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6.0 heater not so hot

Discussion in 'Trucks and Trailers' started by SiteSolutions, Oct 11, 2007.

  1. SiteSolutions

    SiteSolutions LawnSite Bronze Member
    Posts: 1,114

    Anybody heard of this? Ever since it's dipped into the 50's in the mornings, I've tried to use my heater. I let the truck warm up in the driveway before heading out, but even after several miles of driving, the heater will only blow warm air for a minute before the air turns cool. Yesterday, I was pulling a moderate load for an hour and the heater still wouldn't stay hot. Do I need to get a winterfront for this thing or is there a problem I need to see a mechanic about?:confused:

    CLARK LAWN LawnSite Silver Member
    Posts: 2,526

    what does the temp. gauge read? if it stays low you may have a bad t-stat. I have never used a winter front on anything till it was down below 20 degrees.
  3. topsites

    topsites LawnSite Fanatic
    Posts: 21,653

    Yup, sounds like you're either low on antifreeze or your thermostat is stuck open, I'd check the antifreeze first thing in the morning when the engine is cold, more than likely it just needs some 50/50.
  4. SiteSolutions

    SiteSolutions LawnSite Bronze Member
    Posts: 1,114

    Antifreeze was my first thought but that checks out fine. Temp gauge reads normal, in the middle, when this happens.

    The heater core is warm and air flows through it when I first turn on the heater, but then...

    either 1) there is only a trickle of coolant going through the heater core
    or 2) the door that routes air through the heater core moves back

    because after 30 seconds or so, the warmth starts leaving the air and then it is like barely warmed outside air.

    A guy I know said it is the air mixing door, that it is behind the dash and takes 6 hours to fix, plus about $175 in parts. Another guy said it could be a little doo dad that routes the coolant out of the block to the heater core, which is a lot cheaper and quicker fix. I haven't crawled up in the engine to look; it's a jungle in there.
  5. stroker51

    stroker51 LawnSite Senior Member
    Posts: 819

    My 96 had a similar condition last winter, only my warm air was much more fleeting, only a few seconds. But it wound up being a pencil had fallen through my defrost vent and jammed in the blend door. hope it's something simple like that.
  6. xcopterdoc

    xcopterdoc LawnSite Senior Member
    Posts: 752

    I would guess a blend door problem.
  7. SiteSolutions

    SiteSolutions LawnSite Bronze Member
    Posts: 1,114

    I'm not convinced on the blend door, although that seems just as possible as the other thing. I need to let someone with specific experience try this out, but here's what I did:

    I turned all the noisy accessories (like sports talk radio) off and turned the blower all the way up. Then I listened while turning the knob from cold to hot. The noise changes when I turn it to hot. The air gets warm for 20 or so seconds, then goes cool (but not ice cold)... I listened specifically to hear if the noise changed while the air temp changed but it didn't. This would have been an easy indication that the blend door wasn't staying switched over, if the noise from the air ducts changed gradually with the air temp. But it didn't, so I am not sure it's the blend door. The noise from the ducts changed directly with the hot/cold knob, and never changed on it's own. "Cold" setting was always colder, noisier, and less muffled; "Hot" setting was always warmer, quieter, and more muffled. Might have been flowing slightly less air but hard to tell without a tool to measure that.

    It's possible that the blend door is getting jammed part way over, and the hot air sitting right behind it is quickly blown out by the cold air? So maybe it is still the blend door, but instead of a weak door that moves all the way and then eases back, it just isn't moving far enough in the first place? Sure wish I could see up in there but by all accounts it takes three hours of dash disassembly to get a look at this thing.

    I'm sure the coolant lines are just as much fun to access.

    Either way, I will probably just wear a jacket and live with it for now. It's not like I live in Minnessota or something. Maybe when I get the 60,000 mile service I can have someone look at it.
  8. 04superduty

    04superduty LawnSite Member
    Posts: 60

    vaccum leak slowly letting the blend door slowly move, or the valve on the heater hose is not working right.
  9. xcopterdoc

    xcopterdoc LawnSite Senior Member
    Posts: 752

    Remove all pain.. open check book.... go to dealer, they have all seen this many times before. It wil be fixed and you will have heat and ac.
  10. mike lane lawn care

    mike lane lawn care LawnSite Bronze Member
    Posts: 1,707

    ya know, in the 50's here i still drive with the windows down. man up

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