Thread: GTP: A few Coolant problems

98 Grand Prix GTP

First problem: Coolant leak at what looks where the throttle body meets the supercharger housing. Now I just removed the throttle body to clean everything out. I didn't notice a leak before that. I assume that I need to change the gasket. However, should there be coolant in that area even with a gasket? I thought only air should be passing through there? If there is another leak behind the throttle body how do I tell where it's coming from and would I be able to change the gaskets of the supercharger or would I have to repair/replace?

Second problem: Just yesterday my car started overheating. It was also the day I removed the throttlebody and noticed that leak so it could be related. However I'm getting no heat and a cold radiator. Hot upper hose and relatively (for being next to unshielded headers) cold lower hose. From what I know these are classic signs of a blocked cooling system. So i just back flushed until i got clear water from both top and bottom of the radiator. The fact that there was water coming from both sides of the radiator leads me to believe there is nothing blocking it. I have a relatively new 160* Tstat also. So I go to refill it and I can only get in about half a gallon of coolant before the radiator starts overflowing. I drain it again, close the cap and pop the Tstat housing and try filling from there but get the same results, I can only get about half to 3/4 a gallon before it starts backing up on me. Unlike the leak I always noticed this problem. I just thought I was misjudging how much coolant I had but after flushing I would think I would be able to get atleast 2 gallons in there

Any ideas?

I have searched the forum for the answer but only saw answers that applied to NA grand prixs, and since the SC replaces the upper and lower IM I need an answer that is specific to the GTP

sorry I meant 180 Tstat not 160

I am running a few mods and a 180 was suggested over a 195

I never pulled the lower rad hose I let it drain from the drain plug...should I have or would that suffice?

also the gasket you are referring to, that would go between the TB and the SC? Or somewhere else on the TB?

Alright, I appreciate the fast help. If autzone has it Ill do this tonight by candle light. If not ill try it early in the AM

One more question. Since this gasket is failing. Is the coolant leaking internally also? Am I getting coolant sucked into my blower? I only ask to know if it's OK to drive to the dealership in the morning or should I just let it sit till I replace the gasket. Last thing I want is a hydro-lock situation

I can't find the part listed at autozone and I don't have the time to wait for it to be delivered. So to the dealership i go.

Idk if anyone on here has experinced the issue but thermostats are cheap and can come bad. Not likely but possible. Also, did u just run water through the rad or through the motor too? Cuz u werent specific. Probably should've ran water through ur heater core hoses too

Originally Posted by bps02gtp

Idk if anyone on here has experinced the issue but thermostats are cheap and can come bad. Not likely but possible. Also, did u just run water through the rad or through the motor too? Cuz u werent specific. Probably should've ran water through ur heater core hoses too

I backflushed, which means i flushed through the inlet hose and it came out of both sides of the radiator.
As for the thermostat, I hadn't checked it, and I should check to see if it opens. But i figured since the top hose was hot there was coolant going through there

Originally Posted by BillBoost37

Dealership isn't likely to have it either. Call ahead.

As for the local places having it... they should be able to have it same or next day.

No one had it so I went with closest GM place that would let me next day order over the phone. I should have it installed by tomorrow afternoon and I'll update on how it's running