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jeepske 10-06-2011 12:14 AM

heater core mystery leak
Hello all, my 94 gr.cherokee 230K shows a coolant leak on the garage floor, just a seep. If you drive it with the heat turned off then there is little or no leak when it's been parked. If you do turn the heat on, then coolant fogs the windshield a little and of course, smells. No leaks on the cabin floor, but after parking, there will be that seep on the garage floor. Seems to be coming front passenger front of engine, not by the water pump (which as been replaced twice, by me, at 100k intervals). Replacing the heater core seems like a big deal, so I'm troubleshooting everything else I can think of first. Your help is most appreciated. Jeepske.

2005JGC 10-06-2011 01:38 AM

Re: heater core mystery leak
If your steaming up the windows, especially if it comes with a sweet antifreeze smell, I am sorry its likely the heatercore. I am not sure exactly what the box looks like from the top of my head, but the leaking coolant may be draining out of the hvac box drain which IIRC is near the right frame rail by the firewall.

If the reservior is being overfilled it may be dumping coolant out of the overflow tube on the reservior. Also radiator, radiator cap and lower radiator hose would be suspect for a passanger front leak (assuming this is a V8), if its an I6 it would be the upper hose or radiator or radiator cap.

jeepske 10-06-2011 01:41 PM

Re: heater core mystery leak
Thanks for the reply. So, heater core replacement, I believe, requires removal of the dashboard! Any tips, tricks or shortcuts to this job? or is it possible to get technical info on what procedure to follow?Thanks

2005JGC 10-06-2011 02:05 PM

Re: heater core mystery leak


This revised Heater A/C Housing service procedure is referenced from Technical Service Bulletin No: 24-02-98.
  1. Disconnect battery. This must be done to prevent accidental airbag deployment.
  2. Using on A/C recovery unit, remove all R-134a refrigerant from the A/C system. See: Service and Repair
  3. Remove the shift knob by pulling sharply upward.
  4. Place the transfer case in low range. Pry the shift indicator bezel out of the console using a trim stick.
  5. Apply the parking brake and place the transfer case in neutral. Remove the parking brake trim insert. Remove the console attaching screws. Lift the console up and disconnect the 4WD indicator lamp hamess. Remove the console.
  6. Remove the passenger side knee blocker. Remove the single end screw. Remove the screws below the glove box. Remove the screw at the courtesy lamp. Remove the ash receiver and the screws behind it. Remove the instrument panel armature screw behind the ash receiver. Open the glove box and remove the screws behind it. Lower the panel and disconnect the lamp harnesses. For additional instrument panel service procedures to complete steps 6 thru 25, refer to Instrument Panel, Gauges and Warning Indicators/ Instrument Cluster / Carrier/ Service and Repair/ Procedures. See: Instrument Panel, Gauges and Warning Indicators\Instrument Cluster / Carrier\Service and Repair
  7. Remove the pod switch bezels on both sides of the steering column with a trim stick.
  8. Remove the drive side knee blocker. Remove the end screw and screws located at the bottom of the knee blocker.
  9. Remove the cowl top trim panel by prying it up with a trim stick. Remove the solar sensor if equipped.
  10. Remove the "A" post trim panels.
  11. Remove the remove the bolts that attach the lower instrument panel reinforcement to the instrument panel armature and remove the reinforcement.
  12. Disconnect the park lamp switch.
  13. Pull back the carpet at the transmission tunnel from the base of the instrument panel center bezel. Remove the nuts from the upper studs and bolts through the floor that secure the instrument panel center bracket.
  14. Remove the bolts that secure the instrument panel center bracket to the drivers side of the transmission tunnel.
  15. Remove the screws securing the Vehicle Information Center and remove it. Remove the screw fastening the mounting bracket.
  16. Unplug the vacuum harness connector or vent tube on ATC equipped vehicles and the wire harness located under the passenger side of the instrument panel.
  17. Remove the screws holding the passenger side kick panel, along with the screw from the kick panel shroud.
  18. Unplug the antenna cable near the right cowl side panel.
  19. Unplug the instrument panel wire harness connectors from the junction block at the right cowl side panel.
  20. Remove the bolts that secure the instrument panel armature to the windshield fence.
  21. Remove the nuts that secure the top if the instrument panel armature to the windshield fence.
  22. Remove the bolts that secure the ends of the instrument panel to the cowl side panel.
  23. Remove the nuts that secure the steering column to the brake pedal support and lower the steering column.
  24. Remove the bolts that secure the instrument panel armature to the brake pedal support.
  25. Place a protective cover on the seats. Lift the instrument panel off the windshield fence studs and maneuver the instrument panel out and lower it onto the seats.
  26. Disconnect the refrigerant lines from the evaporator tubes. Make sure to install plugs or tape the ends of the lines and fittings to ensure that excessive amounts of moisture do not contaminate the A/C system.
  27. Remove the vacuum line at the tee from the main vacuum supply harness. This line runs through the body with the upper refrigerant line.
  28. Disconnect the heater hoses from the heater core and clamp the ends closed to prevent coolant loss. See: Heater Core\Service and Repair
  29. Remove the coolant overflow bottle.
  30. Remove the Powertrain Control Module with connectors intact and set aside.
  31. Remove the heater A/C housing mounting nuts from the studs on the engine compartment side of the dash.
  32. Remove the heater A/C housing from the vehicle.
  33. To Install the components, reverse the procedure stated above.
Torque Specifications:
Instrument panel center bracket to floor transmission tunnel fastener: 28 Nm (250 in. lbs.)
Instrument panel to windshield fence bolts and nuts: 12 Nm (105 in. lbs.)
Instrument panel to cowl side inner panel bolts: 12 Nm (105 in. lbs.)
Instrument panel to steering column support bolts: 12 Nm (105 in. lbs.)

Personally I have not had the dash out of a zj, if it was a wj I would have tips and be able to tell you where the hidden screws are... but not the zj. Note it will require evacing and recharging the A/C, While your in there I would halfway suggest replacing the evaperator (if your a/c still works ;) ) its just one of those things, you can do the job once right or risk having to do it a second time for an a/c leak. we always suggest replacing everything, considering the wj we charge 7 hrs plus 1 hr evac and recharge so 8 hrs to so for 800+ dollars labor it is naturally suggested that the entire hvac box is refreshed while we are in there.

jeepske 10-08-2011 04:46 PM

Re: heater core mystery leak
Hey thanks, looks like a ton of fun. I'm able to access those tech manuals at Alldata through my public library's account and then print out the pages I need. Thanks again for so much help.

2005JGC 10-09-2011 12:17 AM

Re: heater core mystery leak
that will look VERY familiar to you then, thats where I got it ;) (less the pictures)

jeepske 11-22-2011 10:20 AM

Re: heater core mystery leak
Well thanks again for the support. Got the job done, what a beast!!, needed help undoing the A/C lines (special tool required) and also locating the hvac box studs going through the firewall (no description in the manuals). replaced the offending heater core with oem part (Napa part was aluminum -made in China). now all is well, coolant leak has vanished! warm Jeep. thanks.

2005JGC 11-23-2011 04:39 PM

Re: heater core mystery leak
Awesome, Glad to hear!

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