Is the heater core made from aluminum?

 

yes it is.

 

That's what I thought. I was wanting to run some cleaner for our heat exchangers here at work thru it BUT it says on the bottle not to use with aluminum. It quicky ate a hole thru a little bowl I made from aluminum foil which is thinner than the core tubes but still may damage them and make quite a mess.
Gotta get some heat in the cab. New core time I quess.

 

What steps did you take to determine it was a bad core ?

 

Usually the only "bad" heater core is the one that is leaking. If you have low heat I would remove the hoses at the firewall and flush the core.

 

Also, make sure the blend door, temperature switch/cable are working properly...a bad thermostat could be part of the problem too.

 

I have low heat.
I guess I will try this since it's cheaper than buying a core.

Thanks for all the replies.

 

It's not so much buying it, it's getting the old one out and the new one in!

 

yea, i have low heat too ever since my headgasket popped. i know the core doesnt leak, but everytime i start the truck i get a water running/trickling sound in the core as i can hear it moving thru the tubes. and i can't even get luke warm air out of the vents now

 

I swapped the T-stat, no help. One day while driving down the road obsessing on what the problem could be I turned the blower selector thing to the recirculation setting. After about 10 minutes, the heat nearly drove me out of the cab. I returned it to the regular, non-recirc setting, and now it works fine.

does anyone have any idea why this worked?

 

My 97 has the same problem, not a whole lot of fun right now with the temperature around zero. I flushed the heater core and it had little to no effect on the temp. I am gonna give what 54larrry said a try and see what it does.

 

Check your inlet and outlet hoses on the heater core in the engine compartment...if both are hot and the same temperature, the core is ok...the problem is in the dash...blend door stuck closed...servo motor not working...vacuum line off somewhere. Good luck...

 

sounds like a blend door problem since the recirc setting cuts off the outside air.

 

Why setting it to recirc would have cured the whole problem. I am glad it works now, but I hate the idea that I do not understand how that could have fixed it.

 

fixed the problem today on my 02...under the heater core/ac assembly there is a small electric motor assembly with a 3-wire plug going to it. its on the left side of the heater box right up agaisnt the tranny hump near the center of the truck. if you look with a flashlight you can see in the gap between this black motor assembly and the heater box itself...there is a grey bushing. when you turn the heater temperature back and forth you should see this grey piece move. mine was not. a few good turns with some pliers to free it up and now the blend door is able to open and close fully when switching the temperature.

this may or may not be your problem but its a thought.