Grand prix heat off and on also, drinking coolant?


Asked by Jan 21, 2016 at 09:55 PM about the 2002 Pontiac Grand Prix SE

Question type: Maintenance & Repair

02 grand prix 250k miles. Really weird situation here, what it does is the
gauge will act normally and produce heat normally. All of a sudden it flies
up and down slowly almost overheats but doesnt. Then the gauge will
come back down all the while me having absolutely no heat. What ive done
before is add coolant (dexcool) And it will stop, it will produce heat, and act
normally for about two weeks. Now ive noticed no physical spiils on the
ground and the oil isnt milky. It needs changed but isnt milky. any ideas???
im at a loss here...

3 Answers


Wildly fluctuating coolant temperatures would indicate to me that you have a bad thermostat.

1 out of 1 people think this is helpful.

When it starts the fluxuations is when it is running low on coolant, the most probable cause is a blown headgasket especially with that kind of mileage. I would recommend performing a block test, that will confirm that exhaust gases are present in the cooling system.

1 out of 1 people think this is helpful.

Since this is a SE model I'm assuming you have the 3.1L V6. They blow head gaskets. But before you condemn the motor, at 250,000 miles the head gaskets should have been done already, long ago. With the engine cold pressure test the cooling system. You may have a seeping hose, water pump, radiator, or heater core. The cooling system should hold 15 PSI for a minimum of 15 minutes. If not it's leaking somewhere. Also pressure test the radiator cap. It may not be holding pressure. That can cause a "sneaky" leak as well. HTH. -Jim

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