Heater Core Revisited.

Discussion in 'KJ General Discussion' started by JBDive, Oct 22, 2018.

  1. JBDive

    JBDive Full Access Member

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    Good thought. I have one but generally looking at my phone to read it while driving isn't a good idea. I'll see if the app has logging built in. Considering I have a new, rebuilt engine and all new cooling system (radiator, water pump, therm, and some other crap) I should not be having any issues with the cooling system itself, outside of the heater core. Even replaced the clutch on the fan as I have the towing package so both mechanical and electric fan. Speaking of which man can I tell a difference with this replacement clutch. It is in full spin mode, loud as heck, for the first bit of driving.
     
  2. JBDive

    JBDive Full Access Member

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    I am referring to the inside filter under the dash which if clogged will kill your recirculating air speed. Under the glove box.
     
  3. TomB985

    TomB985 Full Access Member

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    You look at your gauges, don't you? What's different about a phone screen displaying a reading and a gauge on the dash?

    With all those new parts you're probably correct, I was just trying to suggest a cheap way to rule out an inexpensive thermostat that could cause a similar concern.
     
  4. tjkj2002

    tjkj2002 Full Access Member

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    My '02 would be at operating temp in less than 2-3 miles even at 0 degrees,blowing good heat before the 1/2 miles if I started driving shortly after actually starting the engine.

    At full operating temps the outlet temps in the center of the dash was 165-170 degrees on high fan speed,closer to 180 degrees on the lowest fan setting.
     
  5. Aceofspades

    Aceofspades Full Access Member

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    Sounds like you had a perfectly working heater core. I have zero plans to replace mine but it does get hot - just not at the same time the engine is up to temp.
     
  6. JBDive

    JBDive Full Access Member

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    Engine Coolant Temps
    195 Degrees at highway speed, air temp low 40's to mid 30's
    200 Degrees at city speeds, air temp low 40's to mid 30's

    Heater Selection on Vent, full hot, low fan speed
    Vent temps at highway, 125-130
    Vent temps at city, 130
    Vent temps parked, 135-140

    New Observation:
    Selecting Defrost or Defrost/floor the temps are FAR cooler, 90's maybe. Come back to vents, give it 5 mins or so and temps are back to 125-135. With fan speeds over second speed the temps drop to low 100's. Getting a lot of fresh air through heat selection which is noticed if I drive by smoke or a stinky car.
     
  7. GitEmSteveDave

    GitEmSteveDave Full Access Member

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    According to the service manual:

    Ambient Air Temperature
    15.5° C
    (60° F)
    21.1° C
    (70° F)
    26.6° C
    (80° F)
    32.2° C
    (90° F)

    Minimum Air Temperature at
    Floor Outlet
    52.2° C
    (126° F)
    56.1° C
    (133° F)
    59.4° C
    (139° F)
    62.2° C
    (144° F)
     
  8. Aceofspades

    Aceofspades Full Access Member

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    Damn... all the time I spent messing around with both jeeps I never noticed that ...
    Thanks - going outside now to look
     
  9. willowyric

    willowyric New Member

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    I'm in the same situation. Just had my core flushed, but still cool air when driving. Torque app shows my coolant temp between 195 and 197 while driving. As soon as i come to a stop the vents start blowing warmer air.
    I actually just requested my local shop to replace the thermo and they instead flushed the core. They reported that the core seemed to have good flow, but didn't replace the thermo since the engine seemed to be heating up fine.
    So to review; core was checked and has good flow. Vents blow hot when left to idle. Driving causes the vents to blow warm, or cool air.
     
  10. Joenavy85

    Joenavy85 Full Access Member

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    Very odd, typically the problem I hear is that it's blowing cold while idle and warm to hot while driving, which indicates low coolant. I'd have to look at a proper system diagram to know for sure, but I'm going to guess that it's a thermostat problem.
     
  11. tjkj2002

    tjkj2002 Full Access Member

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    Classic heater core restriction problem.

    Look at the pic I posted of the heater core in a KJ.Fully plugged you will still have "good flow" through the hoses and core with both the inlet and outlet on the same side that can bypass the actual core itself.
     
  12. billp2000

    billp2000 New Member

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    Same problem. Car operates well but with no heat; heat indicator on dash indicates proper heating/cooling. After multiple flushes (back and forth) soaked heater core in CLR for three days then flushed. Water flows freely and clear both directions. Both hoses hot when car reaches correct temperature. Water flows clear when hoses disconnected. 2002 Liberty Limited. If the heater core is completely clogged will water still flow through?
     
  13. ltd02

    ltd02 Comfortably numb KJ Supporting Member

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    Are you sure your blend door is working?

    Pretty sure water will flow freely even if the core is plugged. It will just bypass to the outlet and not reach the plugged heat exchanger portion.
     
  14. uss2defiant

    uss2defiant Full Access Member

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    did you read tjkj's post?