DeWolf

Pull the radiator and and get the tanks removed and the core cleaned. I had a 944NA that was overheating at lights (like into the red) and it turned out the core was almost 50% blocked. After the clean, 40C Adelaide summer, with the a/c on and it stayed just a tad over the first mark. Once moving again it dropped just below the first mark.

gt37vgt

the thermo stat stops hot water leaving the engine when it is closed the water hits the thermostat then enters the bypass port in the center of the thermostat housing . when the thermostat opens the the valve in the thermo stat moves inward and covers the resirc port so less or no water can resirc.
In the absense of the thermo stat the water will takes the path of least resistance back through the motor not your semi clogged rad .
if you choose to pull the thermo stat . block the 1" hole in the center 2.5" thermo stat housing


Chris's photo of the oil thermo housing hmmm yuk it seems to me that this coolant in there does not realy flow .. Chris any tip's on that mate ?
i was thinking of drilling the ports in and out 2mm bigger ..

Luis de Prat

Wasn't implying that it was causing anything. Just stating the stock configuration, as many cars are missing these panels.

Duke

Oh yes, but not "between the bat wing and the crossmember" as I wrote
That tray is mounted after the crossmember. And that one is even more rare to have left on old cars than the plastic tray!

Luis de Prat

Although I agree that the overheating situation being discussed here should not be caused by the undercarriage features, i.e., engine pans, there is still something to be said for the way the batwing-front tray-rear aluminum pan combination work together to move air below the car and up into engine compartment for improved aerodynamics and cooling.

Keep in mind that when the 951 was designed, Porsche had already benefitted from extensive wind tunnel experimentation by Norbert Singer on the 956/962 race car chassis, which led to significant developments such as the rear air diffuser which found their way into the street cars in varying degrees of functionality. The undercarriage fairings on the 951 are no exception.

Yes, when you have both on the car, a nice feature I've found is that both can be removed together as a unit, saving considerable time not messing with extra mounting bolts. This is done by leaving the bolts with speednuts in place, and just removing the phillips heads at the front of the plastic tray, the 2 10mm nuts holding the aluminum pan on the sides, and a couple of the plain 10mm bolts that thread into the crossmember in the middle.

333pg333

Thanks guys for all the tips. Most beneficial. I'm sure we'll have it sorted in the next day or so. Shall report back.

DivineE

I'd have gone with a lack of flow as this sounds very similar to when my water pump failed but your white smoke and steam from the bleeder comments make me think head gasket.

Either way best of luck sorting it out and hope you get it running right again soon. Let us know when you solve the mystery?

Chris White

I could tell you what I do for the 'serious' motors...but I night have to shoot afterwards!

It has something to do with the 2 holes you mention.

JET951

Hi guys,
i pulled the black 86 radiator and compared it to patricks 89 radiator, which is much newer. the radiator from the black 86 which is the radiator which is in the car when it overheats definatly has signs of blockage. as you can see from the two pictures there is a build in the old radiator.

comparing them when blowing through. the newer one has very little to no restriction, where as the 86 feels like blowing up a baloon that is already inflated. im not sure how to exactly measure the resistance. We realise this could be the problem as to why Pats car is overheating but it is very hard to test on the street because of the need to be on boost for a good amount of time. so i am playing with the idea of replacing the headgasket as well.

i removed the water pump and it is fine.

Van

Great pictures Sean!

gt37vgt

yeh nice one be great experiment for one of those radiator flush products ..

333pg333

So the question is do we think this is enough or should we just do the head gasket while we're in there?
On one hand you want to know what is going wrong so by doing both and it works, then we may not really know what was causing it. By only changing the radiator and hopefully being able to satisfy ourselves that we can 'test' it on some deserted street, we may fix it, but then either it may not overheat on the street and we won't know if it's fixed, or it may overheat and then we've got to go back in and do the headgasket??

Also if it is the h/gasket this might be a re occurring situation based on headlift due to running 1.5 bar on E85? So if we wind up doing the h/gasket now, should we install some ARP studs? Why are these considered superior to stock studs anyway?

btw, this Cometic was replaced probably less than 9 months ago....coincidentally after our last visit to the same track.
The one advantage of these metal headgaskets are that you can actually drive home from the track even after blowing these at the track.

A.Wayne

was this engine a good engine before or was it repaired !!!!!

gt37vgt

well if the rad is a bit blocked it would get worse with the thermo stat out as the rad would be far more restrictove than they by pass port .
and i still think keeping a head gasket in tact is much more about tuning and thermal management than it is about studs ..
still bugger all real accounts of OEM stud failure

333pg333

The engine was good...but it was in an accident that caused us to swap it into another car due to the original one being pretty bent up. A rapid loss of momentum can have an effect on not just the human occupants, so I s'pose there is a chance that something else was affected?

The temps didn't really change when we took the t-stat out. As for h/g's, well there are a few people that have had issues with headlift on our cars at high psi. Not sure what high is any more, but relative to our cars perhaps it's over say 24psi. Even though our headstuds are significantly larger than that off most 911s (if not all?) there is obviously a demand for aftermarket products. I'm not sure if anyone can point to their superiority though? I know some makers definitely re tap the head/block to take larger diameter studs. They must be doing this for a reason??