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2006 Grand Prix overheating

08-27-2010, 08:56 PM
My Grand Prix recently began heating up very quickly if I'm stopped in traffic for several minutes or going through a drive thru, almost going into the red. Once I get moving again though, and the car is getting airflow, the temperatures quickly return to normal. When I got home today, I popped the hood and saw that the radiator fans were only running if the AC was on, but at that point the temp was normal....

I'm hoping it might be as simple as a bad thermostat.

Any ideas of what the issue might be or is there more information I need to give out?

Also on a somewhat related note, I noticed my coolant resivoir was low, so I added some dex-cool (about half the bottle) but forgot to mix with water, How bad is that? Should I drain and refill the cooling system?


08-28-2010, 09:44 AM
Welcome to the forum!.

You should check the thermostat maybe is getting stuck, it is located after the upper radiator hose and you mentioned the fans won't turn on, only with the A/C maybe the electrical switch to the fans has gone bad, I'm sorry I can't help with this since I don't know where it is located on your car, Hopefully someone more skilled will see your post. These guys are real good trust me!.



08-28-2010, 07:28 PM
How many miles do you have? Have you checked the coolant level in the radiator? Is the heater blowing hot air?

08-28-2010, 07:51 PM
Check coolant level when cold, and a 50/50 mix of antifreeze protection,
Also coolant system might need tobe purged.

08-28-2010, 09:16 PM
Make sure you use distilled water when you mix or purchase 50/50 pre mix. Dex-cool don't like tap water...

08-29-2010, 08:31 AM
The OP should post either the model or engine size on this year GP but assuming he has the SIII 3800 engine the thermostat is located in the same location as the SII 3800 engine. Just follow the upper radiator hose to the end at the lower intake manifold and thermostat housing. The component that controls the cooling fans is the PCM module through cooling fan relays and the ECT (engine coolant temp) sensor.

To the OP unless you flush the complete cooling system out stick with the GM Dex-cool coolant mixed 50/50 with distilled water. I know of no issues with '04 and up GPs to include GXPs with Dex-cool so no bad mouthing Dex-cool posts. :nono:


09-16-2010, 06:32 PM
Thanks for all the input, I put a new thermostat in and everything is working great now.

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