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2001 Chevy Tahoe, no heat...blows lukewarm...

Discussion in 'General Chevy & GM Tech Questions' started by lowpost, Jan 31, 2012.

  1. lowpost

    lowpost New Member

    Heat worked fine 12/19-27th. As of 12/28 I am blowing barely lukewarm air to all vents on all speeds. Blower comes on/off as directed and blows hard. I can't seem to get any real heat however.

    I also must note we've had an old issue we lived with for around 6 years now of not being able to adjust the temperature while driving, only can choose before starting the truck, your start and that's the temperature you get for that trip. Wanna turn the heat down? Gotta stop, change the dial and restart. Even this began to fail in the last 12-14 months. I really think this could be the blend door which has finally just stopped getting over to the warm side and is stuck on the cool side.


    I am NOT A MECHANIC! I'm a nut-turner as they say...know my way around a fair amount, been using tear-down manuals for years to maintenance my cars/trucks. I've been lurking on these forums for advice and I've come up with this: Please help me to understand if I'm correct, or give me other instructions to troubleshoot.

    1)Let the truck warm up and then check the heater hoses to the heater core. One warm at first, the other cool and then they should both be warm/finally hot after a couple more minutes. Note: I did experience a low coolant condition just last week... and had to add about 3/5 of a gallon to top off the system... checked yesterday and there was no noticeable loss.

    2) This is a procedure question... if the warm intake hose indicates hot coolant going to the core... does hot coolant in the return hose indicate that the heater core is functioning ok? i.e. passing the coolant successfully through the heater core?

    3)Check the blend door actuator.... I've seen a bit on this...mine is not clicking at all or ever which leads me to believe I have an issue with the heater core or coolant getting to the heater core.
  2. murdog94

    murdog94 New Member 1000 Posts 100 Posts

    If you had heat, and now dont, i have a few things. Are you still running the Dex Cool coolant (pink) if so there is a good chance that it has plugged your heater core. Also what temp does the motor get to? if it isnt getting to the normal range (190-210 degrees) then there is a chance that your Tstat is staying open and the coolant isnt getting warm enough to make the heater core work properly (yes the lines will be hot, but pressure, and actual temperature will be off enough to cause this)
  3. lowpost

    lowpost New Member

    Dexcool..

    I have always used the orange dex-merc coolant, never seen a pink coolant. I checked the hoses last night, with the heat on full temp and a/c btn on. the hose to the core is warm, but the other is cool. I would assume the core could be an issue. I read here about back flushing the core...is this a scenario calling for a back flush to unplug the core?
    I see your point as wellregarding the tstat. I'm gettting the temp, but my coolant loss has me guessing if the pressure is right.
    what's my next move?
    1) pay for a pressure test for a leak? or
    2) back flow the system on my own? I have one of those flush kits intalled inline between the heater core and water pump, can i connect it to water hose and disconnect the other hose end from the water pump altogether and flush into the cold hose, back to heater core, and out the disconnected line w/o starting the truck?
  4. murdog94

    murdog94 New Member 1000 Posts 100 Posts

    Yes you will want to back flush it (if that will do the trick it doesnt always work if the core is to far plugged) without the motor running and the hoses disconnected so you dont get any junk in the motor. As to Dexcool, that is the GM brand of coolant, and also what Dodge uses. It is Pink, the orange that you are talking about isnt the std coolant. So yes it sounds very much like your heater core is plugged up.
    As to the coolant loss, how long did it take to leak that down?
  5. BiG Chris

    BiG Chris New Member

    im having the same issue with my truck as well, heat is barely there if i turn the blower past 2 it gets cold. Ive got a new water pump and t-stat
  6. murdog94

    murdog94 New Member 1000 Posts 100 Posts

    Then you will want to do the same thing as well.. it isnt uncommon for the heater cores to become plugged.
  7. lowpost

    lowpost New Member

    FIXED IT! Now I have heat back, but why'd this happen in the first place?

    Thank you Murdog94. You confirmed my suspicions and so I did as suggested and now I have a heaping helping of heat again! So here is my next question, you've obviously speak as if you've heard of and or seen the Genuine Dex Cool pink or orange(see pic below) do this to heater cores... what is the solution or proper coolant product to use?
    http://dl.dropbox.com/u/41553636/IMAG0313.jpg
    Last edited by a moderator: Aug 20, 2014 at 9:16 PM
  8. japsmash2001

    japsmash2001 New Member

    The big issue is where is the coolant going? It is leaking it or burning it through the head gasket. I would go to a junk yard and replace the control module on the dash. If they don't have any. then it must be a common problem. Look on- line for the part.
  9. lowpost

    lowpost New Member

    FIXED IT! Now I have heat back, but why'd this happen in the first place?

    Thank you Murdog94. You confirmed my suspicions and so I did as suggested and now I have a heaping helping of heat again! Now my interest is piqued on the root cause of the problem and if my coolant choice is to blame. BTW, I did in fact have a good bit of rust flakes about this size: << A>> to exit from the hose on the ground. What is the solution or proper coolant product to use to avoid this? I'ts been about 5-6 months since I added any coolant. I'm not sure about any pink coolant, but my Auto zone guy says that Dex Cool is orange and may take on a slighter pink when you drain it. I asked about any regional differences, and he says its orange all over the country by law.... lol.

    So just to get on the same page with you regarding the issue is Dex Cool no longer what I should be using? You asked "are you still using Dex Cool" which seemed to suggest something better.....Thanks in advance again!
    [​IMG]
  10. BiG Chris

    BiG Chris New Member

    Looks like im going to have flush my heater core this weekend and see whats up with my coolant because its pink too ill have to change most of it out

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