My 1996 Lumina temperature gauge runs hot and then cools down within a minute, over and over and over. Supposedly all external problems have been eliminated. Our Chevy Dealer said they need to tear down the engine because the problem is internal. The car runs fine, with no other problems other than the temperature swings.
I have the same problem with my '95 Lumina. After some time of driving the temperature would go up to 3/4. I flushed the radiator, put new coolant and that didn't do anything. Then I put a new temperature sensor and I got all the engine power back. Probably the computer is convinced now that it is actually not overheating . The gage still goes up but comes down again, at least sometimes. Occasionally I also get a Service Engine soon but the Diagnostic System doesn't let me pull any code! Its simply not working. Is the PCM to blame? What can I do?
1) Make sure all excess air is removed from the cooling system. There is a bleeder screw on the water outlet and on the pipe coming out of the pump. I used a vacuum pump to suck all the air out of the lines at the bleeder screws....until the pump started sucking antifreeze.
2) Make sure the electric fans are working properly. If the #1 fan doesn't come or comes on late, the car will over heat. Fan #2 is a backup and only comes on when the engine overheats.
If there is something internally wrong with the engine, it will show up in more than one place. I doubt there is an internal engine problem with just overheating!!!
This is a little late for the original post but may be helpful for someone else.
I had expirienced alot of the same things seen in this post. There is one additional repair step I took.
I ended up taking my radiator out of the vehicle and had it rotted out at a radiator repair center. After reinstalling it and making sure the air was purged from the engine cooling system, the problem went away and has not come back.
This was after replacing several thermostats and a blown head gasket.
1996 Lumina Intermittent Overheating
