Heater Core Replacement

Discussion in 'Chevy Trailblazer Forum (GMC Envoy)' started by mb73, Jan 10, 2007.

  1. mb73

    mb73 New Member


    Has anyone had to replace a heater core on a TB/Envoy yet?

    I have a nasty coolant smell and moisture (on the windshield and side glass) coming out of right side defroster and dash vents. There is a fair amount of coolant in the foam insulation for the heater core and A/C lines in the passenger side footwell but no wet carpet.

    The Haynes manual shows a very involved repair including removing the dash, instrument panel and steering wheel(!) and my GMC dealer wants $925 plus tax!

    Do the engineers who design this stuff ever think that someone may actually have to repair it someday?!

    Any feedback would be appreciated and thanks.
  2. ChevyFan

    ChevyFan The Sheriff Staff Member 5+ Years 1000 Posts

    If you've got that a LOT of liquid, then it's the heater core for sure. They always seem to go out in the winter when you're using them a lot.

    Did it break all of a sudden or was it over time slowly? I try to use the alumaseal stuff, that I know ... you're not supposed to use anymore ... but it's worked for me time and time again as a temp fix that even has lasted 6 months.
  3. ChevyFan

    ChevyFan The Sheriff Staff Member 5+ Years 1000 Posts

  4. mb73

    mb73 New Member

    Thanks Steve. You're not the first to suggest this fix and I'll probably try it.

    Still I'm concerned that I have a puddle of coolant collecting either in the heater ducts or under the carpet.

    BTW, I noticed the nasty odor late summer. Wasn't sure what it was until I noticed the interior glass fogging up when it got cooler in the fall and put two and two together.
  5. unplugged

    unplugged Epic Member 5+ Years 1000 Posts

    Yes, there are evil engineers and they even have a website: Evil Engineering My imagination runs with a thought that they have Evil Engineering gatherings where they swap stories about the poorly engineered crap that they have spawned and unleashed onto the public.

    I helped a friend with a heater core swap on his 65 mustang. After looking at disassembling the dash he decided to take the sawsall to the heater box at the firewall. It certainly was eaiser, but all these years later it seems like a shame to have butchered such a nice car.

    PS Anyone who engineers a car so that it costs nearly a grand to swap out the heater core should be taken out an shot. :twisted: :twisted: :twisted:

    Good luck on that project. Let us know how it turns out.
  6. ChevyFan

    ChevyFan The Sheriff Staff Member 5+ Years 1000 Posts

    RE: Re: Heater Core Replacement

    In an earlier life I had an '82 mustang in which the heater core popped and scalding hot water rushed onto my feet and legs. Fortunately, I was going to work and was wearing heavy leather boots at the time or I would have had 3rd degree burns on my feet. It was HOT. I got to work and had to route the heater core lines together, I seem to remember it was like 25F too and snowing, not a fun day.

    Anyhow, if you try the alumaseal first, let me know. Otherwise, post about the heater core swap.
  7. GaryL

    GaryL Epic Member 5+ Years ROTM Winner 1000 Posts Platinum Contributor

    I had to replace one in my brother-in-law's furd truck a couple of years ago. Had to remove the dash to get to it. My neighbor had done one just like it a couple of months earlier and said it took him and a friend 8-9 hours. I did it by myself in about 4 hours. If you can find a step by step guide, it might not be as bad as you think.
  8. unplugged

    unplugged Epic Member 5+ Years 1000 Posts

    I had my Silverado in the shop this morning for 55k service and we were swapping stories and when I mentioned heater core r&r he said that the book quotes 8.5 hours for a Ford Taurus heater core, but that it takes 10hrs! :shock: :shock:
  9. 84fiero123

    84fiero123 Epic Member 5+ Years 1000 Posts Platinum Contributor

    Had a 77 LTD II the heater core went on me, start to finish 5 min. and all under the hood.

    Why they didn’t keep doing it is beyond me, why no one else did it that way is also beyond me.

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