the braking function to only a few brakes The brakes performing the greater share of the braking will always show the greater rotor wear and will sometimes crack Cracked rotors must be replaced If the rotor is not replaced the cracks will accelerate lining wear and can eventually progress into the barrel section of the rotor and
31. ed Truck ZOH T disc brake caliper assemblies were introduced into production on June 3 2002 The new caliper assembly has differences from its predecessor the ZOPS caliper assembly as follows gt Anchor plate leading and trailing pins The trailing pin has identification notches and a rubber bushing reference page 11 gt Caliper mounting bolts The bolt is longer dark in color has a flange head and fine threads and is tightened to a higher torque The bolt may be plain or have an adhesive patch The ZOH T anchor plate leading and trailing pins and caliper mounting bolts are NOT separately interchangeable or backward compatible with the original ZOPS anchor plate leading and trailing pins and caliper mounting bolts due to the change in the bolt length and thread form from coarse thread to fine thread When changed out as a complete set the ZOH T anchor plate leading and trailing pins and caliper mounting bolts are interchangeable and can be used in anchor plate and caliper housings produced prior to June 3 2002 The ZOH T leading and trailing pin designs are unique and MUST be installed in the correct anchor plate position Leading pin must be installed in the leading anchor plate location Trailing pin must be installed in the trailing anchor plate location Reference page 25 Figure 24 for leading and trailing definition Because your vehicle may have had prior brake servicing vehicles built prior to June 3 2002 may ha
32. ed air within the circuit of the brake system containing the caliper Purging the entrapped air within the brake system is commonly referred to as bleeding the brake system The function of the tube seat is to provide a seal between caliper housing and the bleed screw or hydraulic brake line tube fitting 7 16 INCH RENCH FLATS SHIPPING PLUG ey p TUBE SEAT LOCATIONS NIPPLE FOR BLEED HOSE ATTACHMENT Figure 8 Bleed Screw and Tube Seat Note Bleed Screw gt Inspect bleed screw for stripped threads or damaged wrench flats Replace as required Disc Brake Pads There are two pads per caliper assembly and they are referred to as the inner pad and outer pad The terms inner and outer pad are derived from their position relative to the caliper The inner pad is between the caliper piston and rotor The outer pad is between the rotor and caliper housing legs The pad is made of friction material and a steel backing plate The pad is also commonly referred to as the shoe and lining assembly Some pads have slots or chamfers machined areas as shown in Figure 9 which are used to abate noise Disc brake pads come in two sizes thicker friction material pads for the 2x73mm and thinner friction material pads for the 2x66mm calipers The steel backing plate is the same for both 2x 3mm and 2x66mm pads gt Always wear a respirator when working around brakes or brake lining dust CHAMFER CHAMFER FRICTION MATERIAL OPPOSI
33. eference page 25 Figure 24 for leading and trailing definition Because your vehicle may have had prior brake servicing vehicles built prior to June 3 2002 may have been upgraded to the ZOH T pin and bolt design Bosch Chassis Systems Control Edition 4 September 2012 11 General Description en Anchor Plate Assembly The components that make up both the ZOPS and ZOH T anchor plate assembly as shown in Figure 13 are Anchor plate Leading and trailing pins Pin boots Pin lubrication grease Abutment slippers Tie bar and tie bar attachment bolts 2x73mm only Anchor plate plug bolts 2x66mm only VVVVVVYV The anchor plate assembly includes lubricated floating leading and trailing pins sealed by rubber boots The anchor plate abutments are protected by stainless steel slippers A tie bar connects the anchor plate abutment arms and is used on the 2x73mm ZOPS and ZOH T pin slide disc brake installations only LEADING POSITION AFTER JUNE 3 2002 LEADING PIN AND BOOT ABUTMENT SLIPPER TRAILING PIN AND BOOT TRAILING POSITION AFTER JUNE 3 2002 TYPICAL LEFT FRONT SHOWN INBOARD VIEW NOTE ZOH T LEADING AND TRAILING PINS SHOWN REFER TO FIGURES 11 AND 12 FOR DETAILS Figure 13 Typical Anchor Plate Assembly Edition 4 September 2012 Bosch Chassis Systems Control en General Description 12 Anchor Plate Leading and Trailing Pin Pin Boot and Lubrication Grease The caliper is mounted to the anch
34. floor stands 2 Remove the brake hose retaining fastener This will allow easier pad removal Not required on all applications 3 Remove the upper top caliper mounting bolt securing the caliper to the upper anchor plate pin as shown in Figure 15 TYPICAL HOSE L RETAINER UPPER CALIPER CAUTION PINCH MOUNTING POINT TAKE CARE BOLT WHEN ROTATING CALIPER DO NOT ALLOW CALIPER TO BE SUPPORTED BY BRAKE LINE Figure 15 Rotating Caliper for Pad Replacement Edition 4 September 2012 Bosch Chassis Systems Control en Pad Replacement 14 Brake Pad Replacement continuea 4 Rotate the caliper down and support it with a suitable stand as shown in Figure 16 Do not allow the caliper to be supported by the brake line gt Keep grease and other foreign material away from pads rotor caliper assembly and external surface of the hub Handle parts carefully to avoid damage to the caliper rotor and brake lines Figure 16 Support Caliper Assembly with Stand 5 Remove inner and outer pads from anchor plate and inspect for wear or damage If lining thickness at the thinnest point is 3 16 inch 4 76 mm or less THE PADS MUST BE REPLACED In the event the original disc brake pads are to be reused be sure to mark them in some manner i e left front inner left front outer right front inner etc so they are reinstalled in the same location Do not mark on pad face When replacing brake pads
35. her foreign materials away from caliper assembly disc brake pads brake rotor and external surfaces of hub Handle parts carefully to avoid damage to caliper rotor disc brake pads and brake lines A jack must never be used alone to support a vehicle while under chassis service is being performed The jack may lower or slip and serious personal injury could result Always support vehicle with suitable floor stands Always wear eye protection When disconnecting the brake line from the caliper do not use clamps on the flexible brake hose to seal line Brake hose damage may occur Always wear a respirator when working around brakes or brake lining dust 1 Position vehicle on suitable floor stands and remove wheel tire and rim 2 Remove the brake hose retaining fastener This will allow easier caliper removal and installation not required on all applications 3 Remove lower bottom caliper mounting bolt securing the caliper to the anchor plate 4 Remove upper top caliper mounting bolt securing the caliper to the anchor plate Edition 4 September 2012 Bosch Chassis Systems Control en Anchor Plate Repair 30 Anchor Plate Repair Instructions continues 5 Move caliper assembly away from rotor and place it in a secure location on the vehicle suspension or place on suitable stand Secure the caliper assembly so that it does not fall gt Be sure brake hose or line is not kinked and does not support the we
36. ight of the caliper 6 Remove inboard and outboard disc brake pads from anchor plate pad abutment slippers and inspect pads refer to Disc Brake Pads section of this manual for details gt In the event the original disc brake pads are to be reused be sure to mark face them in some manner i e left front inner left front outer right front inner etc so they are reinstalled in the same location Do not mark on pad CLEAN MACHINED SURFACES gt CALIPER EARS gt CALIPER LEGS F peT 2 i SIH wh ta iw N 4 CALIPER EARS CALIPER LEGS Figure 29 Clean and Inspect Caliper Machined Surfaces 7 Check the external machined surfaces of caliper as shown in Figure 29 If any rust or contaminants are present use a hand held wire brush to clean the surfaces If any grease or oil is present use isopropyl or denatured alcohol on a clean shop cloth to remove it Check slipper mounting as shown in Figure 30 to be sure slippers are securely installed If damage or defects are found replace as required Bosch Chassis Systems Control Edition 4 September 2012 31 Anchor Plate Repair en Anchor Plate Repair Instructions continues SLIPPER MOUNTING Figure 30 Clean Anchor Plate Machined Surfaces 8 Visually inspect caliper for leakage damage or defects to piston boots or pistons If leakage or damage is found repair or replace as required refer to Caliper Assembly Rebuild Instructions for details
37. ing bolts for a white yellow residue or a blue green residue on ZOPS bolts resulting from a previously applied adhesive patch as shown in Figure 25 If no patch appears skip Step 3 and continue on to Step 4 3 Using a steel brush buff the adhesive residue from the bolt threads as shown in Figure 26 Buff only the area where the adhesive is present so the protective coating on the remainder of the threads is not removed Be sure to completely remove the existing adhesive so bare steel is showing where the adhesive was as shown in Figure 27 Figure 25 Used Caliper Mounting Bolt Figure 26 Use a Steel Brush to Buff with Adhesive Patch on the Threads Away the Existing Adhesive Residue jig tL rbleyaplcubl hI i Figure 27 Once the Adhesive is Removed a Clean Shiny Steel Surface Should Remain Bosch Chassis Systems Control Edition 4 September 2012 29 Anchor Plate Repair en Procedure for Reusing Caliper Mounting Bolt continues 4 Clean bolt with isopropyl or denatured alcohol Dry with low pressure shop air or clean shop cloth 5 Apply a patch of liquid Loctite 243 adhesive on bolt in the area of engaged threads indicated in Figure 28 Apply sufficient Loctite 243 adhesive to fill all engaged threads The adhesive develops usable strength within one hour eRe LI Figure 28 Liquid Loctite 243 Adhesive Applied to the Clean Threads for Reinstallation Anchor Plate Repair Instructions gt Keep grease and ot
38. it is recommended to replace all the disc brake pads at the same time This will maintain brake balance At a minimum change all pads on one axle at the same time Never change pads at one wheel end only Pads that exhibit excessive crumbling cracking corrosion or have less than 80 contact with the rotor must be replaced Anchor plate slippers are included in pad service kits and should be installed when replacing pads Bosch Chassis Systems Control Edition 4 September 2012 15 Pad Replacement en Brake Pad Replacement continuea gt When replacing pads use the SAME lining material type on both front and rear axles Using different lining materials can alter brake performance and lining wear gt Pads that have been contaminated with grease oil solvents or other foreign material must be replaced 6 Remove slippers Clean anchor plate abutments and install new slippers refer to Figure 41 Inspect pins and pin boots for wear or damage If any damage or defects are found repair or replace as required see Anchor Plate Repair Instructions Inspect caliper for fluid leakage and piston or piston boot damage If leakage damage or a defect is found repair or replace as required see Caliper Assembly Rebuild Instructions Check machined surfaces of caliper as shown in Figure 17 If any rust or corrosion is present carefully clean surfaces with hand held wire brush CLEAN MACHINED SURFACES gt CALIPER EAR
39. ke Pad Replacement e eeseseosesseseseoseseoseseosesessosessosessosessosessosessososessossosossssossssoseo 13 Caliper Assembly Rebuild Instructions seoseoseossossessoosesssossossessessesseoseessossessossoo 17 Procedure for Reusing Caliper Mounting Bolt cccccsscssssccssssccssssccssscccscscoescscess 28 Anchor Plate Repair Instructions seoseoseososeosessessossosessessessossosessessossosessessessosssses 29 Anchor Plate Replacement Instructions cccccsccsscssccscccssccsccscccscccecccsccsscceccceccees 39 Prepare Brake System for Use ssosssosssossosssosseossessesssesssosseessossseosesssossesssesssessesoses 42 EUG QUO WD eisereen eae r EE SEEE EA 43 Fastener Torque Chart esessesessesessesessesessosessosessosessosessosessosesessosessosessosessosessosessoses 44 Speca TOOLS soorpererrrr E oror EE AEA REE E ITE EEE 45 SpeciNCANONS ccccecccsccvecctensecsecsaceseccsasceteesecesseosvesnesodcdouceessscesessseesassoasbecsssceeccesosseeeeeneess 46 THOU ESO QUID E ao cases eco sis cide resorni rE ET E E 47 ROLTONG cccecscsecssntosesetssacsdasascnsesassssewncessocsseecsusssosseensossadosseossesscosstsssasasdoasassadeseessecsosnscasapenss 51 Bosch Chassis Systems Control Edition 4 September 2012 1 Introduction en Introduction ZOPS and ZOH T Hydraulic Brakes The Zero Offset Pin Slide ZOPS disc brake caliper assemblies were in production prior to June 3 2002 The Zero Offset Harmoniz
40. liper Dispose of brake fluid properly NO Place a spacer block approximately 1 3 4 to 2 inches thick between the caliper outer shoe legs and piston faces Cover pistons with a shop rag to contain brake fluid spray Refer to Figure 19 Make sure one caliper fluid port is sealed with a bleed screw and the other port IS open 3 Use an air blow gun as shown in Figure 19 to carefully apply low air pressure not to exceed 50 psi into the open caliper port to slowly push pistons out of caliper bores Pistons will push out against the spacer block 4 If only one piston pushes out of the caliper push that piston back into the bore against the seal and wedge a screwdriver between the outer shoe legs and spacer block Cover pistons with a shop rag to prevent fluid spray and carefully apply low air pressure not to exceed 50 psi into the open caliper port to slowly push out the other piston 5 Remove spacer block and then remove each piston from its piston bore and discard 6 Remove each piston boot from its boot groove in the caliper Remove piston seals from caliper bores Use a non metallic tool so as not to scratch the housing bore or seal groove Discard piston seals and boots CAUTION PINCH POINT KEEP HANDS CLEAR OF THIS AREA SHOP RAG NOT SHOWN FOR CLARITY a LOW PRESSURE H AIR INTO BRAKE LINE ORIFICE S SA SPACER BLOCK TO STOP PISTONS Figure 19 Removing Pistons Edition 4 September 2012 Bosch Chassis System
41. n in Figure 3 indicates the location of the components CALIPER HOUSING A og NO J PADS FIT INSIDE PISTON BOOT THE CALIPER IN PISTON THIS AREA PISTON SEAL IY TUBE SEAT AND BLEED SCREW INLET PORT LOCATION Figure 3 Caliper Assembly Bosch Chassis Systems Control Edition 4 September 2012 5 General Description en Caliper Assembly The caliper housing as shown in Figure 4 is the principle component of the caliper assembly It forms the supporting structure that withstands the applied hydraulic pressure It is produced as a casting and is then machined to final form The material of the caliper housing is ductile iron and has a protective coating to provide additional environmental protection The disc brake caliper housing straddles the rotor the inner pad and the outer pad Note Caliper Housing MACHINED YA SURFACES The machined surfaces of the caliper housing must be clean and free of dirt debris lubricants and foreign materials If damage or defects are found replace as required Figure 4 Caliper Housing Piston The piston as shown in Figure 5 is cylindrical in shape and is retained within the caliper housing piston bore The function of the piston is to react to the applied hydraulic brake fluid pressure by sliding out of the caliper housing piston bore It is this movement of the piston out of the caliper housing that results in pad contact with the rotor The contact of the pa
42. nly 16 27 22 3 ABS Sensor Bracket to Anchor Plate Mounting Bolts 12 16 17 21 Splash Shield to Anchor Plate Mounting Bolts 12 16 17 21 Bosch Chassis Systems Control Edition 4 September 2012 45 Special Tools en Special Tools Piston and Piston Boot Installation Tool Refer to Figure 46 and Figure 47 for Special Service Tools 0204102034 Disc Brake Caliper Piston and Piston Boot 2x66mm Disc Brake Caliper Installation Tool Same as ZTSE4417 0204102033 Disc Brake Caliper Piston and Piston Boot 2x73mm Disc Brake Caliper Same as Installation Tool ZTSE4418 Figure 47 2x73mm Piston and Pie uteeGs sooty PIRON ana piston Boot Insertion Tool Piston Boot Insertion Tool Edition 4 September 2012 Bosch Chassis Systems Control Specifications po To Piston Pin Slide Caliper 2x73mm REAR TwoPiston Pin Slide Caliper 2x66mm po Two Piston Pin Slide Caliper 2x73mm CALIPER MILLIMETERS nominal INCHES nominal Piston Bore Diameter 66 17 Piston Bore Diameter 73 20 ITEM 2X66mm CALIPER 2X73mm CALIPER Lining per pad Thickness new 0 49 inch 0 74 inch Thickness discard 0 187 inch 0 187 inch Rotor typical Outside diameter 15 0 inch 15 0 inch Thickness new 1 435 inch 1 435 inch Thickness discard 1 320 inch 1 320 inch Surface finish 40 120 micro inches 40 120 micro inches 40 100 micro inches pre 40 100 micro inches pre ferred ferred Reservoir fluid replacement per caliper typical
43. of cleaning fluid Make sure hands are free of dirt and oil Bosch Chassis Systems Control Edition 4 September 2012 21 Caliper Assembly Rebuild en Assemble Caliper 1 Dip NEW piston seals in clean hydraulic brake fluid vehicle specific fluid type and install in the piston seal groove of caliper piston bores as shown in Figure 21 With the piston seal positioned in the groove gently work around groove with clean fingers until seal is properly seated into groove Be sure seal is not twisted or rolled Using a small acid brush apply a film of Disc Brake Corrosion Control Grease from the packet contained in the service kit to the caliper bore seal land area between the piston boot and seal grooves shown in Figure 21 Use half of the grease packet for each piston bore Apply the grease to the areas shown in Figure 21 around the entire circumference of the caliper seal land area APPLY DISC BRAKE CORROSION LY ARA CONTROL GREASE IN THESE AREAS CALIPER BE SURE SEAL IS SEATED SQUARELY IN GROOVE SEAL MUST NOT BE TWISTED SEAL LAND Figure 21 Piston Seal Installation A Warning gt Use only Disc Brake Corrosion Control Grease on seal land Other greases may cause seals or boots to swell grow and affect proper brake operation Refer to the Lubrication section of this manual for details Edition 4 September 2012 Bosch Chassis Systems Control en Caliper Assembly Rebuild 22 Install Piston Boot
44. or plate leading and trailing pins The leading and trailing pins are inserted into the anchor plate pin bores which are lubricated with grease as shown in Figure 14 The function of the leading and trailing guide pins is to position the caliper assembly relative to the rotor and provide the means for the caliper assembly to slide either inboard or outboard to compensate for pad wear and provide a means for pad clearance to the rotor during non braking situations The function of the pin boots is to seal the pins from the environment LEADING PIN PIN BOOT r E P 5 5 pe A a ia pe 5 ra ANCHOR PLATE LUBRICATION GREASE ZOH T LEADING PIN SHOWN The ZOH T anchor plate leading and trailing pins and caliper mounting bolts are NOT separately interchangeable or backward compatible with the original ZOPS caliper pins and mounting bolts due to the change in the bolt length and thread form from coarse thread to fine thread When changed out as a complete set the ZOH T caliper pins and mounting bolts are interchangeable and can be used in anchor plate and caliper housings produced prior to June 3 2002 The ZOH T leading and trailing pin designs are unique and MUST be installed in the correct anchor plate position Leading pin MUST be installed in the leading anchor plate location Trailing pin MUST be installed in the trailing anchor plate location Reference page 25 Figure 24 for leading and trailing definition Because
45. oreign matter Use a clean shop cloth and isopropyl or denatured alcohol to remove foreign debris 19 Clean anchor plate abutments with wire brush and reinstall slippers Figure 41 SLIPPER Figure 41 Anchor Plate Pad Abutment Slipper Installation Bosch Chassis Systems Control Edition 4 September 2012 35 Anchor Plate Repair en Anchor Plate Repair Instructions continued 20 Position inner and outer pads over anchor plate slippers with lining material facing rotor For HX 7A1 EE refer to Figure 10 21 Be sure to align flat on lower bottom anchor plate pin head with the flat on caliper lower bottom anchor plate pin boss Be careful when positioning caliper over the disc brake pads rotor and lower bottom anchor plate pin head to avoid tearing cutting or dislodging piston boots or pin boots 22 Install lower bottom mounting bolt FINGER tight securing the caliper to the anchor plate 23 Align the flat on the upper pin flange then carefully rotate the caliper closed and install upper mounting bolt FINGER tight Do not allow the brake line hose to become pinched or kinked When tightening the caliper mounting bolts refer to Definition of Anchor Plate Leading and Trailing Position Figure 24 Note Reusing Caliper Mounting Bolts gt When reusing caliper mounting bolts see Procedure for Reusing the Caliper Mounting Bolt before proceeding with Step 24 24 Torque leading bolt first to specified value refer
46. oubleshooting 50 CONDITION CAUSE REMEDY LOW PEDAL pedal may go to floor under steady pressure LOW PEDAL pedal may go to floor on first application and is OK on subsequent applications HARD PEDAL 1 Leak in hydraulic system Air in hydraulic system Poor quality brake fluid low boiling point Low brake fluid level Weak brake hoses that expand under pressure Excessive pad and piston knockback caused by loose wheel bearings or rotor runout Excessive rotor runout Air in brake system Faulty ABS Note Check master cylinder calipers tubes and hoses for leakage Repair or replace faulty parts Bleed hydraulic system Drain hydraulic system and fill with approved brake fluid Fill master cylinder and bleed hydraulic system Replace defective hoses Adjust or replace wheel bearings as necessary Repair replace rotor Bleed brakes Refer to vehicle manufacturer s service manual for ABS service procedure gt For system troubleshooting reference Class 5 to 7 Truck and Bus Hydraulic Brake System Diagnostic Guide Bosch Chassis Systems Control Edition 4 September 2012 51 Rotors en Rotors Always refer to rotor or vehicle manufacturer s service manual for specific details The following is offered as a general guide Inspection A regular inspection of the braking system should be included as a part of
47. r to returning vehicle into service to ensure a firm pedal during brake application 32 Refer to Prepare Brake System for Use for additional information Bosch Chassis Systems Control Edition 4 September 2012 37 Anchor Plate Repair en Anchor Plate Repair Instructions continued Rear Axle Upper Top Anchor Plate Trailing Pin Only 11 1 11 2 11 3 11 4 11 5 11 6 11 7 11 8 Note gt On some rear axle applications the upper caliper anchor plate trailing pin cannot be removed without removal of the anchor plate as shown in Figure 32 Pull the trailing pin out of the anchor plate bore as far as possible Use a clean cloth dampened with isopropyl or denatured alcohol to clean trailing pin and pin boot Air dry with low pressure shop air gt DO NOT use liquid alcohol directly on anchor plate pins or in anchor plate bore It may collect in anchor plate bore and degrade leading and trailing pin lubricating grease Inspect trailing pin and pin boot If pin boots show any signs of wear cuts or damage replace as indicated Otherwise clean with isopropyl or denatured alcohol dry with a clean cloth or shop air lubricate with Disc Brake Leading and Trailing Pin Boot Grease and reuse Cut off damaged boot Lubricate trailing pin with Disc Brake Leading and Trailing Pin Boot Grease Carefully install new boot over pin flange and seat boot into groove as shown in Figure 42 Verify that the boot
48. respondence concerning this manual should be addressed to Robert Bosch LLC Attn Medium Truck Brake Engineering 3737 Red Arrow Highway St Joseph Michigan 49085 Fax 269 428 6704 Printed in the United States of America Copyright 2012 Robert Bosch LLC
49. s 1 Position new piston boot on top of new piston shown in Figure 22 Step 1 with boot flange properly oriented The small dimples on the piston boot flange must be toward the open end of the piston Carefully pull piston boot down over the top of the piston shown in Figure 22 Step 2 3 and 4 until inner bead of boot is seated in the piston boot groove shown in Figure 22 Step 5 2 Return the boot to the collapsed or folded position Make sure the boot is fully seated in the piston boot groove by grasping the piston boot flange and rotating piston back and forth shown in Figure 22 Step 6 gt Clean hydraulic brake fluid vehicle specific fluid type or disc brake corrosion control grease may be used on piston boot inner bead and outer ring to ease assembly Do not use any other lubrication INNER BEAD INNER BEAD PISTON FACE PISTON BOOT GROOVE INNER BEAD INNER BEAD PISTON BOOT INNER BEAD SEATED IN GROOVE Figure 22 Installing Piston Boot to Piston Bosch Chassis Systems Control Edition 4 September 2012 23 Caliper Assembly Rebuild en Install Pistons 1 Apply hydraulic brake fluid vehicle specific fluid type to outside of piston and carefully position piston with piston boot into caliper bore shown in Figure 23 Step 1 2 Position the piston and boot installation tool 0204102034 for a 2x66mm brake or 0204102033 for a 2x73mm brake optional piston and boot installation tools ZTSE4417 for a
50. s Remove Caliper gt Keep grease and other foreign materials away from caliper assembly disc brake pads brake rotor and external surfaces of hub Handle parts carefully to avoid damage to caliper rotor disc brake pads and brake lines A jack must never be used alone to support a vehicle while under chassis service is being performed The jack may lower or slip and serious personal injury could result Always support vehicle with suitable floor stands Always wear eye protection When disconnecting the brake line from the caliper do not use clamps on the flexible brake hose to seal line Brake hose damage may occur Always wear a respirator when working around brakes or brake lining dust 1 Position vehicle on suitable floor stands and remove wheel tire and rim 2 Remove the brake hose retaining fastener This will allow easier caliper removal and installation required if caliper is removed from vehicle 3 Disconnect brake fluid line from caliper and cap line to prevent brake fluid leakage or contamination in the brake line refer to Figure 18 4 Remove upper top caliper mounting bolt securing the caliper to the upper anchor plate pin 5 Remove lower bottom caliper mounting bolt securing the caliper to the lower anchor plate pin Edition 4 September 2012 Bosch Chassis Systems Control en Caliper Assembly Rebuild 18 Remove Caliper continues REMOVE UPPER BOLT CLEAN MACHINED FACES PISTONS
51. s Using a round wire 5 8 inch diameter brush Figure 38 and isopropyl or denatured alcohol wire brush both upper and lower anchor plate pin bores Clean out any remaining loose residue with a clean shop cloth or swab Carefully air dry pin bores With small acid brush lubricate Figure 39 anchor plate bore with Disc Brake Leading and Trailing Pin Boot Grease Figure 38 Wire Brush Anchor Plate Figure 39 Lubricate Anchor Plate Bore Bore 16 To aid in leading and trailing pin installation it may be necessary to loosen the anchor plate tie bar bolts that are opposite the caliper leading and trailing pins on 2x73mm caliper assemblies or anchor plate plug bolts on 2x66mm caliper assemblies Be sure bolts are properly torqued per manufacturer s recommendation after pin installation Edition 4 September 2012 Bosch Chassis Systems Control en Anchor Plate Repair 34 Anchor Plate Repair Instructions continued 17 Assemble pin boots onto pins and install leading and trailing pin into the appropriate anchor plate bore Align the leading and trailing pin flange flats Figure 40a and 40b so that they are parallel to facilitate caliper installation Clean pin flange face with a clean cloth and denatured or isopropyl alcohol Air dry Figure 40a Install and Align Lead Pin Figure 40b Install and Align Trail Pin 18 Make sure that the leading and trailing pin heads mounting bolts and mating caliper surfaces are clean of any grease or f
52. s Control en Caliper Assembly Rebuild 20 Clean and Inspect Caliper Components 1 Inspect caliper for damage to piston bores and boot grooves If damage is found replace caliper SEAL GROOVES MUST BE FREE OF DIRT AND CORROSION CLEAN BOOT GROOVES gt CLEAN ALL MACHINED SURFACES BORES MUST BE FREE OF CORROSION AND PITTING Figure 20 Clean and Inspect Caliper Machined Surfaces 2 Check external machined surfaces of the caliper as shown in Figure 20 If any rust or corrosion is present at these locations carefully clean the surfaces with a hand held wire or brass brush gt Do not allow commercially available brake cleaners to come into contact with piston seals boots or pistons 3 Clean caliper caliper piston bores and fluid ports with isopropyl alcohol or denatured alcohol ONLY Use low pressure compressed air to clean out and dry grooves and passages Wipe out the bores with a clean dry cloth Use 320 to 400 grit emery cloth wire or brass brush as indicated to clean piston bores of debris and any light corrosion if present If corrosion is heavy in the bore and is not readily removed with a wire brush then replace caliper 4 Inspect caliper bores and seal lands reference Figure 21 to make sure they are clean and free of debris Repeat the cleaning process as necessary When using compressed air use air lines that are completely free of oil and moisture All brake parts must be clean and completely dry
53. s been removed from the brake system may be contaminated Contaminated brake fluid can cause damage to components loss of braking serious personal injury and property damage PROPERLY DISCARD ALL USED BRAKE FLUID gt Use only the type of brake fluid specified by vehicle equipment manufacturer gt The wrong brake fluid may damage the rubber components of the caliper assembly and can cause loss of braking serious personal injury and property damage gt Do not mix different types of brake fluid Bosch Chassis Systems Control Edition 4 September 2012 43 Lubrication en Brake Bleeding continued Note gt Use only vehicle specific brake fluid type with Bosch hydraulic pin slide disc brakes 1 Check the master cylinder reservoir and fill if necessary with brake fluid type fluid as specified for your specific vehicle 2 Bleed the entire brake system per vehicle manufacturer s service instructions 3 Bleed the caliper assemblies in the following order gt Right rear gt Left rear gt Right front gt Left front 4 Tighten bleed screw to 8 15 lb ft 10 20 Nem Lubrication gt Use only specified lubricants Other greases may cause seals and boots to swell grow and affect proper brake operation Anchor Plate Leading and Trailing Pins and Anchor Plate Pin Bores Use only Disc Brake Leading and Trailing Pin Boot Grease Shell Albida MPS 1 Grease as required when servicing the leading and
54. shown in Figure 44 Tighten to 16 27 lb ft 22 37 Nem 10 On 2x73mm pin slide disc brakes install the anchor plate tie bar and four tie bar bolts to the anchor plate face as shown in Figure 44 Torque bolts to 40 50 lb ft 54 68 Nem 7E TIE BAR 2x73mm ONL B PLUGS 2x66mm ONLY Figure 44 Installation of Tie Bar on 2x73mm or Anchor Plate plugs on 2x66 mm 11 Verify anchor plate abutment slippers are installed on the anchor plate reference Figure 45 Edition 4 September 2012 Bosch Chassis Systems Control Prepare Brake System 42 Anchor Plate Replacement Instructions continued SLIPPER Figure 45 Anchor Plate Pad Abutment Slipper Installation 12 Install caliper assembly to anchor plate according to the procedure described in the Anchor Plate Repair Instructions begin with step 20 page 35 Prepare Brake System for Use Brake Bleeding Note gt Refer to vehicle manufacturer s service manual for ABS bleeding instructions Warning gt Failure to bleed the hydraulic brake system whenever any hydraulic system component has been serviced or disconnected will allow air to enter into and remain in the brake system Entrapped air in the brake system will cause degraded brake system performance increased stopping distance and can result in property damage and serious personal injury gt Do not reuse brake fluid Brake fluid removed from the brake system must be discarded Brake fluid that ha
55. surfaces between the rotor and the wheel or hub fastener torques and wheel bearing adjustment Radial Runout Using a dial indicator check the radial runout as measured at the outside diameter of the braking surface The radial runout should not exceed 0 035 total indicator reading If the radial runout of the rotor exceeds 0 035 replace the rotor Clogged or Restricted Vent Holes Vehicles operating in severe duty environments may experience clogged or restricted vent holes due to the accumulation of mud gravel or other debris Such restrictions must be removed to provide even cooling of the rotor during normal operation Worn Rotors If the thickness of the rotors is at or below the minimum thickness dimension the rotor must be replaced If there is a sufficient thickness remaining on the rotor it may be resurfaced as long as the resulting thickness does not fall below the minimum thickness dimension Check the rotor to make sure that the wear is approximately equal on both braking surfaces If one surface is worn more than the other inspect the brake system for proper operation Scored Rotors A scored rotor has a rough grooved appearance on the braking surface If the scoring exceeds 015 and the rotor thickness exceeds the minimum dimension the rotor can be resurfaced The thickness of the resurfaced rotor must exceed the minimum thickness dimension Bosch Chassis Systems Control Edition 4 September 2012
56. ve been upgraded to the ZOH T pin and bolt design gt The correct anchor plate leading and trailing pins and caliper mounting bolts and bolt torque must be used Brake function could be affected and result in loss of brake function and loss of vehicle control which could cause personal injury death or vehicle component or property damage For additional details refer to the Anchor Plate Leading and Trailing Pins and Caliper Mounting Bolt section of this manual Edition 4 September 2012 Bosch Chassis Systems Control en ZOH T Components 2 Pin Slide Disc Brake Components Typical Exploded View of a ZOH T 2x73mm Left Front Brake Assembly CALIPER MOUNTING BOLT BLEED SCREW LEADING BRAKE CALIPER PIN LINE PORT 1 Fa j AL i T w E tes h F as J an J L A i SEAL QO ee osion TRAILING PIN BUSHING PIN vas BOOT SLIPPER ANCHOR ABS SENSOR BRACKET amp BOLTS PLATE PLUG ia TIE BAR NODULAR CAST IRON SPLASH 2X73mm ONLY STEEL SHIELD ELASTOMER PHENOLIC TIE BAR BOLT FRICTION MATERIAL 2X73mm ONLY Figure 1 Pin Slide Disc Brake Components Bosch Chassis Systems Control Edition 4 September 2012 3 General Description en General Description This section provides basic information about the components that comprise a hydraulic disc brake and their intended function Service information is contained later in this manual The Bosch hydrauli
57. was not torn during installation Push trailing pin into anchor plate bore and seat boot onto anchor plate boot groove Edition 4 September 2012 Bosch Chassis Systems Control en Anchor Plate Repair 38 Anchor Plate Repair Instructions continued Rear Axle Upper Top Anchor Plate Trailing Pin Only continuea Replacement Procedure for Damaged Pin Boot gt DO NOT cut grind or modify in any way the anchor plate leading and trailing pins or vehicle components when attempting anchor plate leading and trailing pin removal or installation Improper brake operation may occur if altered in any way Return to step 12 page 32 Anchor Plate Repair Instructions FPA ANCHOR PLATE BOOT GROOVE PIN BOOT GROOVE Figure 42 Installing Pin Boot over Pin Flange gt Do not allow commercially available brake cleaners to come into contact with piston seals piston boots or pin boots gt Use only isopropyl or denatured alcohol to clean leading and trailing pin boots Bosch Chassis Systems Control Edition 4 September 2012 39 Anchor Plate Replacement Anchor Plate Replacement Instructions gt Keep grease and other foreign materials away from caliper assembly disc brake pads brake rotor and external surfaces of hub Handle parts carefully to avoid damage to caliper rotor disc brake pads and brake lines A jack must never be used alone to support a vehicle while under chassis service is being performed
58. your vehicle may have had prior brake servicing vehicles built prior to June 3 2002 may have been upgraded to the ZOH T pin and bolt design gt The correct anchor plate leading and trailing pins caliper mounting bolts and bolt torque must be used Brake function could be affected and result in loss of brake function and loss of vehicle control which could cause personal injury death or vehicle component or property damage Bosch Chassis Systems Control Edition 4 September 2012 13 Introduction for Service Introduction For Service Procedures The sections that follow provide the recommended service procedures to be used on the Bosch Hydraulic Disc Brake Assembly All procedures are applicable for both ZOPS and ZOH T designs except as noted gt Failure to follow all the safety and vehicle repair procedures either contained in this manual in the chassis and vehicle manufacturer s repair manuals or in accordance with other accepted methods can result in personal injury death or damage to components vehicles or personal property Brake Pad Replacement 1 Position vehicle on suitable floor stands and remove wheel tire and rim gt Always wear a respirator when working on brakes or around brake lining dust gt A jack must never be used alone to support a vehicle while any service is being performed The jack may lower or slip and serious personal injury could result Always support vehicle with suitable
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