First post in a while, Blazer has been good to me not giving me any problems until now. I am having a random over heat, it will happen 3-4 times a week. First i will have the heat go, blowing cold air, then i notice my temp needle going up and up to about 230* - 250* range. I replaced the radiator a year and a half ago. When i changed it i did a flush and switched over to green coolant. What could this be? Thermostat failing? Water pump failing? Please helppppppp!!!!

p.s. I like the forums now they look pretty GOOD! I don't like how the search shows the newest post instead of relevance.

 

Sounds like air trapped in the coolant system. Raise the front end slightly with the right (passenger) side slightly higher; loosen the radiator cap and let the engine run to operating temperature, adding coolant as necessary. Let the engine cool down and repeat the procedure. Let us know if it helps.

 

I would also put in a new thermostat just to eliminate it as a suspect. It could be failing and not opening all the way. Don't buy the $2 house special either... go for the $10 name brand one.
If it only gets hot when driving very slow or stopped then check your fan clutch.

 

@rriddle3 I believe all air is out I replaced rad a year and a half ago and burped the system, but will check in the morning.

@bandidolenny how do you check the fan clutch? It started to get hot today when I was stopped by a train.

 

When the truck is hot and idling, pop the hood and watch the fan while someone cuts the engine off. If the fan does not immediately stop then replace the fan clutch. The parts store will probably ask you what your gear ratio is for the fan clutch application.

 

ok so i changed my thermostat yesterday and added about a gallon of coolant/water to the system....I'm thinking i might have a bigger problem here! Gonna have to keep an eye on the levels. but other than that it's running @ 195* nothing over!!!

 

Good deal! Let us know if anything changes.

 

To give you a definite answer, get your cooling system pressure checked. You probably have a leaking head gasket. Pull your oil cap off and if there is some milky substance on it then there you go. Do a search for head gasket replacement. I have to fill up the radiator every few weeks or it will start overheating. I am just trying to find a good saturday to tear my engine apart and replace the gasket and clean out the cooling system. I am switching to green coolant after that.

 

When you look at your coolant, is it a solid green, or is there some discoloration to it?