Superformance coupes (and possibly others, I don’t know) tend to run hot owing to the lay down radiator and
oil cooler heat exchanger. Ever since I got mine, I have been concerned about both high coolant and
oil temps. When pushed (for instance, going up the twisties of our local 4000’ mountain in second – high RPM and low speed) both would get too hot – coolant up to more than 220 and
oil up to more than 230 degrees, which is marginal for engine life. The main reason for this is the oil “cooler” (actually called the heat exchanger in the parts list) transfers its heat to the engine coolant after the oil gets hotter than the coolant (all the time except when warming up), after which the coolant rapidly heats up too much. That’s why the new Shelby Mark II coupes have separate oil and coolant radiators, but they put the oil cooler below the pan between the lower front frame rails! I think there is a better solution.
My local Factory Five dealer/hot rod builder (they built the FF Type 65 coupe that set a class record of 216.9 at Bonneville in 2008 -
http://www.cardomain.com/ride/3168274) showed me a unit auxiliary oil cooler that comes complete with a puller fan mounted on top. It’s made by B & M (
http://www.bmracing.com) and its part number 70298. It’s the Hi-Tek Automatic Transmission Cooling System (10"x7-1/2"x4" with 7" diameter fan, $217.86). We installed one on the right hand side of the engine skid plate (the plate with the two engine bay cooling fans on it) in place of the right hand fan. You have to remove the temperature sensing switch that comes on the unit and plug the hole, and plumb the cooler in between the motor and the filter (not enough room for two more SS hoses through the front of the frame), but it fits well and requires no mods other than new holes to mount. It’s connected to the dash exhaust toggle switch just like the fan it replaces.
In addition, you can solve your cooling system air bubble problems. Weld a water neck on top of the thermostat housing with a high pressure cap (much more than the 16 psi on the header tank), and make a small bleeder (petcock) to fit in the coolant line running from the left top of the radiator to the header tank. You may have to reroute the line so that it runs steadily uphill to the tank. These two changes allow you to eliminate ALL the air from the system easily. You fill the radiator from the new water neck until the coolant is a little higher than the cap seal (that level is high enough to fill the bottom of the header tank), then put the cap on. Then bleed the remaining air out of the radiator top using the petcock on the left. No need to touch the thermostat housing cap until draining the system again.
Finally, if you are running the NAPA heater valve recommended by Dennis Olthoff in place of the crummy brass thing the car comes with, put a bypass line between the in and out heater hoses before and after the heater valve. It will help stabilize temperature fluctuations in the cooling system.
The combination of the auxiliary oil cooler, no air in the system, and Water Wetter with 30% ethylene glycol gave great results. For tests I drove all the way up the mountain (15 miles) on a 72 degree day in second gear (3-4000 RPM) with all three fans running (radiator and oil cooler). Coolant never rose above 200 and oil temps were no hotter than 220. To further test the system, on a 90 degree day I drove five miles up with everything running with the a/c on in its coldest position, and coolant was 210 with oil at or less than 220 degrees. Then I drove through town (stop and go at less than 25 for a couple of miles) and coolant did not go over 215 and oil was at 200.
Under normal circumstances on the highway (around 65 mph), with the oil cooler fan and radiator fans off, coolant stays around 180 (my thermostat) and oil is at 190-200.
I’m really pleased with these modifications, and I think this cures the cars biggest mechanical problem. Questions, comments, ideas, or suggestions?
David
SPC0123
How to stop coupe overheating problems
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