Mike Goebel

First off everything in the cooling system is new except for the radiator.
Bled the system twice after replacing all hoses, parts etc.
Fans seem to come on at about the right temp and function properly. Did the Clark's test too.
AC was on during overheating.
I don’t think the head gasket is blown as the car doesn’t overheat if the ambient temp if less than 80.


Here’s what happens:

IF the ambient temp is 80F or lower the car never gets hot, maybe will hit the ¾ mark after driving in anger.

When the temp is above 80F. After driving on the freeway in stop in go traffic for about 10-15 minutes the gauge will settle at about the halfway point between the first mark and the ¾ mark. Then it will abruptly drop a few times to the first mark. Then it will bounce a few times between the first mark and the halfway point between the ¾ mark. After that steady climb to the ¾ mark will happen. Once the red light came on before I did all the cooling system repairs. However after the repairs I turned off the car at the ¾ mark.

Is it normal for the water temp to hit the ¾ mark in those driving conditions?

Thanks
Mike G.

mj951

Not normal with my car, gauge pretty much sits at 1/2 mark once warm (half way between first and second line).
On occasion I've had the water temp gauge bounce erratically but could always clear it up with a good bleed using a pressure tester.

GPA951s

Did you replace the Actual "Gauge" sensor? Right after a rebuild My "Red Light" came on after 2 min of Running... Freaked me out... New Sensor... All ok..

Mike Goebel

No but I might as well even though the light only came on once about 6 months ago. I'm not sure these kinds of things can have intermittent problems??

Thanks
Mike G.

DarrenD

Have you verified the small thermostat in the waterpump is installed correctly? I had very similar issues and was losing my mind. I had installed the small thermostat as per a Porsche manual, turns out it was installed backwards. Once I installed it the right way, Fixed!! No more overheating.

Mike Goebel

Is that the auxiliary turbocharger pump? Not sure if it’s in there the right way I put it in the same way that I took the old one out. I’m also not sure what effect that has on keeping the engine cool.
Pretty sure I installed it as shown in this pic.




Thanks
mike G.

MAGK944

DarrenD is correct, PET is incorrect, I had the same issue once and it confused me. The spring on the second thermostat should face the engine and not the plastic elbow as shown in PET. So, if you installed it like the PET diagram it’s wrong.

PF

It is important to use the correct amount of shims between the snapring and the rubber seal for the termostat so that it seals against the WP housing. There are early And late housings wich affects the the spacing. It it is set up to loose water will get by and cause issues.

951North

Seriously!?! I did my WP this spring. There wasn’t an aux t-stat at all so I went by PET... also there was no seal between the main t-stat and the snap ring. Now I’m experiencing higher running temps also. Going to flip the little t-stat tomorrow. Kinda thought it weird the spring was on the cool side of the circuit.

Mike Goebel

Looking at the cooling system on Clarks it kind of makes sense that the thermostat should be installed as you say. Because installed backwards the coil springs would never receive hot coolant from the engine thus not opening and allowing coolant to pass through the turbo Well that means that the turbo could be overheated. Aaaaaaaaah!. That being said I've heard of people disconnecting the turbo water pump all together without problem, not that I think its a good idea!!!

Now why would that make the engine overheat? I mean the coolant is not flowing through a hot turbo so there is no heat transfer to the fluid so technically the fluid should be cooler??? Huh?

Beer30 time.

Thanks
Mike G.

951North

Now I’m not convinced PET diagram is wrong... looking at the Clark’s diagram again. The TC has a pump to circulate with the reservoir operated by a thermo switch. If that circuit gets too hot then the aux t-stat opens by heat conduction down that hose. Then the hot coolant would be circulated through the main radiator.

MAGK944

Here’s another comment from a trusted source about the PET being wrong, refer to the comment at the end of the tech article and the reply by Nick at Pelican: Additional Thermostat Replacement Procedure.

GPA951s

I Don't Run a turbo T-stat on my cars, I drive them in the summer only. Think about what i happening on startup, Everything is at the same temp, and when hot.. Again with T-stat open Just coolant circulating..So to me there is no point in running it if I never drive it in the cold... . I think the original intent for the turbo t-stat was to allow the coolant that is in the engine to stay there until operating temp is reached for colder climates... I also Don't run the "Sealing ring" around the main thermostat so when the system gets filled there are no pockets of air, it purges better... MY .02

MAGK944

I know a few guys who do the same thing and what you say is valid, however it’s probably wise that the op gets everything working as it should in the stock configuration to bring confidence that all is how it should be before starting to omit parts.

In my case fwiw reversing that smaller thermostat fixed an issue I was having. I have also had an issue caused by the main thermostat being an incorrect “match” for the coolant temperature sensor. Apparently there are three different types (temp settings) for both of those parts and if you get them wrong all sorts of hot running issues can occur.

Anyway, not saying any of these are the op’s issue, just saying what fixed my running hot problems in the past.

Chapman951

I have a coolant coming from this location. It was not severe enough to make drips. It would sit on the block (think it’s the block) and evaporate. I only noticed by chance. I was losing a small amount of coolant but enough to cause my temperature needle to rise in the 3/4 zone instead of hovering around 1/4 - 1/2.