Need help with heat!

Hey everyone... Im new here but I have been in to XJ's for a few years now. To start, I have a 98 Jeep cherokee that I bought bone stock with plans of lifting it / making it everythign I every want in an XJ before even had the title. I went from this:
Then I changed out the motor for a 4.0 with 50,000k (old one had bad bearings), put in a rough country 4.5" long arm lift kit, 8.8 swap in the rear and hpd30 front both with 4.10s, aussie locker in the front and ford trac loc LSD in the rear rear thats currently getting rebuilt with more clutch packs.
Thats about the basics, other than small things like a custom rear bumper, and HID's in h4 housings that im soon replacing with projector housings, durango steering swap, etc. Currently running 31x10.5 sumitomo HTR all terrains for the winter, summer tires are brand new 34x9.5 swampers. All work done myself in my garage.

Pictured here with bald 33's...





ANYWAYS..now that you know what im driving / dealing with ..

I have had off and on (mostly off...) heat for, well.. since if owned the jeep. I have flushed the whole coolant system, and I flushed the heater core with CLR and it flowed right through, there was no clogs or anything.
So, I put it back together, put a new radiator in it, and a new thermostat (that seems to be working, stays right at 210. Old working thermostat sat it right at 180).
So after all that, I parked it up on ramps in the driveway, pulled the rad. cap off and let it run for probably 20-30 minutes until all the air bubbles came out. The heat worked pretty good for about a day, then went back to just air..
The next week, did the same thing, thinking maybe more air bubbles were trapped inside the coolant system. I burped it for another 30 minutes and then re-filled with coolant as needed. The heat worked for about 2 days, then died off. It is luke warm at best now.

I dont have a cap for the overflow bottle, so for now I have been covering it with tape (redneck, I know).

The top heater core line is pretty hot, the one below it (retrun line) is not as warm, but nonetheless pretty warm.

I noticed that its harder to turn it from hot to cold, than it is to turn it to from cold to hot. Hot to cold I feel like the knob has some kind of air pressure resistance (vaccum?). When I turn it to hot from cold, I dont get that "compression" feeling. Could this be something to look in to?

I am trying to narrow it down.. I hope I dont have to change the heater core but to me thats looking like the only rthing left. Hot air is deffinatly getting in to the heater core, and being dispersed somewhere from the heater core because the return line is not as hot, so the heat is deff. going somewhere. Is there anyway that a blend door is stuck open letting cool air in with the hot air? How hard are the blend doors to fix?

This should be in OEM tech, not modified. Ask a mod to move it for you, you might get better help there.

K. Sorry.. The OEM said tech on OEM or factory jeeps which mine is not so I put it in Modified since axle swap lifted locked and motor swap is modified IMO.

Anyone have any ideas (other than that this is in the wrong tech section) :compwork:

Help is greatly appreciated!

Do the 98's have a heater hose valve under the hood like the earlier XJ's do? If so I would keep an eye on that and make sure it's working as it should be.

Addicted, look at the heater control valve, make sure the heater lines are both hot when the heat is on at the fire wall. Heater control valve works on vacuum, so if you applied vacuum to the valve the arm on the valve will open or close, a quik way to see if valve arm is moving put it on hot (look at where the arm pointed, put it on cold, it should move other way. Hot both lines are hot ,cold, one hose line not hot at fire wall. The heater valve stop the flow to the heater core. If it checks out ok, check the a/c -heater blend door for opening & closing.Thats all the help that i can give you at this time,PS alway's check the little things 1st. 92xjjeep rockon..

he does not have a heater control valve. it was done away with by 98.

I have bad heat in my 96 XJ too. Flushed the whole system before winter hit, because of how mediocre it was last year. I also broke the heater control valve in the process, so I just did away with it. It's only enough heat to melt the snow as it hits the windshield and let it refreeze as ice which ends up being a sheet of ice if I try to use the wipers. If I drive long enough to get the whole cabin warmed up, then it keep most of the windshield clear, but this is not a problem I ever had in my 87 XJ, so I know something has got to be wrong.

Temp gauge is right where it should be, so I'm pretty sure there is nothing wrong with the thermostat. My next step is going to be some CLR, not expecting much though. When flushing the heater core, it seemed very free flowing. I'm wondering if maybe the heater core is clogged up with dust or whatever else where the air flows through it. That's really the only other thing I can think of that might cause bad heating. Somehow I also kind of doubt that situation as well. I'll have to check the temp of both the hoses tomorrow and try to purge any trapped air from the system.

Hope you get yours figured out, cause I know how much it sucks driving around with warm air instead of heat. Thought about using an electric defroster you can get at wal-mart, but I really want to fix this problem, not just cover it up.

What is Mod versus OEM tech:

You could have the most radical XJ ever, but if the issue is obviously an OEM system NOT being effected by your mods, then it belongs in OEM.

If your vehicle is lifted, and you have steering/suspension issues, that would belong in Mod because the modifications have to be part of the equation.

Well I would start by removing the hoses and checking to make sure there isn't anything plugging them up as well if your saying you recently flushed the core with clr. I would try back flushing the core and getting any junk out of there and make sure where the hoses plug into the pump and t stat housing are free and clear as well.

If you saying the top hose is nice and hot and the bottom is somewhat warm when you have the heat operating that means that not enough coolant is getting through there to keep the temp up, so there must be a plug somewhere in the mix.

Good Luck.

Nothing is plugged. All hoses have ALREADY been taken off and cleaned. I can blow air right through the heater core hoses. Tstat housing is clean.

Wouldnt the different temp.s in the hoses mean the HEAT is going SOMEWHERE? Heat going in to core.. less heat coming out of the core..Maybe Im wrong maybe you could go run your jeep and tell me if they are supposed to be the same temp?? I was told this by a master HVAC tech.. but he doesn't have the time to diagnose my jeep completely. I already flushed, back flushed the core. Like i Said... I am positive its not clogged!!

Im going to try "HeaterTreater". I have narrowed it down to either the cable for the blend door or a broken blend door axle.

Thanks for the help...

I also thought that the temp difference would mean it would be working. Yet, if the coolant only passes slowly, it will rob all the heat only leaving a little heat to transfer to the air. Then if it passed quickly it would keep the heater core hot, heating the air instead of just warming it.

I just flushed mine out yesterday took 5 min and no need to burp it really.. It just Kinda filled itself right back up and I added a little extra coolant to the over flow.

Remove the actuator at the bottom of the box on the passenger side and see if you can move it freely by hand. Some foam might have blown loose in there and is fouling up your door.