Hi my 1995 lumina overheats when in low speed traffic and the gauge seems to stay in place when at a total stop, like if the gauge is more than half-way over and I'm at a total stop the gauge will just sit there.. The only way the gauge goes back down is when driving at high speed.. what could it be? I have made it so the cooling fans under the hood are on consistantly, it still has the same problem, I took it to a local mobil shop and they said it seems to be bleeding out the air and you can see bubbles in the coolant tank. They said it might be a head gasket, I really hope it isn't, has anyone else had this problem? and if it is a head gasket is there any way to find out 100% sure without taking the whole engine apart?