Alright, so I have a 2004 Blazer that the heat does not work. After I mess with it it will work for the first couple of miles and then it gradually gets colder and colder. I have replaced the radiator (it had a leak), the thermostat and the heater core. I can hear the blend door switch and I can see the actuator turning the door. I have also had the system flushed 5 times. I have felt the hoses that attach to the heater core and they both feel warm. One does feel warmer than the other. I do not know where to go from here. It has 191k miles on it so i really don't wanna bring it in and pay for someone to fix it as i am also a college student. I am going to try to bleed the system to try to get any air pockets out tomorrow night. Any other suggestions to get the heat to work?

 

Did you use aftermarket parts?
It's been the experience of most everyone that OEM parts give best results.
I would try taking the hoses off the heater core and flush it out with a garden hose both ways, just to be sure nothing has blocked it up. A cooler exit hose suggests blockage.

 

What is happening with you engine temperature during all of this?

George

 

The radiator and thermostat were replaced by a service center. So I do not know. The heater core was from Napa and I replaced that myself since most of the cost is labor.

The temp stays right under 210 but it used to run a little cooler before the heat stopped working. I have wondered if the water pump is going bad but I feel like the temp would get way hotter if that was the case. Does that sound right?

I am kind of new to mechanical work but I am trying to learn.

 

If your engine temps stay within the acceptable range (hot and cold are bad) then you probably have proper water pump and thermostat function. Mine sits at around 190F. If you have a scanner check your engine temp/ECT.

Do you hear gurgling in the dash/heater core? That is a sign of an improperly bled coolant system although this is usually accompanied with overheating. Its possible I supposed to still be getting air through the heater core and not be overheating. If so park the vehicle on an incline, nose up, top off the radiator as the thermostat opens up at high isdle until the level starts to come out of the filler neck and then put the cap on. There is a funnel set up by Lyle on amazon or the parts stores that help you with this by keeping the coolant level above the filler neck.

The hose not being the same temp is usually associated with a blocked heater core. Are you sure that with the two coolant hoses off that you have good flow through the core?

The last thing is your blend door. Your actuator is electric so there is the motor, linkage and the door itself. Are you sure that the blend door has good movement to both endpoint positions and free movement back and forth?

George

 

Here's the Lyle radiator bleeding funnel:


George

 

I am having the same problem with mine. I have the auto climate control and has a mind of its own. in the spring I am going to tear into he dash and replace anything that I can find that it is broken.

 

This is what I'm getting....


I was getting cold air thru vents...temp got over halfway on gauge and them heat started working and temp dropped to about 190....


Recently replaced thermostat cuz I thought it was stuck....


Looks like I'm gonna do above mentioned step.


Thanx!

 

What is weird about mine, is that if I turn the temp **** to cold, then back to hot. The heat will usually start working again.

 

Tajohns , that pretty much sounds like a hung up Blend door issue...

Bagherra's Blazer either has trapped air , or a blockage from the sounds of it...