Pontiac Repair: coolant surge tank overflowing, coolant water, engine gaskets

Question
i have a 1999 grand am gt, 3.4 L engine, auto trans. there are no leaks coming from the engine gaskets.Coolant is at proper levels. Today, there was some coolant on my garage floor. Investigation showed some coolant coming from the coolant surge tank resevior hose. Surge Tank cap is brand new. I had the lower intake gasket. water pump & t-stat replaced on 3-17-2005. No leaks from that area. Any ideas on what might be causing this? Thanks in advance. Phil S.

Answer
Hey Phil:

Why was the cap replaced? Is it an original equipment part? If not it can be the cap it's self is bad or not sealing to the tank properly. A flot of after market parts out there are JUNK. The level in the tank can be to high when the engine is cold and when the car heats up the coolant/water in the engine expands and if it expands more that what the tank can hold it will push it out past the cap. If the engine is running to hot it will expanded it even more and the same thing can happen. There can be something wrong with the sealing surface of the tank and the cap may not be able to seal properly. Those are the only reason I have for you Hope it's one of them. Good luck :}