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It's winter, so heater problem is back ('00 300m)

Discussion in 'LH: Large Cars, 1993-2004' started by MoPar~Man, Dec 20, 2016.

  1. Tomguy

    Tomguy Well-Known Member

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    If your hoses are that hot, chances are your heater core is filthy, missing fins, and/or plugged inside. Or a combo of all of these. The only true solution would be to replace it. Now, that being said, I do believe with the engine at operating temp the coolant in those hoses should be about 200 degrees - rubber isn't really a great heat conductor, so maybe put a sensor on the thermostat housing. One thing I have an issue with mine, is that I have a GARBAGE A/M thermostat in and I never get to operating temp in the winter because the thing doesn't close fully.
     
  2. MoPar~Man

    MoPar~Man Member

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    On a recent 2-hour highway drive (flat, constant speed 70 mph) with cabin temp set to 70f (not set to "Hi") with outside temp ranging from 45 to 56 f, the temp of the 2 heater hoses leading to the heater core averaged 148 f and 130 f. When compared to outside ambient, there was a very slight increase in both temps on the order of .1 f and .4 f degree per degree change in outside temp. On the return drive, outside ambient was 42-44 f and the two hose temps were 147 f and 127 f.

    The two heater core ports are side-by-side on the engine firewall. The hose connected to the one on the right (on the driver's side) is the hose that reads higher temp. Both of these hoses are short (I'd say less than a foot long) and I wrapped a short section of black-foam pipe insulation around them at the point where the temperature probes were placed. This is the black foam that comes in 3-foot sections that you put around copper water pipes. This was to insulate the probes from the cooling effects of being exposed to air drafts while the car is moving.

    One odd thing that I noticed: After the 2-hour highway ride, I travel for another 15 minutes on lower-speed county and city roads. During this time, the hose temp readings change quite a bit. They went to 155 / 160 (on the first leg) and 149 / 156 (on the return leg). In other words - what was the cooler hose now became the hotter hose. So either the coolant was picking up heat FROM the heater core (coolant flowing into the heater core became warmer by the time it left the core) or the flow of coolant became reversed.
     
  3. peterjon1

    peterjon1 Well-Known Member

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    My car sits outside; at 3 deg F, from a cold start, I get 155 - 160 deg at the center dash vent after about 10 minutes in my Stratus, which means the heater inlet has to be warmer than that.
    Put one of your temp probes on the upper radiator hose and see what happens, should be ~ 195, depending on your thermostat.
     
    #23 peterjon1, Jan 23, 2017
    Last edited: Jan 24, 2017
  4. pt006

    pt006 Active Member

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    Mopar man; It is important that the heater hoses are routed correctly. -------- Check the radiator cap when the engine is cold. It must be full to the top, or air is in the system.
     
  5. movinyou

    movinyou Active Member

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    I had the same problem earlier this fall after using some stop leak(that's another story). I ended up pulling the cowl, cutting the end off a 3/4" garden hose and reverse flushing the core. Since the flow is outside hose to inside hose, a reverse flush is the best way to go. Pull both hoses going to the core at the firewall, put your garden hose on the inside (drivers side nipple) and with very low pressure, turn on the hose and watch what comes out the passenger side nipple. it's amazing how much junk will come out. let it flow until the water is clear. After I did that, I had 145 degree vent temp. on a 0 degree day. How this helps you.
     
  6. peterjon1

    peterjon1 Well-Known Member

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    I replaced my Stratus with another vehicle, and had the issue of not enough heat. I was getting at best about 100 deg out of the center vent with temps in the teens. Could not defrost the windshield even. Shop said 100-110 was good. I said flush it anyhow. Now I'm getting 158 deg. World of difference. Flush the heater core.
     

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