My 1992 Camaro RS (305 5.0L) has had a strange temperature fluctuation the past couple times I've driven it. I'm not a mechanic, but I do know a little here and there so I'll try my best to tell what's going on so I can get some ideas on what I need to do.

The car doesn't overheat, or even come close. The temperature gauge will go between halfway at 12 o'clock and the first mark from cold. It normally runs just over halfway between the two, and I've attached a photo of where it normally runs. I know approximately when the thermostat opens on my drive home, and it's like it is doing this multiple times. I only notice it at highway speeds, when I am going 60-80 mph. Once I'm in the city, it doesn't do it.

I've only noticed this happen at night, when it's been below 40° F. It hasn't done it during the day when it's been above 60°F.

The radiator fan is wired into the fuse box, and runs constantly from the previous owner. He didn't like how hot the motor ran and couldn't get the wiring down right to have it cut on when he liked. The thermostat is newer.

I don't know if this is related or not, but the overflow does lose coolant from time to time. It isn't a steady loss, it's about half the range between the hot and cold fill, and it's all at once. There aren't any leaks, and the radiator is topped off when cold. The motor runs fine, and I haven't been able to smell any coolant burning or find any in the oil or on the dipstick, but I haven't gotten the change the oil yet. I'm not worried about it being a head gasket failure.

I still talk frequently with the previous owner and he suggested first letting the car warm up with the radiator cap off to see if the coolant in the radiator drops when the thermostat opens, and in that case the radiator itself would be low while the overflow isn't.

Any input would be appreciated. I've got a few people telling me it may be the fan making the motor run cold, but I'm not very sold on that idea as it's like the thermostat is opening and closing multiple times.

 

Couple thoughts


1. The temp gauge in GMs especially of that era fluctuate a lot. In the city it'l lprobaly stay at a higher temp cause you're not getting highway air flow to help cool it.

2. Ive had many cars where....the coolant would seem to mysteriously drop etc... I kinda thin its just evaporation. the amount in the bottle isn;t really a lot..it just seems like a lot cause the tanks shape. It could just be the water part of the coolant evaporating? thats just a theory though.

3. The fan....honestly, its probably making the car run a bit too cold if its running al lthe time....... not to the point where its detrimental...but cold enough where it might be affecting the car's peak efficiency...... also, the motor probably won;t last too long?


Mine used to do that too... I fixed it though. Id rather have the fan cycle on / off personally. Why not just install a lower rated fan switch? Fro mmy research here, the fans were set to come on at a pretty high temp for emissions reasons or something.... but there are lower temp fan switches available.