Hello everyone I just purchsed a 05 lly duramax cc sb 4x4 for 7650 out the door. I didnt notice it but the heater is not working. the temp only goes up to the second line above the 160 temp so it should heat up enough to work. People i talked to already say change the thermostats but i just wanted to get someones opinion on here to.

Im totally excited to have a diesel wanted one for a long time just sucks to automatically start doing work on it

 

Update: I changed the thermostat today and the engine temp rose to the right level but still no heat. Please help

 

You could have an air pocket in the system. Have you tried to let it warm up with the radiator cap off and blast the heat in the cab?

See if the anti-freeze level drops. If it does top it off. You could also try to take the radiator hoses off of the heatercore and flush the heatercore out with a garden hose. Work the hose back and forth between the two pipes to flush any debris out.

Tony

 

Did you open the bleeder screw on top of the thermostat housing before you filled coolant? Probably just an air lock. You can try opening that bleeder screw with engine not running and see if you are getting coolant flowing out. You might have to disconnect a line at the heater core to help get the air out.