Thread: 2006 Grand Prix running hot

My son has a 2006 Grand Prix 3800. He has only had it a few weeks, but it had been sitting for a couple years before he got it. We have flushed the coolant system , replaced the fans and the thermostat, but it still runs pretty hot. Anything else we should check?

Did you follow the proper cooling system bleed procedure? These motors are prone to air pockets that will cause the temps to be all over the place.

Beyond that the fan settings are around the 200* mark. Can't remember the low and high settings off the top but they may seem high if you're new to the car. The other thing that can effect it is the Coolant Temp sensor.

I have had 4 GP’s and they all seem to run hotter than I would have liked.


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Bleeding the system is key, and can take a couple rounds and pulsing hoses to get it right. You should see it get to around the 195 thermostat mark, and only get about 15-20deg higher under traffic/etc. conditions, and when using the A/C for long stretches. Also, if the car overheats too much, some thermostats can lock open and no longer regulate the coolant flow.

The water pump will usually weep out the front as an indicator of failure, but other issues also happen. Any sign of a leak after it's closed up needs addressing.

Radiator fans supplement cooling some, but with the stock settings and 195 degF thermostat, they usually only kick on at low speed for most operating conditions (I'd have to dig up stock settings to see what they were).

Good luck, and hope you get it settled out.

Watch for blown head gasket. I my son's car ran hot too. I had hoped it would last until he was out of college...but he's taking longer to get out of college than I wanted.

$2400-2800 to replace the head gasket.

Anyone need a parts car?

I'd test the cooling system for exhaust gas before jumping to a blown headgasket, especially on these motors since it's just not that common. It does happen but it's not very often unless it's been overheated a bunch of times.

If it truly is a HG then I'd just yank the heads and replace the gaskets and headbolts (they are TTY bolts) and call it a day. Can be done with basic tools other than the torque angle meter needed for the headbolts. If done yourself will come in way under that $2400 mark.