Alero overheating only in special circumstances
 

So this summer I was having a leak which turned out to be my Lower Intake Manifold gasket. Also replaced the front head gasket. The thermostat and temperature sensor are new as well and I also took out the old coolant and put in new stuff. There's no more leak now, and the temperature holds steady, but there are two problems:

1. Instead of the temp gauge's normal position being just below the middle mark, it is now consistently at the middle mark.

2. If I'm driving and stop for only a short period of time, such as to get gas or run into a store, when I start driving the car again the gauge starts creeping up towards the three quarter mark. I shut the car off before it gets much higher than that, but I have no idea why it's happening. Could it be that the cooling system needs to be bled? If so, how does one do that exactly? I know where the bleeder screw is, but what is the procedure?

I had my intake gaskets done in the spring and am experiencing the same symptoms. I've tried bleeding my system multiple times but it hasn't fixed it. I'm here for suggestions too...

the bleeder on the 3.4 is on the left above the water pump it has two fitting on it. The smaller one is the one you loosen. Then tighten it back up. Repeat a few times. Low on coolant? Thermostat faulty? Leak somewhere else? That's all I can think off. Hope it helps!

the gauge is really pore way to determine the coolant temp. example such as my truck runs solid at 188. the gauge shows 210. you have installed a thermostat and that alone can effect how hot your engine is. you really need to get your hands on a tool that will plug in to the DLC and see what the ecm is actually reading.

now when you drive, then shut your car off, all the heat builds up. your coolant temp will actually get higher because the coolant is no longer circulating and no longer being efficient at heat exchanging. which results in a hotter engine after shutting it off for a brief period.

now typically your engine will get hotter then your average hot temp before the thermostat opens. then should maintain a good temp thereafter.

now i do agree your gauge seems high, but wihtout knowing what the ecm is reading, it could be anyone's real guess.

IMO

Yeah, I also had the same problem going on with me. There must be a small leak in an area we aren't checking. I replaced the thermostat and everything, the problem happens about once a year for about a month.

So far, I have found the only solution to be (and I know, I hate this stuff too) Bars Leak. Just as a last attempt I poured some in and it hasnt overheated since! *Knock on wood*

Overheating
 

A lack of pressure can cause overheating, and if it stopped when you put in the bars leak, my first guess would be a pinhole in the radiator or side tanks. Like someone stated above, if the coolant is not circulating properly, it will actually heat up, and lower pressure in the system from a leak can be an issue. Also check to make sure both your fans are coming on at the right times, there is a high and low speed relay for each I believe.

Thermostat or coolant sensor? check those.

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