2001 Blazer LT, 4x4, V-6, 124,000 miles. I have noticed in the past two days that my engine for a brief moment will overheat on the way to work. I live roughly 8 miles away. Initially the engine seems to warm up and everything is fine. But there is a point that (usually within mile or so of work) the heat goes cool, the engine temp almost pegs and the Check Gauges light comes on. I then turn on the defrost, crank the temp all the way over, and turn up the fan to max. It drops off realitively quick and then runs normally. I replaced the thermostat back in February but I am wondering if that is not the problem. I am assuming that the initial heat is from the trapped coolant and the thermostat has not opened yet. Then when it "sticks" (?) it over heats, and then it suddenly opens up. Any ideas????
I don't have a problem replacing it again, just wanted to know what you fine folks thought. Thanks.

 

Definitely sounds like you have air in the system. I would do a cooling system service just to be sure that everything is ok in there.

A new thermostat & Stant safety radiator cap along with two gallons of Zerex extended life coolant (my opinion, but Peak and Prestone are good as well) and about 6 gallons of distilled water. Use the distilled water to flush the tap water out of the block, radiator, heater core after you have gotten everything cleaned out with the garden hose and to mix 50/50 with the coolant.

It would also be a good time to thoroughly check over your radiator hoses.

 

I just realized that I forgot to mention I had the radiator replaced as well within the past couple of months. Perhaps that is where the air has come from. My mechanic said he filled it after the replacement and I checked it every day and topped it off as need be. Perhaps we didn't get it completely topped off. I have not seen any coolant on the ground so I assume my hoses are ok. I will look them over today during my lunch break.

 

You might want to get the lines flushed too. There could be sludge or a clump of something circling around in the system that a flush would clear out.
Definitely do a coolant change though and see how that works..

 

I found the source of the air in the system. As much as I hate to admit it, I "thought" the system was full. I went out at lunch, popped the hood, and the radiator cap. Guess what? It was really, really low. There is my air pocket. There are no leaks and the hoses are fine. I filled it up with some anti freeze and I will check it every morning for a while to ensure it stays there. I knew it took time to initially completely fill it after the radiator replacement, I just got lazy and didn't for a while. What a putz.. . . . . .

 

haha it's always the simplest things. Did you bleed the line after topping it up? to make sure there is in fact no air in it?

 

No but I will. What is the best way to bleed it?

 

The best way to get all of the air out is to pull a vacuum on the system. But that is not something everyone has access to...

 

That's me. I don't have the equipment to do that. Plus it doesn't help I live in a town house and have no garage. I guess the best thing I can do is to continually check it for a while and make sure the radiator is completely full.

 

Just an update: yesterday after filling up the radiator, drove to work this morning and guess what? Everything is fine. No overheat, no CHECK GAGES light. We are happy that the Blazer is happy (again). Going to watch the radiator until I know for a fact the system is completely full. Thanks for the insight.