Opel GT Cooling System - Opel Motorsports Club
Contents
1. 190 degrees Or in other words almost always to the left of the center mark Stock GT s run best at about 185 degrees 176F 194F 212F Notes An effective cooling system is particularly required on the 1973 model year GT which had a 12 bolt cylinder head design that was prone to internal cracking between the 2 and 3 exhaust valve seats when it overheated When major service is performed also back flush the cooling system to remove internal rust Installing the Prestone brand flush and fill kit plastic tee fitting hardware makes back flushing the heater core much easier Always quickly clean up coolant leaks Fluid puddles attract animals and when ingested causes severe kidney damage amp death Recycle anti freeze in an environmentally safe manner Although there is an engine block drain plug which has a square head located on the passenger side rear of the engine it usually rusts too solid to safely try to remove the head usually just twists off Air Conditioning on a GT significantly affects fan pulley spacing radiator hose routing and the condenser mounting greatly affects radiator access Additional information on the ARA air conditioning system in the Opel GT ARA s auto trans interior A C console is shown at right is in the May 1995 OMC Blitz the GM A C system is well covered in the 1973 Opel factory service manual An index of prior OMC Blitz articles on the cooling system including the heate2. at the rem Wyo g lower middle of the pump shaft then it s time to change the water pump C YOA z a a a fi cae S Ea ty xa Replacement On the road following a sudden failure changing a water pump ee S N can be a challenge The radiator shroud if equipped with one needs to be unscrewed 7 av bl and unless you have nimble hands and an offset 13mm wrench to work within about 1 of clearance between the fan and the radiator fins to loosen the 4 fan bolts you also have to pull the radiator first When installing all surfaces need to be clean amp dry for gasket sealer Permatex high tack works well immediately as does RTV 1f you can wait 24 hours to take hold The 3 longer 11mm head bolts attach on the passenger side of the pump and the 3 shorter 11mm head bolts attach on the driver s side of the pump Start the bottom short 11mm bolt first as it s the hardest to align it s behind a lip of the k upper crankshaft pulley Torque all 11mm head bolts to 11 ft lbs F Go i Line up and bolt the 4 13mm head fan bolts length about 7 8 overal through holes in the pulley to attach to the pump It s a good idea to buy and keep a new water pump on hand at all times to avoid delivery delays when you really need it When a choice is available Closed round impeller style pumps may produce more flow than open star shaped styles Aluminum pumps are preferred over iron pumps as they do not prom
3. Because the thermostat housing is aluminum but is bolted to a cast iron cylinder head the attaching bolts frequently seize due to an mixed metal electrolysis reaction This means great caution should be taken when unbolting the 13mm bolts it s best to use a slow back and forth motion until the bolt is free to avoid breakage Assembly Prior to installation eliminate heat warpage by flattening the mounting surface facing the cylinder head of the aluminum housing using either a straight aluminum file in a vise or do figure eight motions on a piece of fine sandpaper on a flat cement garage floor The thermostat mounts in the recessed hole with the spring facing down and the pointed side facing up then the universal type gasket is placed over its edges Another good idea is to clean all the rust and gunk from the bolt threads and coat the bolt threads with anttseize liquid for additional protection when assembling Temperature Gauge Sender Units There was an early style 1968 69 temperature gauge sensor that had a 17mm wide fitting with a 14mm threaded hole but more common for the GT is the 13mm wide fitting with a black color insulator and a 10mm threaded hole Do not install the 13mm size sender with the white insulator that s the Manta s non rallye model sender The sender is connected to the blue white striped wire to the dash Some thermostat housings for aftermarket side draft car
4. Tuning the 1 9 Liter Opel Part II Opel GT Cooling System As the next section to OMC s June 2006 guide to tuning the 1 9 liter Opel what follows is an overview on the Opel cooling system focusing exclusively on the Opel GT The same principles generally apply to 1 9 liter engine Opel Mantas Asconas and Kadettes although these larger vehicles generally feature more effective stock cooling systems which do not suffer as much from under hood space restriction as in the stock GT The main variation on the 1 9 was the 1975 style used on original fueFinjection Opels which had a 6 blade white colored plastic fan and a fan clutch which quickly wore out the attached 1975 only water pumps due to the extra weight on their internal bearings and a different thermostat amp housing Maintenance of the Cooling System of the 1 9 Liter Opel GT is an ongoing process In general when you first acquire an Opel it s a good idea to flush all the coolant then to install all new common use components It s easier to just do this once than to drain the coolant over and over to perform repairs This means Fan Belt there are 2 sizes check lower alternator bracket early cast iron or late aluminum Radiator Hoses best to use pre formed hoses particularly on the lower hose than universal types and always replace hoses when they are cracked ballooned in a section or not firm mushy to the touch Heater Hoses sh
5. an rusted out original clamps The hose to the heater valve should be measured about 7 inches including an inch over the end of the metal tube to the heater core and cut so that the control cable to the lever on the heater valve will fully open and close the lever moves towards front of the car to open the heater valve Consider installing a plastic tee fitting from Prestone s Flush amp Fill Kit to connect a garden hose to back flush the heater core to use water pressure to dislodge internal rust and debris Heater Valve All but early 1968 69 GT s have this valve under the hood Remove carefully Press down and pull out the cable retainer clip make sure not to break the retainer tab then remove from the attached hoses and work lever carefully over the cable end the bent portion snaps easily In a sink use running warm water and light tapping to remove dirt and rust from the inside of the valve Use a SOS type scouring pad to clean off the exterior plunger rod Spray WD40 inside and out and test that valve moves easily Then verify motion of the inner cable by sliding the lower control lever on the dashboard if it doesn t move the brittle rear mounting bracket behind the dash has probably broken off You can adjust the heater valve manually or add a quick fix by installing a manual choke cable under the dash but eventually you should replace the original plastic heater control on the dash with a metal reproduc
6. buretors and the ARA air condition system added a 1 spacer to raise the cap piece Styles The early 1968 1972 thermostat housings had 3 attaching bolts and later 1973 thermostat housings had 2 bolts according to a 1973 Opel technical service bulletin Both styles of gaskets are interchangeable and work well and Silicone RTV sealer works great here if you can wait about 24 hours for it to dry If using Silicone RTV snug bolts into position but don t fully tighten until sealer has had 24 hours to dry www opelclub com 10 2006 Gasket Thermostat I Housing Temp Gauge Sender Early 3 bolt and Later 2 bolt Thermostat Housing Gasket styles Opel GT Heater Components and Connections A functioning heater system requires correct hose connections full motion operation of the control cables and the need to periodically clean out rust and dirt build up from the heater valve and heater core See Also Prior OMC Blitz articles on heaters which go into more detail on these procedures such as those of Nov 2000 Dec 1996 and Oct 1994 Heater Tubes These metal tubes to the heater core protrude about 2 inches into the engine compartment and often rust from the inside out If a leak develops on the interior passenger side floor check gaskets from the tubes to the heater core Heater Hoses As shown below heater hose widths are 5 8 and aftermarket hose clamps work better th
7. e Up Tech Tips at www opelclub com Carb Water Choke 90 degree elbow on hose and tee connections when upper 5 8 heater hose installed Use a pre formed hose f here to prevent kinks see p To Upper Radiator Hose Thermostat Housing Heater Valve on upper 5 8 heater hose Heater Control Cable amp Lever on Valve Valve is open when lever is toward front of car 1 C Y Water Pump Metal Tubes to Heater Core Notes Drawing Not to Scale Arrows indicate direction of coolant flow www opelclub com 10 2006 Opel GT Better Living Through Chemistry Sometimes you just don t have time to perform a complete repair Sometimes you can live with the results of just adding a chemical from a bottle Here are a few products that we ve found that can help Redline Water Wetter Coolant Additive Available from better stocked parts retailers and from performance vendors such as PAW this is a surfactant which treats internal cooling system surfaces Opel owners have reported a 10 to 20 degree temperature drop after adding this to coolant It s not cheap one bottle costs about 8 00 and needs to be replaced whenever coolant is flushed or changed Permatex High Tack Gasket Sealer Available almost everywhere the advantage to this sealer is it is so sticky that it holds gaskets in place while you are fumbling around trying to thread small metric bolts into ha
8. maximum as S T h mi 1 2 deflection 1 4 in either A R in r direction at the midpoint __ Q IIN gt A jamant between the fan pulley and the Upper Adjustment if a a alternator pulley Pivot and 13mm Nut Alternator Arrows alee ep Indic te ivot and 13mm Nut P direction of rotation of crank pulley Al and belt ternator wow Bushings a a www opelclub com 10 2006 Opel GT Thermostat and Thermostat Housing Thermostat installation and operation is critical as an incorrect heat range or a non opening thermostat will overheat and damage your engine Experience has shown that the best heat range is 160 degrees when it is above 80F degrees outside and 180 degrees when it is under SOF degrees outside so many owners change thermostats twice a year in each Spring and Fall Only use 192F Thermostats in exceptionally cold weather and quickly replace them when weather warms up ALWAYS test thermostat drop into a pan of hot water on a stovetop and use a thermometer to verify it opens within specified heat range prior to installation Never compromise with a cheaper model thermostat and for additional protection consider a fail safe type from motoradusa com or a balanced type from performanceunlimited com Also consider drilling a 1 8 hole in the thermostat s outer ring so sys tem can burp to eliminate air pockets when it is being filled Removal
9. ntly and that it seems to also color dye your entire intestinal tract Not for the faint of heart Use only as directed and if you somehow manage to choke down the entire bottle your mind WILL be changed o SE Perna HIGH TACK fSKET SEALANT rE m shell rls Se a D 4 m p s STORE lt r LCLINDER FORO ain Does enus Hewat E bi Cais OPEL MOTORSPORTS CLUB OMC is an independent US based auto club that specializes in German made 1968 1975 Opels OMC was founded in 1980 by Opel enthusiasts who wanted to share information and promote their marque in motorsports A newsletter was established to promote Opel events report Opel related news provide technical tips discuss vehicle upgrades OPEL MOTORSPORT CLUB and give members a free place to advertise New Full Memberships receive A year of b monthly print issues of OMC newsletter The Blitz a roster of club members an OMC decal and a window emblem Members can also participate in local OMC chapter activities held all over the USA OMC Newsletters THE BLITZ Print version black white Online in color OMC Activities amp Annual Meeting Opel Motorsport Club is the longest established Opel club in the U S A Members travel great distances to attend the OMC Annual Meeting a mid Summer gathering and display of classic and restored Opels Benefits of membership also include information from other Opel owne
10. ny upgrade should fit within the dimensions of the upper and lower tanks to avoid contact with the spinning fan and installation of a petcock for drainage should be considered There is also a firewall mounted triangular pressure bottle system enlarger connected by hoses to the upper tank and heater ports of fuel injected GT s that is sold on the aftermarket in Europe Mounting Radiators require connection of the lower mount bracket using the stock 13mm head bolt to prevent the fan from clipping the fins There are also 2 side rubber bushings and a lower bushing to hold its bracket in place To remove detach lower bolt swing the lower bracket and lift radiator out The under hood rubber weatherstrips help to direct airflow through radiator Drape the thin overflow tube down amp away from nearby front suspension arms Fan Shroud GT s originally had a detachable black plastic fan shroud some reproductions are done in fiberglass with a 15 wide opening Shrouds cool about 10 to 20 degrees but require annual inspection of the motor mounts and transmission mount to prevent tips of moving fan blades from striking the in terior surfaces of the fan shroud Make sure the shroud is upright there s a central mark on top and the part number is at the bottom When a 14 fan blade cannot be aligned within a 15 shroud also check the motor mount brackets the passenger side bracket has a slightly longer mo
11. ote a mixed metal electrolysis reaction at the gasket Fans Two fan styles were originally installed Early GT s had 5 blades amp later GT s 1971 73 had 7 blades Both were black plastic about 14 tip to tip and lightweight 10 to 15 ounces Some aftermarket fans had 6 blades as did 1975 s EFI clutch fan Generally the more blades the noisier the fan is but better cooling is also provided Belt The fan belt drives the water pump but if it 1s excessively loose the car may overheat There were 2 fan belt lengths with the early size for the cast iron lower alternator bracket with its 6 1 4 upper bracket and the later 1971 73 size for an aluminum lower alternator mounting bracket with its 5 3 4 long upper bracket Often overlooked the rubber upper and lower alternator mounting bushings are critical to securing the fan belt correctly Correct adjustment is when the belt will deflect about 1 2 inch total measured about halfway between the fan pulley and the alternator To do this the 13mm nuts on the 2 bolts holding the alternator to the brackets should be loosened and the alternator carefully levered away from the engine a long rod or crowbar works well when pivoted on the engine block then the 13mm nuts should be tightened while the alternator is in position i Alternator f E p a Bushing ___ a a Fan pulley Fan Belt Adjustment aD SR a l 7 _ Tighten Fan Belt to a
12. ould install the pre formed hose with the 90 degree bend to avoid kinking universal hose Water Pump if its age is not known or is older than 4 years or when the pump is starting to wear out Radiator Cap if rubber ring is worn or if cap cannot hold on a pressure test of 13 to 14 Ibs Coolant install about 1 1 2 gallons of a 50 old style green color anti freeze to water mixture Thermostat see separate section on thermostat on thermostat options testing and installation Pressure Test System This means having a shop test the radiator and heater core for leaks and the radiator cap Additional related components include inspection and replacement about twice a year or when otherwise warranted of the motor mounts and transmission mount Also check the alternator mount brackets and upper and lower bushings and either install an internal screen like the aftermarket Gano filter shown at right sold online on the upper radiator hose or clean out dirty rust from the heater valve about twice a year Keep date mileage records when installing parts to determine component wear rates DT When changing head gaskets always install the rubber o ring on engine block before setting down the cylinder head Gano filter screen l mon i i i Monitor cooling system performance on the GT temperature gauge The needle should read between 1 3 to 1 2 of the way to the red part of the gauge About 176 to
13. r is on the tech tips section of OMC s website at www opelclub com www opelclub com 10 2006 Opel GT Radiator Stock 1 9 Opel GT s were factory equipped with a 2 row core brass radiators which performed well in Opel s native Europe but have proved only adequate for some conditions in Summer in North America The factory GT radiator did not have a drain petcock valve so draining and removal required detachment of the lower radiator hose On GT s with automatic transmissions the lower radiator tank also had a transmission fluid cooler accessed via two screw in ports for flex hoses It is important to have a very good condition radiator with very good flow and good contact to the metal on the internal surfaces Over time the internal rows get clogged and the brittle exterior fins trap debris or get bent when the car battery is removed When a radiator can no longer be serviced by a chemical flush at a radiator shop or a higher performance engine or air conditioning system is to be installed then replacement of the stock sized radiator core should be considered approx 13 3 4 tall by 12 3 4 across by 1 3 4 wide Upgrades Include a heavy duty denser brass core with more fins per square inch and 3 rows of dimpled tubes for greater cooling Unfortunately no aftermarket aluminum tanks are made for the GT so only a custom build could be installed never mix brass tanks with aluminum cores A
14. rd to reach and unseen holes This is especially helpful when doing side of the road emergency repairs like a water pump replacement True it s not as expansive as Silicone RTV but you don t have to wait for up to 24 hours for that sealer to complete cure either Only drawback This sealer drips and leaves spiderwebs of gooey burgundy colored traces where you work Wipe off quickly with rag or a paper towel and WD 40 Silver Can of Engine Restorer This stuff worked really great on a 4 cylinder engine which had 2 cylinders with very worn piston rings Compression rose in the lowest cylinders from about 90psi to about 140psi which was almost even with the 2 good cylinders on that engine Do the Compression Checks to make sure you don t have a valve problem to make sure it s worn piston rings and this 7 00 can could give you 1000 s of additional miles on engines that are otherwise toast Warning Check for THICK engine oil when you buy Opels lIt could be this stuff Sta Lube 140W Gear Oil You can t just buy a rebuilt Opel 4speed manual transmission or a rebuilt Opel rear axle anymore In fact with the UPS costs of shipping these heavy items sometimes you re better off just finding a way to keep your used but still functioning gearboxes and differentials still running Consider the Sta Lube 140W gear oil Sold by NAPA stores it mates to the accessory pump hardware and once you manage to force quart
15. rs on the maintenance and improvement of their Opel s and the ability to contact fellow members on their common interests Opel Motorsport Club funds help maintain our website with helpful Opel information at www opelclub com OMC s peer reviewed technical information helps owners avoid common and costly errors on Opel repair jobs OMC is officially recognized by the Opel factory of Russelsheim Germany and OMC SOLO II racing activities are also sanctioned by the SCCA Sports Car Club of America for racing nationwide in the USA Full U S Membership 45 00 Includes bi monthly b w print issues of The Blitz postage amp benefits listed above Online O nly Member 20 00 Includes downloadable Acrobat pdf version of The Blitz for home color printing To Join Send your name amp address with check money order payable to Opel Motorsports Club by mail to OMC Treasurer 3824 Franklin Street La Crescenta CA 91214 1607 OR Send 47 for Full US Membership or 22 for Online Membership via PayPal to JonQMC opelclub com International Members Please Add 10 for Full Membership to cover additional postage costs
16. s of this honey goo in it significantly quiets the whining and howling of worn gears Don t mistake the common multiviscosity 85 140W which doesn t work as well go for the straight 140W only Rain X Not Shown Smear this on your windshield once every 2 weeks You can drive in the rain without turning on the windshield wipers which never worked that well anyways Polytuflon Green Grease Polyurethane Lubricant Sometimes your polyurethane bushings in your front suspension squeak but you don t feel like removing them again to re coat with Teflon Back in the 70 s Quickor Garage of Oregon used a paint can shaker machine attached to some front end control arms to develop a goopy green grease that they said outlasts all other lubricants on poly We used it when re installing some front end poly bushings and so far it works well with no squeaks Costs about 10 shipping from Ebay ID Suspenstech or by email at quickor at comcast net Brainwash Mental Lubricant Sometimes when the stress of chasing down obscure mechanical issues on a 30 year old car becomes too great it s time to re boot your consciousness For that try a cold bottle of Brainwash by Skeleteens of L A We re not sure exactly what s in it mad dog weed but the label assures us this may be your only way out We have observed that just a drop spilt will ruin clothing and porcelain items permane
17. tion which will last virtually forever Reproduction heater control lever cables are now available as well Water Choke Hoses and Fittings When Installed The 1 9 Liter engine Opel GTs from 1968 to 1972 were equipped with Solex 32DIDTA carburetors which had a water choke and which connected by thin 5 16 hoses such as fuel line and 2 aluminum T fittings to the main 5 8 heater hoses Because they ran poorly after being subject to heat most Solex carbs have been replaced by the Weber 32 36 DGV series The Weber 32 36 DGAV version had a water choke but it came with a too large 5 8 wide hose fitting which was bulky and didn t fit the factory tee fitting hardware and which also decreased coolant pressure through the heater so many GT owners installed the smaller 5 16 hose sized water choke adaptor in its place There 1s little advantage to operating a water choke on an Opel GT except where air temperatures when driving are frequently below 45F degrees One advantage to the electric choke Weber 32 36 DGEV carb is that there are less hoses under the hood and it is suggested that the tee fittings be removed from the heater hoses to increase coolant fluid pressure to the heater and to give a cleaner under the hood appearance Try to avoid confusing heater hoses with engine vacuum hoses See also OMC s Vacuum System Operation Guide as included in the June 2006 OMC Blitz or online as part of Engine Tun
18. unt hole location than the driver s about 5 from centerline to engine block on pass side com pared to about 4 5 8 on driver s side An intact front grille on the car also helps screen road debris from lodging in the radiator fins An coolant overflow tank is also recommended especially for GT s with air conditioning systems None mairi M otau Heng sa a er a nar puai i N KOHLER Above Cooling System Enlarger for higher performance Opel GT engine applications From Europe Upper Tank Core Lower Tank Heavier Duty Radiator Cores with greater fin density and a 3rd row for greater cooling Above GT Radiator Mounting Hardware shown images not to scale Left Opel GT Radiator Shroud Provides greater cooling when installed www opelclub com 10 2006 Opel GT Water Pump amp Connected Components The water pump is the heart of the Opel GT Cooling System Because they turn at a higher speed ratio compared to the engine Opel GT water pumps average about 3 to 5 years of service life Damaged and unbalanced fans and worn out alternator bushings are the main premature killers of ir Opel water pumps When the antifreeze is neglected or corrosion accumulates its internal bearing seal ar Y wears even more quickly If the front shaft of the pump shakes easily when you grab the center of the fan and tug up and down or if fluid starts to leak out the weep hole
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