Pontiac Repair: grandam overheating, manifold gaskets, head gasket

Question
Our daughters '97 grand am overheats intermittently- we have had it pressure checked by a mechanic but they can't find any leaks anywhere- it will overheat and then we add coolant and it runs fine for a month or so and then overheats again. We have not replaced the water pump yet because the mechanic is not sure thats what the problem is and becasue the water pump is so hard to get to. It has 160,000 miles on the engine. We have replaced the coolant fan  Any idea's?

Answer
Hi Shelly:

what engine is in this car? if it's a V6 engine they tend to have intake manifold gaskets leak coolant and it can leak into the engine and you will not see it. Sort of unleikely because they uaually leak out of the engine and onto the ground too. It could have a head gasket leaking coolant into the engei nand it's burning it and you wouldn't see that either. If this is a 4 cylinder engine yes the water pumps leak onto the ground and you probably would smell coolant after the car has been running. These engines also have head gasket issues from time to time but water pumps are more common. To thell you the truth with that many miles anything can be leaking. Good luck :)