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Canadafix, Canadian Certified Interprovincial
Category: Pontiac
Satisfied Customers: 1632
Experience:  Certified Canadian Class A technician since 1989
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2004 Grand Prix: overheating..the water ran..running rough

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2004 Grand Prix began overheating this week, my husband changed the line (as it had a small leak), then he also replaced the water pump, as well as a fan sensor(?). The car ran for him last night when he took it on aXXXXX- it was running rough but not overheating but then this morning, during my commute besides running rough it also began overheating again. The reserve tank is completely full, but the radiator cap seems low. Can anyone shed some light on this, he is talking about junking it and I love this car.
Hello and welcome to Just Answer.
My name is XXXXX XXXXX I will try to help solve your overheating problem.

When the vehicle gets hot, does the cooling fan run?
Have you noticed any other symptoms such as no heat from the interior heater?
Does it overheat more when driving around slowly or at highway speeds?

There are a couple of possible issues here.

The running rough does concern me here. The reason for that concern is that you may have a bad head gasket which could cause the rough running and the overheating.
If a gasket is leaking some of the explosion that takes place within the engine into the cooling system it pushes out coolant and leaves some of these gases inside the cooling system causing the overheat.
This problem can be tested by a mechanic that can test for any of these gases coming out of the cooling system using a tool which holds a special solution that changes color when these gases are subjected to it.

Next, it could be a partially plugged radiator. A plugged rad restricts the flow of coolant or doesn't provide enough heat to escape.
In this case your rough running will likely be caused from something else.

If you have further questions on this subject please reply here and we will continue.

Thank you.
Customer: replied 6 years ago.
When the vehicle gets hot, does the cooling fan run? I am not sure about the fan running.

Have you noticed any other symptoms such as no heat from the interior heater? Yes, this morning even when it was overheating there was cold air blowing out of the vents.

Does it overheat more when driving around slowly or at highway speeds? Both and it tops out all the way past the red area when it overheats, on Tuesday the car completely shut off on me out of nowhere that is how fast it overheated but that was on the expressway doing 75mph.
I am afraid the problems you are having with your Grand Prix are telling me the problem is indeed the head gasket.
The reason I asked about the no heat is because these gases are displacing the coolant and no coolant can flow through the interior heater to give off heat.

It's a fairly big job to have these gaskets replaced.
I do not know if your car is equipped with a supercharger. But you did not mention it so I will give you the labor times on a regular 3.8 liter.

To do both heads, which I would highly recommend after being overheated several times, is close to 12 hours. You would multiply this X the labour rate at a repair shop.
Then you would need to add in the parts required such as a gasket set, possible machine shop charges, coolant and likely an oil and filter change. The parts may add up to 3 to 400 dollars.

Sorry to give you such bad news on a car you really enjoy.
I hope you fix this one or you are able to find another car you will love to drive.

As before, ask me if you would like some more assistance.

Thank you.
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