I just got done switching out the heater core in my 2002 Blazer ZR2, and am now trying to finish up and fill the coolant. I can't seem to get more than a gallon or maybe gallon and a half in. I tried starting it to try and get it to start circulating through the engine, but the temp came up high (~240 F) within 2 minutes or so and I had to shut it off. Also, there is no sign of heat but I sort of expect that since it doesn't seem to really be circulating anything. What could be the cause? I'm stumped as to why it won't take it?

Thanks!

 

Did you flush the coolant system? Sounds like a circulation issue...

 

try flushing the heater core

its worth a try

 

Vapor-lock in the heater? Try loosening the heater return hose, then running the engine until coolant flows from the hose.

 

Thanks for the input guys. I ended up pulling the return line off the heater core and connected the hose to the flush out fitting on the inlet to bleed the new core. I also parked the front end up the bank in front of my house to get the rad up as the highest point and this got tons of air out. I could hear the gurgling sound in the truck. All seems good now.