Hey everyone, I've searched and did my best to try to receive hot heat out of my vents. My blazer seems to be picky at times when it wants to throw me warm air and then cold air? For example if my blazer is idling, it would throw me warm air, but once I hit the freeway hot air starts to blow in and then turns into warm air. At this point I'm completely clueless. I changed the thermostat, all coolant is topped filled, and I flushed the heater core as well. And the two hoses from the engine bay that connect to the heater core are both warm/hot together with the same temperature. But when I flushed the heater core, little debris came out and I had no access to a hose or air compressor. What I did was connect alittle tube that fit perfect on the outlet and I got water to go in there but I wasn't able to pour water to the inlet. I thought since the water came out clean right away it must of did the job, so I'm going to try to flush it again. But the weather here in CT has been in the low 30s so I really have no access to a water hose outside. Any thoughts? I'm cold lol

 

Bump! Any help or advice please!

 

Jack up front pass. side. Open radiator cap. Start and let it run, most likely coolant will go down. Add coolant, let it continue to run and add as needed. When it finally stops taking coolant button it up and see how the heat works. You will need to run it long enough for the thermostat to open and close a few times.

 

did that already, I idled the blazer for 20-30mins and made sure I topped off all coolant. Still no change.

 

The key is to have the front end in the air as high as you can get it with the passenger side slightly higher than the driver side. You also have to put it through a few heat cycles as in letting it heat up, then cool off a few times until there no longer are any big swings in the fluid level in the radiator.

 

There must be air in the cooling system and the suggestions above are to burp the cooling system.
I am still in the process of getting the air out in my '02 Blazer after leaving one heater hose clamp off which resulted in pumping most of the coolant out.

I am quite amazed at how much air is trapped; I have filled the radiator to the top, added coolant to the reservoir and then go for a drive; come back and check....coolant low....have done this three times now.

Just to give you an idea that it takes several heat cycles to remove the air. Keep after it and you should get nice hot air.....unless the heater core is mostly blocked....and that is a whole new story.

Good Luck

 

You may also have a blend door actuator issue but as others stated, make sure you don't have air in the system first.

 

Ok guys, I checked the coolant level everything is filled to the top. I went to touch the hoses that goes to the heater core and now the inlet hose is cold and the passenger side inlet is hot? What do you guys think?

 

Heater core is definetly clogged, pull both hoses off and flush out with a garden hose.

 

what sucks is that the hose is frozen under snow right now lol. I'll try tomorrow to run water through again, but any other suggestions? From the two coolant hoses plugged to the heater for with one cold and hot, does that say the heater core is plugged to you?