Been having some crazy problems with the cooling system on a 95 with an LT1, completely stock as far as I know. I ran over something in the road that bounced up and hit the car. It was dark and I didn't see it until it was too late. I don't know if hitting this mystery object has anything at all to do with the problem:

About a mile before getting home the low coolant light came on. The temperature was normal. I checked the next day and the coolant was fine but I topped it off and bled the valves anyway. Turned it on and let it idle for at least 20 minutes, no coolant light. Took it for a drive, about 5 minutes later the low coolant light came on. I turned it around and drove back home. The temperature gauge seemed a tad high, but nothing to worry about. I parked the car, let it cool, and again checked the coolant, bled the valves, and turned it on. It idled for about 20 minutes with no light. Took it for a drive and about 2 minutes later the coolant light came back on. I turned it right back around and drove home, but by the time I got back the temperature had DEFINITELY shot up, close to red. There was purged coolant all over the engine compartment.

I was moving back to school so I just had it towed to the mechanic's. They said the coolant levels were fine and they couldn't find a problem. The light did come on, but then it went back out (by itself, the mechanics did not clear it). My dad picked it up and drove it home (about 10 miles). No coolant light and no overheat. Since then the car has been sitting at home waiting for me. It was turned on once and left idling for about half an hour.

I went home recently and looked at the car. After about half an hour of idling the light came back on. The temp was a bit high, but that could have been from idling for so long.. I hadn't driven it so I just turned the engine off.

I'd suspect it's just a coolant sensor or something, but that one overheat scares me. The car was driven since then with no overheat, so I wonder if it's possible that I just didn't bleed the valves completely and the mechanics took care of it. Any ideas what could be going on? Is it possible that the thermostat is acting up or something else is wrong?

 

Try a new radiator cap. May sound silly, but it can cause overheating.
If low coolant light is going on but car is not overheating, make sure level in the radiator, not just the overflow tank, is high enough to keep the sensor from triggering.

 

Are the fans working?

 

Yup, the radiator was what I checked both times. Coolant was full there. And the dreaded LT1 fans... the fans work, but I don't remember them turning on at any time during all of this. I don't think that was a problem though. I'm probably just going to have them completely flush the cooling system and replace the low coolant sensor. Then I'll go down for Thanksgiving and drive her around for a day, see if the temperature rises abnormally again.