I am trying to work on my room mates Camaro and I am lost. It is a 1996 V6. When sitting still the car will seem to stay cool on the temperature for a good 10 minutes and then spike to 260 very quickly. The fan will kick on when this happens.
He did not have may heat coming out. Well only very sporadicaly. Here's the part I am stumped on.
When he is driving it, it will overheat also, but less quickly. If the heater control is in the defrost or one of the positions where it might kick on the compressor, it takes longer to overheat. When it does start to overheat, he can change the settings say from defrost position to one of the other positions and then the car will quickly cool down. But he may have to change it to a couple before this happens. And sometimes, rarely, it will blow heat.
Coolant levels are fine. I replaced the thermostat tonight. I did not test the old one or new one. So that may be a bad assumption on my part.
I guess I am thrown by how it is sporadic and the changing of the heater positions. It is like by switching the positions on the heater it is electronically kicking something on.

Any help is appreciated. I know just enough about cars to be dangerous to give you an idea of my repair knowledge. And it is was -12 here today and it still overheated.

Did it really overheat, or is the gage not functioning properly? Could be the temp sensor!

There are probably bleeders in the cooling system as the radiator may sit lower than the coolant level in the engine. See if you can find them (if it has them, as I am unfamiliar with these cars) and crack them open starting with the lowest one and bleed any air out of them. Continue bleeding them until you have nothing but coolant coming out of them. Be sure to refill the coolant if you get allot of air out of any of them. Maybe that will help.

Yes it is overheating. I could hear the boiling going on.

I will see about bleeding it today.

I appreciate all suggestions. As I said, I know just enough to be dangerous and can usually reason my way through troubleshooting. But since I have never worked on one of these before, I am trying to learn as quickly as possible. Even if someone can tell me what it most likely "isn't" that will help me on where I spend my most time troubleshooting.

Thanks!

Make sure there is sufficient coolant in the system. I know this may sound stupid, but if it has a small leak, he may not have noticed it and it would have eventually emptied the system. Just something to look at.

Well I feel like an idiot. I learned a lesson today. Never trust the overflow tank for telling you the radiator is full. Everything "appeared" to be fine by the levels in it. Wrong! 2/3 of a gallon later, the radiator was filled. We have driven it twice on short drives and checked it and it appears all the bubbles are out of it. But he is going to keep another half gallon with him and check it daily to see what it looks like. I do know it is going to need flushed soon. And that may still be part of the problem. But I am going to make sure the levels stay up first in case there is a leak I haven't found.

This is the first time I have ever posted on these forums. I want to thank everyone for their advice.

And yeah, I have to figure out why the overflow tank shows one thing and the radiator another. But I guess one thing at a time. LOL

Congrats on finding the problem.