Ok so I've researched this problem and it seems to be pretty common.

I get a little warmth at the beginning, then it cools off to outside air temperature. This afternoon I put a new thermostat it, then I flushed the coolant with one of those prestone flush kits where you put a garden hose on the intake.

Anyway, one line going to the heater core gets hot, the other is slightly warm. Do I have to flush the heater core seperately? Since the thermostat will never open with the garden hose method?

Is there a way to purge air out of the system? Or will the pump shoot it out and take care of it somehow? I can squish the core hoses with my fingers, should there be any pressure on the hoses?

The reservoir and radiator itself are cool to the touch. The block gets nice n hot. The temp hovers around 180... could the thermostat just not be opening yet? I think its a stock 195 degree.

The engine runs at decent low temperature, so that means the water pump is fine right? Maybe my core is clogged, I'm gonna flush it tomorrow morning but if anyone wants to chime in feel free.

 

Both of your heater hoses should be the same temperature. If they're not, it's because the coolant is not flowing through the heater core. You can flush the heater core by itself.
If your coolant is low in the radiator, run the engine with the rad cap off, til the coolant level drops ( that means the thermostat has opened), then top up the rad coolant level and install the cap.

 

Thanks for the reply.

Early this morning I disconnected the heater core, connected one hose to a garden hose, and the other to a drain basin. I used clamps to make a nice pressure tight connection and cranked the garden hose up. Some awful gunk shot out of it then th water went clear. I made sure to swith the hoses and flush the other way, and sure enough more nasty stuff came out. I hooked it all back up and now we got some heat!

 

Good job! IT should self purge.

 

Good job man! Glad it was as easy as a simple flush!

 

hey guys im tony. I have a 97 Blazer 4x4 and a 97 z28. I just replaced the tstat in the truck and its still blowing cold air.
I havent had the coolant flushed in a few years but its my winter vehicle/DD the coolant is a dark orange looking color. Its full im just not sure if i should flush it again or what todo? I have a child so he needs to be warm in the winter.

 

The system should be flushed every 2 years or 24,000 miles, so if its been a little bit that would be the first thing that I would do.

 

thanks for the responce, if flushin out the heater core doesnt work, I guess thats what ill have to do.

 

Had same problem, Flushed heater core this morning and very little amounts of debris came out, however heat works wonderfully now. Also changed tstat since the motor was taking forever to warm up. now warms up quicker and heat works.