tjbreen

I had trouble in July with my car overheating at Watkins Glen. It was hot (98) but other modified 944Ts were not overheating. I have an all aluminum Griffin radiator and had just done the waterpump, thermostat, belts etc. but could not keep it cool.

The top of the radiator was very hot on the drivers side but I could hold my fingers on it on the left side. Also, the lower hose was not that hot. I checked belt tension and it is good but I suspect that the thermostat is opening, but not fully. Both fans run on high but only the drivers side is blowing hot air, the passenger side fan air is barely warm. The car will maintain 180 degrees at idle with both fans on high.

Does anyone have an idea about how to check if the thermostat is fully opening? Can another Griffin radiator owner comment on whether their entire radiator gets hot or just the drivers side during an extended idle?

ninefiveone

I don't have the Griffen radiator but I do have the aluminum radiator/oil cooler that Chris White sells.

We've been chasing a similar problem on my car. Chris has a theory that the radiator may work too well. Since the thermostat is on the incoming side of the coolant loop, the coolant coming from the radiator may be too cold to allow the thermostat to fully open.

tjbreen

The too cool theory seems reasonable, given the data I have collected. When I start the car from cold and put one hand on each side of the radiator, both get hot until the fans kick in on slow. Once that happens, the passenger side cools down quickly then the fans go to high and the passenger side cools down even more - to about ambient and the drivers side becomes too hot to touch. If overly cool coolant were passing over the thermostat, it would have to close down holding even more heat in the engine causing the input side to get even hotter, which is what I observed.

Something that would help, but not cure it would be a lower temperature thermostat. This would just hold open a little more or a little longer. I am going to test the too cool theory by disconecting the cooling fans while parked to see if the lower hose gets hot, then plug them back in one at a time to see what happens.

This may be an example of an upgraded part creating an imbalance in the system that actually causes things to get worse, not better. The cure may be to go back to the less efficient stock radiator, which was designed to work with the incoming side thermostat.

ninefiveone

Please report back what you find, I'm hoping for a solution that doesn't require going back to the stock radiator. I'm hoping a cooler thermostat does the trick but I know the cooler thermostat isn't much cooler (80C standard, 71C cooler).

Scott H

I want to say someone posted a similar thread last week or the week before (or it got bumped). The consensus was that the replacement t-stat didn't open as much as the one that it replaced.