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Why can I get no interior heat in the winter? (300m)

Discussion in 'LH: Large Cars, 1993-2004' started by MoPar~Man, Nov 10, 2018.

  1. MoPar~Man

    MoPar~Man Active Member

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    I've got this plan, when I've got some time and it's not freezing cold outside, to get at the coolant lines going to the heater core and cut / remove them from the core and somehow rig up a couple of garden hoses and just flush the poopies out of the core, have the out-flow run to a sewer grate. Then reconnect the lines.

    In the middle of summer, if I set the interior temperature to "hi" (which is all the way up), the air the comes out of the vents is very very hot. If, say a week ago when the ambient air is 40f, the vent air is also hot, or reasonably hot. Certainly enough to bring the cabin up to room temperature quickly. But today, the ambient is 25f (way below normal) and the engine temp gauge is right up to operating temp but the air coming out of the vent is luke warm, or maybe a bit less. Where is the heat?

    I know there is a self-diagnostic test you can do by pressing the right buttons and the fan and the various internal doors/gates open and close and every time I've done it I get a pass (haven't done it this year yet, but I suspect it will pass). Last year I struggled to get the blend door motor out (what a pain!) and watched it operate during a test and it seemed to work fine.

    So I'm back to plan-A which is the flush the core before winter sets in, but I really can't figure out why I get plenty of heat out of this thing in the summer and really any time the ambient outside air is over 40f (or maybe even 35f) but below that the heat really drops off fast. The only other thing I can think of is that the electronics is malfunctioning at low temps and keeping the blend door open too far?
     
  2. Tomguy

    Tomguy Well-Known Member

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    Air bubble in the cooling system. Crack open the bleed valve on the lower intake manifold when the engine's running, and keep it open until the bubbles stop. I usually connect a tube, since it's designed to do that, and run it through the loop in the hood that goes in the latch, so I don't make a mess - and to be sure the bubbles stopped. Then I close it with a 10mm open-end wrench.
     
    patricklynch likes this.
  3. voiceofstl

    voiceofstl Well-Known Member

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    I had a 85 chevy van that did the same thing.
     
  4. ka9yhd

    ka9yhd Well-Known Member

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    Also check the water valve. When flushing the heater core, blow through both hoses to agitate and help remove any debris.
     
  5. Tomguy

    Tomguy Well-Known Member

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    Be careful if you choose to flush. The LH cores are known to leak if you do and that's a dash out repair. There's no valve in the LH either. Just the blend door. I said air bubbles because that happened to mine, and these cars are notorious for air bubbles and the heater core is a high point in the system flow.
     
  6. patricklynch

    patricklynch Mopar starship captain

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    Agreed on the air bubbles. When I got my '02 Concorde Lxi, it was pretty clear, it was an all original car and probably including the antifreeze (152,000 miles). It was an enormous pain to bleed the air out of the system with the heater core so high. It's a shame there wasn't a bleeder valve at the heater core that would have been accessible. I was also told that the core tubes were smaller and easier to clog. I don't know if that is true or not, but it wouldn't surprise me.
     
  7. 2012srtchallenger

    Supporter

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    have had good luck backflushing (flush opposite of coolant flow)heater cores until I ran into 2012 Chrysler 200.due to new designthey seem to take path of least resistance and wont back flush.i would try flushing and see what happens. I did end up pulling dash and replacing core
     
    #7 2012srtchallenger, Nov 25, 2018
    Last edited: Nov 25, 2018
  8. dana44

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    If it was flushed once within the past five years there is no way it should need another flush. You either have air in the system, which can be a pain in the rear to get out, or, simply because of the outside temp you are not having the doors of the system operate properly. Vent control doors break, vacuum lines leak and don't operate doors properly, and foam rubber used to seal different conditions (heat, AC, outside air, recirc air, etc.) can be compromised, thus adding heat when 25F temp is blowing at 50mph through a vent takes the temp well below -10F to cool and blow across the heater core, so, check to ensure the systems are functioning properly to start with given you said the engine temp itself shows up to normal operating temp. Pain to pull this stuff apart to ensure it is working and sealed properly, but there is one thing you can actually do, which I have done myself in times like this, and that is, add a piece of cardboard to the bottom half of the radiator front (so it stays in place). What this does is cuts back on the cooling of the fluid itself, and given the temps are below 50degreesF, no harm will occur, but, it will prove that it is not just so darn cold out there that it can't keep the car warm. If it does indeed help warm the car, then it is indeed pretty darn cold out there and it isn't a mechanical failure under the dash.
     
  9. Tin Man 2

    Tin Man 2 Active Member

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    I once had a heating issue also, my problem turned out to be the Anti Freze was mixed to “rich”. Turns out that anything over a 50/50 mix hurts the ability to absorb heat. Who knew.
     

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