[kadetklapp]

This stupid thing is killing me. I've got NO heat

I can't handle this all winter. Here's the run down-
1999 Jeep Cherokee Sport
4.0L
182,000 miles
Air conditioning works fine
Blower motor resistor pack shot, fan only works on highest setting.

Blend door motor works and turns properly, as it should.

"Flushed" system back in October with garden hose. Removed both heater hoses, and confirmed that there is some flow thru the heater core.

Nasty, filthy crap came out of the system: looked like someone used Dexcool in it. I flushed a few different times with water and fresh green coolant.

No overheating or underheating.

No coolant leakage under core/in cabin, no coolant smell.

Thermostat opens properly at 200-210 degrees, and drops to 197 degrees (verified with scangage II).

Luke-warm air comes from vents with heat at highest setting.

Wrench-head friend felt bottom heater hose when heat at highest setting and thought it felt "cooler" than the upper hose

The best Christmas present I could get right now is some heat. I'm really in a bind. Help a guy out and let's figure this thing out

[Shane01638]

Do you get more heat when the RPM's are revved higher? That's what mine did so I replaced the water pump. That didn't make a difference, but it's fine for me even below 0'. I just had a winter front made for it so it will warm up quicker. I had the zipper put on the air intake side so I can open up the front and let cool air cool the intake air. If you do go with a new water pump, look at this:

http://go.jeep-xj.info/HowtoWaterpump.htm

I think that would push more coolant to get better heat, and better cooling in the summer. I wish I would have did this when I replaced mine...still thinking about it.

[kadetklapp]

No, RPMs make no difference whatsoever.

[JFM626]

[QUOTE=kadetklapp;6113689]This stupid thing is killing me. I've got NO heat



"Flushed" system back in October with garden hose. Removed both heater hoses, and confirmed that there is some flow thru the heater core. "

Are you satisfied there is enough flow? If so then the problem may be the exterior of the heater core is filled with duff and preventing heat from being dissipated through the fins. You can sometimes diagnose this by having the fan on high, and with the engine warm you should find one of the heater hoses considerably cooler then the other one (indicating that the heat has been removed by the fan air blowing across it). If not then that may be the cause.

"Nasty, filthy crap came out of the system: looked like someone used Dexcool in it. I flushed a few different times with water and fresh green coolant."

You may not have gotten all the crud out, the smallest orifices are located in the rad and heater core, sometimes reverse flushing the heater core can force small pieces of debris out, when regular flushing just makes it worse. You can use a garden hose gut remember house pressure is about 60psi while the pressure in the cooling system is only around 12psi.... so be careful about building any pressure up

"Wrench-head friend felt bottom heater hose when heat at highest setting and thought it felt "cooler" than the upper hose"

The lower rad hose should be noticeably cooler, see if you can borrow an infrared temp gun to verify temps

[kadetklapp]

Thanks for the replies-

Are you satisfied there is enough flow? If so then the problem may be the exterior of the heater core is filled with duff and preventing heat from being dissipated through the fins. You can sometimes diagnose this by having the fan on high, and with the engine warm you should find one of the heater hoses considerably cooler then the other one (indicating that the heat has been removed by the fan air blowing across it). If not then that may be the cause.

I'm not satisified that there is enough flow, simply because I don't know how much is enough. The heater hose was cooler when the fan was on high, as my wrench-head friend stated. By the sounds of it, it's probably my core.

SO, should I get some radiator flush and try flushing it one more time?

[oldmanscherokee]

make sure your backflushing it as well, flush it out both ways, make sure the vacuum valve is working correctly if the truck has one. once it all wamred up and running grab the hoses. youll know where your coolant flow is stopping. if you have the fan off and one hose is cool still youve got a bloackage. with the heater off and the valve allowing flow both hoses should be close in temp. with the heater on high one should be noticably cooler. if your absolutley sure the blend door is working then you have a coolant flow issue. your core may be clogged. even with all the crap that flowed out of it it still could be clogged enough to not allow enough flow to keep it hot with the airflow across it

[collkid]

Well my heat always seems a lot "cooler" when its on High.

and really hot when its on low...

[kadetklapp]

Well, there's no heater valve on this beast, so in theory there is coolant present in the core, since both hoses are hot with the fan off. When I turn the fan on (I've got high only, remember) one of the heater hoses cools considerably.

Oh, and I did flush the core both ways. There is a narrow pipe and wider pipe, not sure which is in or out, but I did flush both ends, and water came out both.

[JFM626]

Ok. Now I don't drive a Cherokee, but you may find that the heater core is plugged on the outside. If you live in an area where you drive on a lot of dusty roads with the fan on, it is possible that dust etc has entered the heater air intake and is now between the fins of the heater core. I have no idea how to check it on your Jeep other than to suggest that, if you can, blow out the heater core with compressed air from inside the cab back into the air intake, where you can have a vacuum suck up any dust that the air forces out.

[jeeptown]

Maybe your problem is getting the air to flow through the heater core. I've seen cores almost completely plugged with hair, fuzz and dust. I dont know any other way to clean them but to remove your plennum. In that case you would be better off replacing the core and probably youre evaporator too while youre in there.

[TallyZJ]

One other suggestion:

Do you ever hear water sloshing sounds when you make a tight turn? Sloshing coming from right side/passenger floorboard area?

If so, your heater core box may be full of water and not draining. YOu may need to unclog your A/C box drain tube located under the passenger side exterior firewall. Its a black rubber hose that sticks out of the firewall just near the frame rail.

If the box was to be clogged with leaves and debris and allowing water to collect there, it would cause your heater core to cool down too much and cause air not to flow over the core itself.

[kadetklapp]

No sloshing, no evidence to suggest a plugged external fin either. There is however, a hole in the heater box about the size of a golf ball. Obviously broken out somehow, sorta strange.

[TallyZJ]

It probably was clogged at one time and that was a jack-leg method of clearing out the trash inside without removing dash.

[kadetklapp]

Ok, my mechanic (certified) friend and I took it in the shop after hours and nosed around one more time.

The heater hoses were plenty hot, both in and outflow. He double checked my work, and found that the stepper motor for the blend door is not turning, it's actually majorly stressing when on the hot setting. It actually cracked the plastic axle that goes into the heater box. We removed the motor, confirmed it's function, and tried using a large blade screwdriver to turn the door. No way, no how, using as much strength as both of us can must (and we are pretty big guys) we could only budge it maybe a quarter, to a half a turn. The air was pretty warm while in the shop, but outside it went right back to luke/chilled air. So, he's thinking I need a "heater treater" kit. I hope he's right....

[FrankZ]

Heater core is partially plugged internally, that's why you're only getting a little heat. Time for a new heater core.