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ND-TECH, CJDR Master Tech
Category: Jeep
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Experience:  ASE Certified CJDR Master
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2000 cherokee sport: heater..luke warm air..radiator..overheating

Resolved Question:

i have a 2000 cherokee sport and the heater only blows luke warm air it has a new water pump radiator and thermostat thogh when it was overheating i put a 185 degree thermostat in it any ideas
Submitted: 6 years ago.
Category: Jeep
Expert:  ND-TECH replied 6 years ago.

You still have air in your cooling system most likely. That is the most common cause of low heat in the passenger compartment after a repair on the cooling system. This is the proper fill procedure.


  • Fill system using a 50/50 mixture of water and antifreeze as described in the Coolant section of this group. Fill radiator to top and install radiator cap. Add sufficient coolant to reserve/overflow tank to raise level to FULL mark.
  • With heater control unit in the HEAT position, operate engine with radiator cap in place.
  • After engine has reached normal operating temperature, shut engine off and allow it to cool.
  • Add coolant to reserve/overflow tank as necessary. Only add coolant when the engine is cold. Coolant level in a warm engine will be higher due to thermal expansion.

    You need to have it on full heat due to the heater control valve on the heater core lines. When not in full heat this valve is closed and will allow air to stay in the heater core. When opened it allows air into the cooling system and will cause low heat. If this procedure does not work then your heater control valve has probably failed

    ND-TECH and 2 other Jeep Specialists are ready to help you
    Customer: replied 6 years ago.
    where is the heater control valve located on the 2000 cherokee sport?
    Expert:  ND-TECH replied 6 years ago.
    If your vehicle has one, which I dont remember if they stopped using them on after 99 or 2000 it will be located on the heater core lines that come from the engine to the heater core. You most likely have air is your system though. Also if you turn your a/c on will it blow full cold?
    Customer: replied 6 years ago.
    i ran engine with heat wide open let cool down completely overnight topped off coolant resevoir same result luke warm air there is no heater control valve
    Expert:  ND-TECH replied 6 years ago.
    Ok, well if when you switch from hot to cool will it go to full cool or does the temp stay the same? Also when you switch the temperature can you hear the blend door move?
    Customer: replied 6 years ago.
    cant really hear the door my hearing is not good but it does get cool when switched to cool
    Expert:  ND-TECH replied 6 years ago.
    Ok well with it switching to full cool then that tells us the blend door is working properly. Also since you did to correct procedure for filling the cooling system then we also know that is good and all other aspects of the system are good since you replaced them. Most likely you have a clogged heater core then and it is not letting enough coolant flow through it therefore not allowing any heat into the passenger compartment. First thing to try is to remove both heater core lines where they attach to the heater core under the hood. Then take a garden hose and put it to one end of the heater core and turn it on. This will hopefully flush out any clogs but it is not a guarantee. If this does not correct your concern then you will have to replace the heater core to correct it.
    Customer: replied 6 years ago.
    i did run water through the heater core yesterday though not with a garden hose i used a funnel and poured it through it did run through seemed slow to me but i wasnt sure how fast it should run through
    Expert:  ND-TECH replied 6 years ago.
    It should come out just as fast as it goes in. Also you need to use a garden hose since you need the pressure thats behind to help force any clogs out of it
    Customer: replied 6 years ago.
    ok will try that tomorrow and let you know thanks
    Expert:  ND-TECH replied 6 years ago.
    Ok let me know what happens
    Customer: replied 6 years ago.
    heat works now great advice thank you