Over heating but AC wont turn off?


Asked by Jun 06, 2015 at 06:00 PM about the 2005 Pontiac Grand Prix GTP

Question type: Maintenance & Repair

I have a 2005 Grand Prix GTP. I went to pick up my son from daycare the other day
and heard what sounded like my tire losing air at a rapid pace. I went around the front
of the car and noticed I could hear it better standing at the front of the hood. I waited a
minute and opened the hood to see coolant dripping down from the hood up near the
reservoir. I didn't drive the car again until today when I was going to pick my son up
from his dads house HOPING it couldn't over heat and I could just let it sit after that
until I can get it fixed. But as I was driving the temp gauge was continuing to rise so I
attempted to crank my heat full blast. instead of heat though all that came out was
freezing cold air. I had the temp up at 90 on my thermostat on the dash. The car
started to over heat and my display told me it was going to turn off the ac to help. So
the ac turned off and my car stopped making it's way into the red zone and started
cooling down pretty fast.
Have any idea what could cause this?

2 Answers


Sounds like you're very low on coolant due to a leak. You were right by turning on the heat but you got cold air due to the low coolant. Your automatic climate control runs the air conditioning system full time to dehumidify the air in the passenger's compartment even when heat is selected. This helps prevent window fogging on cool damp days. Because the a/c system puts an added heat load on the cooling system the computer will shut it down if the engine starts to overheat. Refill the cooling system and check for leaks. I suspect a hose or possibly the water pump has sprung a leak. HTH. -Jim


There are a couple of small plastic elbows that take coolant to the heater core. They all fail eventually and you loose all your coolant. That is most likely the problem. The parts are about $5. Shop/do-it- yourselfer time is about 2 hours and of course you'll need new coolant. In the mean time don't run it for more than a few minutes at a time or you'll overheat the engine and wreck something.

1 out of 1 people think this is helpful.

Your Answer

Add photo

Related Questions

  • Slight over heating while idling?? Do I have a problem? 41 answers

    I JUST bought a used 05 pontiac grand prix, 140k miles, 3.8 engine. was driving it around last night for only the second day, and left it idling in a parking lot for about 30 minutes while the pe...

    2005 Pontiac Grand Prix


    Maintenance & Repair

  • ac clutch not engaging 1 answer

    My ac blows hot air. Clutch not engaging. Tried adding a can of refrigerant, cooled off a little but the clutch still did not engage

    2004 Pontiac Grand Prix GT1


    Maintenance & Repair

  • The heat in my 07 Pontiac Grand Prix gets warm. not warm enough where its comfortable though. 1 answer

    The heat in my 07 grand prix blows out warm. just barely warm tho. almost cold. The light on the control panel to turn the AC on cold stays on and i cant get it to go off so the compressor is running ...

    2007 Pontiac Grand Prix Base


    Maintenance & Repair

  • 2008 GrandPrix no heat/no ac - has coolant and refrigerant what could be wrong? 19 answers

    It started last year, I checked the refrigerant and it's full. This past weekend I checked the coolant an it's to the top of the cap. I Google the issues and a lot of people out there seem to be havin...

    2008 Pontiac Grand Prix Base


    Maintenance & Repair

  • Broken ??? Connected to AC Compressor 8 answers

    Hello club members! I just purchased a non-running 87 Base Fiero for $300. I was told that the last time it was started all kinds of fluids shot out from under the engine so the previous onwer turned ...

    1987 Pontiac Fiero Base


    Maintenance & Repair

Search Pontiac Grand Prix Questions

Pontiac Grand Prix Experts

#1 Js08016
Reputation 3,690
#2 Tom Demyan
Tom Demyan
Reputation 2,450
#3 munron
Reputation 1,960
View All

Related Models For Sale

Used Chevrolet Impala"
937 Great Deals out of 35,696 listings starting at $1,500
Used Pontiac Bonneville"
3 Great Deals out of 859 listings starting at $2,950
Used Dodge Charger"
647 Great Deals out of 29,677 listings starting at $2,275
Used Pontiac Grand Am"
1,981 listings starting at $1,995
Used Pontiac G6"
144 Great Deals out of 5,591 listings starting at $999
Used Chevrolet Monte Carlo"
12 Great Deals out of 2,062 listings starting at $2,000
Used Chevrolet Malibu"
1,154 Great Deals out of 73,046 listings starting at $695
Used Pontiac GTO"
13 Great Deals out of 515 listings starting at $6,500
Used Ford Mustang"
739 Great Deals out of 41,066 listings starting at $900
Used Nissan Altima"
1,357 Great Deals out of 87,467 listings starting at $1,095
Used Nissan Maxima"
495 Great Deals out of 24,226 listings starting at $1,500
Used Chrysler 300"
582 Great Deals out of 20,787 listings starting at $1,490
Used Honda Accord"
1,265 Great Deals out of 78,694 listings starting at $1,400

Used Cars For Sale

2005 Pontiac Grand Prix GTP For Sale
54 listings starting at $3,000