Coolant escaping overflow tank

[tnstone]

I have a 2000 Pontiac Sunfire 2.2L. It has 203,000 miles. About four weeks ago, I was driving to work when the car started to overheat. I managed to hobble it home. The water pump was out. After replacing the water pump, the temperature ran a little cooler than normal, especially at speeds of 70 mph. After a while it ran normal and then would raise and lower back to normal several times. Two weeks later, it did not lower and started to overheat again. I got out of the car and noticed coolant had escaped the overflow tank. Got it home. Changed the thermostat (we had bought a thermostat and changed it the first time thinking that it was the problem as the water pump was changed just over a year ago. It was the water pump.) We put the old thermostat back on. The car ran at lower than normal operating temperature. Coolant is still escaping the overflow tank two weeks later. The car is now starting to run at normal operating temperature after idling and will quickly climb a little higher when idling. But as soon as I start moving, it lowers again an stays a little cooler.

I just changed the overflow tank cap because I had a hard time screwing it off and on. It felt like it wasn't threaded right. It still feels like the threading isn't right. Maybe it's the thread on the overflow tank itself?

Any suggestions?

[Tech II]

It sounds like you either have a coolant leak, which creates an air pocket, that can create an overheating condition......worse case scenario is, you have a head gasket problem......

Is the electric cooling fan working ok? Turn A/C on and see if fan runs.....

[scott181]

I'm having a similar type problem with the overheating and coolant comming out the overflow. I've changed the thermostat, same thing. What it does is within 30 seconds of startiing it up I get small bubbles in the overflow tank. When they pop you can see smoke, and it smells like exhaust. I have no signs on the exhaust pipe of coolant. No white smoke, no smell of antifreeze, ehaust dust and dirt in tail pipe is the normal brownish dark. Spark plugs look fine. I was told it could be a head gasket or head allowing the exhaust into the cooling system, rather then coolant into the exhaust. Is this possible?? This is a 2000 sunfire with the 2.2L engine. Any suggestions???

[aleekat]

Blown head gasket or cracked cylinder head. You can get a test kit for exhaust gases.

[scott181]

Thanks, came to the same conclusion. I replaced the expansion tank cap and now nothing out the overflow. Ran nice for 20 minutes in the driveway with no overheating at an idle. Drove it less then a mile and temp started climbing fast, got it back home and had lots of white smoke out the exhaust. Got someone wanting to sell me a 1998 sunfire with the 2.4 engine in it that runs great. Will this bolt up in my 2000 with the 2.2??? Gonna be a simple engine swap, or am I gonna run into problems with motor mounts or wiring harness???