Any tips will be appreciated, dont let me die in this canadian winter.

Model: Jimmy 2 door
Make: GMC
Year: 2005
engine/transmission option: 4.3v6/auto with 4x4
are you mechanically inclined/have the right tools?: yes
Issue(s): no heat coming from the vents

heater core issues seem to be common among jimmy/blazers, so far i haven't found my issue, here is wat i have tried.

first off i touched the hoses running to and from the heater core( after engine is at running temp) . 1 coming from the engine head is hot, the one running back to the pump is warm but not as hot as the other one.
so i tough my core might be clogged. i unplugged the hoses and ran a garden hose trough and it flowed perfectly and was very clear, no gunk/debris came out.

second, was checking if my heater selector switch was good and it was.

3rd i checked if the motor that activates the door inside the heater box ( lets air bypas heater or forces it trough the heater core) it runs great

4th while checking the little mortor i could actually fit my hands on the shaft of that heat selector door and it turned freely all the way from full open to fully closed.


so now with half my dash appart, i feel like im back to square 1 as the 2 different hose temperatures from the inlet and outlet of the heater cores seems to be the only thing not right cuz the loss of heat isnt going inside the cab lol.
maybe il try blowing air into the heater core this weekend.

are you full on coolant? what does your coolant temp gauge do? did you flush the core in both directions or just one? check the heater hose that was cold it could be plugged up. dex cool turns into a sludgy gunk over time and you could have some stuck in the heater hose that is cold.

i made the water flow both ways and trough the hoses actually was easier acces then the core itself.

The heat in my 4.8 sucked, and when I googled it ( I did most of the things you mentioned) it was a valve door that allows the coolant through. They get gummed up.
I read your post twice and didn't mention anything about that part.
Yours nay be different? Try Google. I tried

My step-dad had his heater core going out in is Silverado and he ran clr through it and it made it as good as new. But his was plugged and yours doesn't seem to be but it may be worth a shot?

Dumb question most likely but.............you did change the thermostat, right?





This post was edited by said_aouita on Sep 24 2015 04:44pm

figure out which one is the blend door then. its more than likely the one ibot is mentioning its probably not functioning right. when you are moving your switches you should see the different doors opening and closing.

my thermostats works great as far as im concerned i dont have any temperature issues.

like i said the heat selecting switch works great and actuates the motor for the door and goes from completly shut to completely open. but thats only inside the air box. i dont seem to have any valves for the coolant it goes directrly to a water neck on the pump on 1 side and dirrectly into the intake on the other side

just finished working il look into it this wekend.

This post was edited by BlueAndWhite on Sep 25 2015 10:53am