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'00 300m - very little heat from heater

Discussion in 'LH: Large Cars, 1993-2004' started by MoPar~Man, Nov 22, 2015.

  1. patricklynch

    patricklynch Mopar starship captain

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    Interesting you mention Ford in that context. When we were poor college students in the 1980's, I had bought my then wife a '65 1/2 Ford Galaxie 500 that ended up having a leaking heater core. All you had to do it was disconnect the hoses, remove a cover and pull the heater core straight out of the firewall. Unhappily, that core was also made of unobtanium at the time and I couldn't get a replacement for it. Gave me my first experience with JB Weld. lol.
     
  2. valiant67

    valiant67 ...

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    Ford did seem to make heater core repairs easier - I think it was Dad's 78 LTD that had an access panel for the heater core and then Mom's 1984? Crown Vic had an access panel for the fuel pump.
     
    patricklynch likes this.
  3. AC TC

    AC TC Well-Known Member

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    Anyway, do a backflush first, my durango had the exact same symptoms and both hooses were hot.
    ( i belive that it only flowed water in a few rows. )
    What came out looked like rusty ketchup, large amount of rusty ketchup.
    I have had to repeat this flush a couple of times when it started to have to lousy heat.
    I have not used any chemicals, just plain warm water and added some compressed air into the mix.
    - i just held the water hoose and the blowgun against the hoose end that came from the core, giving it airbursts into the water.
    I did get wet..
    - disconnect both hoose, dont blow the junk into the engine.
     
  4. manybrews

    manybrews Well-Known Member

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    Unfortunately, testing the inlet and outlet temp of the heater core really doesn't tell you much.

    It is useful in knowing that there is likely flow through it, but clogging is not the only issue that would prevent heat.

    Chrysler had a lot of issues with calcification inside the heater cores (and radiators as well).
    Coolant may flow through the assemblies, but little heat transfer occurs.

    A chemical flush MAY help that, but likely not. Replacement is recommended.
    Of course, first you do need to verify that the blend doors are working correctly, and that the temp of the coolant is actually to spec.

    But I would not be surprised if a heater core is needed.
     
  5. MoPar~Man

    MoPar~Man Active Member

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    I plan on doing an inner tie-rod bushing replacement in the next few months, and hence will be able to access the heater hoses at the firewall and see what I can do in terms of flushing the core (with what-ever I can think of - full-pressure garden hose, recirculating various chemical concoctions, etc). This has been an incredibly mild winter, and the car is kept in heated garage overnight every night, so I'm not that bothered by this lack of heat from the core.

    One thing I do notice is that setting the climate-control to the recirculate setting (recirculating interior air) does increase the heater air temp within a couple of minutes, and sometimes I would say the air has actually felt "hot" - but my recollection is that the air doesn't stay hot for more than a few minutes. The fan speed also seems to change automatically to a higher speed when the setting is changed to recirculation (don't know why). But most times during cold weather the amount of time I can have the setting set to recirculation is limited due to interior window fogging.

    I've performed the 3-button HVAC test (with the blend door motor mounted and dis-mounted from it's installed location) and the blend door motor and position sensors seem to be working as expected. One thing I was thinking of trying was to drop to blower motor (seems that it can be done without dismantling much more than the glove box and associated trim panels). It should be possible to get a look at the heater core (either directly or with a video device or camera) if the blower is removed. ?
     
  6. Tomguy

    Tomguy Well-Known Member

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    My M had no heat. I didn't know why until I found out I had almost no coolant. I wasn't overheating because winter I guess? Temp gauge read fine. But it took a gallon of coolant. turns out my only 4 year old radiator was split. How is your coolant level, and have you bled your system?
     
  7. MoPar~Man

    MoPar~Man Active Member

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    > How is your coolant level, and have you bled your system?

    I replaced the (original) rad about 13-14 months ago. Coolant level was fine at the time (I've never had a coolant leak or have had to add coolant prior to replacing the rad). I replaced the rad because it got punctured while driving, otherwise it seemed fine (not rusted or obstructed with debris on the outside). When I replaced the rad, I didn't flush the system, so I don't know how much coolant there was left in the engine after the new rad went in. I've been noticing that the heater had been putting out less heat than it should for maybe the previous 2 winters.

    After the new rad went in, I topped it up such that the fluid level is maybe an inch under the rad fill cap on the plastic reservoir. It is still that high today. After more than a year of driving I would think that all the air is purged out even if I didn't bleed it properly (but I did mess with the small bleed screw at the top-front of the engine so I'm pretty sure I bled most if not all the air during refilling).
     
  8. Tomguy

    Tomguy Well-Known Member

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    There's one thing you can try, and that's a flush of the core, but it likely won't be easy to access (unless you can do the crossmember quick). I will admit I flushed mine when I replaced my evap so I am going off memory here, but you will likely need to pull the wipers and two cowl pieces, and then the crossmember. I can now do that in under 10m after having done it so many times. It should give you access to the hose clamps where the hoses go into the core. Don't go too high with pressure, I'd suggest a mild citric acid solution or if you are hard-pressed to find it pure vinegar in the core (use a shop vac to pull the old coolant out first of course). Leave it in overnight. Again suck it out with a shop vac. If you want to be thorough, after letting it sit and sucking it out, dissolve about 3 tbsp of baking soda into a cup of warm water, put that in the core, and then fill with vinegar slowly, let the bubbling stop, then flush with water. Vacuum that out, then fill with your coolant/water premix, reattach the hoses, and see what's what. I did that on my old MB that had poor heat instead of pulling the core, and it actually worked. And got some yummy gunk out too.
     

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