2001 Pontiac Montana head gasket or intake manifold gasket?

I have a 2001 Pontiac Montana that was overheating. It was low on coolant, and using coolant. I took it to a mechanic who checked it out and found exhaust gases in the coolant. He initially told me that it was a bad head gasket. After doing a bit of research, I am told that it could also be an intake manifold gasket. I know I am losing coolant, but I cannot tell where. I don’t think it is going into the oil, as my oil level does not go up. I do not see coolant leaking below the vehicle, so perhaps it is going into the exhaust? Or leaking slowly on top of the engine where it is burned off before it can go on the ground.

Is there any test I can do to determine which gasket is bad before tearing into the vehicle? I thought about sending an oil sample off to determine if I am getting any coolant in the oil, but I don’t know if that would be useful information at this point.

Coolant will NOT simply evaporate by sitting on the engine itself. SO if you are losing coolant…you are more than likely burning it. Do you see Puffy white clouds of smoke/steam out the tailpipe? If your engine is fully warmed up…you should NEVER see steamy “smoke” out the tailpipe. its really steam not smoke…

Another symptom is that your radiator hoses will seem over pressurized if your head gasket went bad…gaskets go bad in many different ways…and I am describing a cylinder pressure leak into the water jacket type of failure…cylinder pressure will leak into the coolant system and over pressurize the radiator…then leak back into the cylinder and be burned.

You can either take of the head and repair this properly/mechanically…or pour a bottle of Blue Devil into the system and drive on… Follow the directions to the letter on the blue devil however.

As a mechanic I would just repair it …but Blue Devil works 9 out of 10 times…up to you One solution is 60 bucks…the other is probably near or over 1000 because you have a V6 you have TWO head gaskets…so unless you have a GOOD mechanic to determine which head is the culprit most mechanics replace both

Sorry for the cheery news…but thems the breaks…


It’s a bad head gasket. A leaking intake manifold gasket wouldn’t cause exhaust gasses to enter the coolant.



bring the car to a shop that deals primarily with GM vehicles. Bring it to a Chevy dealer, better yet.

Your car has the 3.4 liter V6. The 3.1 and the 3.4 are well known for having intake issues.

This is not the latest TSB, by the way.

Check this out also. This will give you an idea of what the repair entails. A competent mechanic could have you back on the road without breaking the bank.


Yesterday, I was under the van looking at suspension parts, and noticed a trickle of coolant dribbling down the firewall. It was dripping onto the exhaust and burning off. I then double checked the head gasket chemical test. It came back good three times! Apparently the mechanic was either lying, or sloppy and let some coolant boil into the tester and “look” yellow.

Investigation revealed that the two hoses that go into the heater core had failed at the quick connect, and they were leaking. Head gasket not the problem, I need $30 for hoses.

I am a bit annoyed that the original mechanic got it wrong. And that I took so long to double check his diagnosis.


I’m glad to hear that you don’t need an expensive repair after all.

And thanks for keeping us updated!

It turned out to be a very slow leak, and very hard to find. Hope it helps someone.

@dockrat100 after replacing the hoses, keep an eye on the temperature for awhile

I always keep an eye on the temperature, but what would cause a problem after replacing the two hoses?

@dockrat100 What if the leaky hoses weren’t the only reason the car overheated?