Hi! I have a 98 Blazer and just a few days ago I noticed my check gauges light come on and my temperature needle was in the red zone. I pulled over and felt my car, no excess heat emanating from it. Called my dad and had him put more coolant in, but before he made it to me, I started the car back up and drove around and it cooled down on it's own and went back down to the middle where the needle usually is. He added the coolant anyway to be safe, and I didn't have an issue with it again until a few hours later. I didn't use my car the next two days, but I used it again today and it immediately kept fluctuating between the 1/2 mark and 3/4 mark, and eventually went into the red zone again for a few minutes but went back down to the 3/4 mark. Once again, no heat coming from the hood, or any smells. My radiator recently went and was replaced and a new thermostat was put in with it. Any ideas? Is it safe for me to drive with it like this? It feels like it's running fine, but watching the gauge sneak up into that overheating area really stresses me out!

EDIT: Also, while the gauge reads a higher temperature than normal, my hot air will come out cool sometimes but goes back to warm eventually.. but not as hot as I know it can get, just a moderate warm temp.

 

Sounds like you have air in your cooling system, that will cause the fluctuating temperature. And you wont feel really any more heat coming from the engine bay when it over heats like that, you would have to have a thermal heat gun to check the pipe that feeds in above the thermostat if you wanted to check that way.

But sounds like you need to burp the system. Jack the front of the truck in the air as high as you can get it with the passenger side higher than the drivers side (one notch on the jack stand) then with the engine COLD take the cap off and start the truck and let it get up to temperature, adding coolant as needed.

 

Thank you, will try that as soon as soon as I can have my dad over to look at it. In the meantime, is it dangerous to drive the car in that condition? I live about 30 minutes from where I work, and I'm nervous to try driving it that far

 

Yes, it can be dangerous to drive the car with air pockets in the cooling system. It can cause the thermostat to take longer to open (if the air pocket is at the thermostat) which will cause the truck to run hot. I would try to burp the system where it is, just throw a jack under it and jack it up, then follow 97cherryblazer's instructions.

 

You have to switch the heat controls from window defrost to foot heat then vent heat also.. it opens all the tubes between each and helps purge the air in the lines.