My girlfriend's 1997 Grand Prix GT has been running hot on and off all summer long. So I finally decided to try to solve the problem with it. I noticed the intake doesn't have any GM markings on it so I assume its a Dorman replacement. I flushed the coolant, changed the spark plugs (needed a tune up) changed the thermostat with another 195* and bled the air out of the system. Now it runs hotter and overheats quicker than before! Maybe I bought a defective thermostat? I noticed no coolant mixing with the oil or oil in the coolant reservior. A friend who lives 100 miles away said that he feels its either a bad thermostat or a head gasket. I took the car to a garage where they claimed to have tested the coolant for exhaust gases and it came up clean. The service writer said it was overheating due to a leaky coolant elbow? I find it hard to believe that air could enter a pressurized system through the coolant elbow (very small leak) and cause the car to overheat so quickly! The coolant is not low. The car can not be trusted at idle or driving. How to I determine the cause of this? Please help
