My 99 blazer keeps overheating and the check engine light keeps coming on. We replaced the thermostat and its still doing it. any suggestions on what it may be?

 

Could be air ithe lines or possibly bad thermostat or installed upsiede down. You can get bad ones new. Could also be a plugged radiator

 

I'll check it out thanks

 

Could be different things but a blown head gasket or cracked head (cracked head is doubtful with iron heads) putting pockets of combustion gas into the cooling system comes to mind. Pockets of combustion gas do not cool very well at all. Is the engine blowing white smoke when hot? This happens when coolant gets into the combustion chamber with the hot engine running. Can you keep water in the cooling system for any length of time if you fill it up completely and start it with the radiator cap off, or does it start coming back out right away?

As a last resort test you can cool the motor off completely, take the thermostat out, take off the water pump belt, fill it up so water stays level with the thermostat flange for some time, start it up, and watch for bubbles during the first 60 seconds of running.

Good luck