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Heat is not hot anymore. At the end of my rope!

M

MattS

NAXJA Forum User
Location
Danville, VA
My situation is that my 99 XJ was overheating and had the radiator flushed and had multiple issues after doing so. I I was still overheating, blew a lower hose and had no heat. I know, I could have done it myself, but I didn't and I am paying for it. I left it with someone who checked out Jeep and said he didn't see any signs of an engine problem, seal leaks, etc. so he thought that the old radiator must be clogged due to the flush and together we decided to replace it. Also put in a 180* t-stat for good measure. I learned quickly that the inside heat isn't as hot with the new t-stat and started to discover that it would ony blow warm air while on the move. At idle, it was barely luke warm. Now this morning, I only get the luke warm air. I guess I am lucky in that it was warm enough to melt the frost on the windshield, but it will be rough when there is ice on there. I'm at a loss and I've already pumped more money into this than I should have. I'm worried that my heater core is shot.
 
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Back to the basics. What is the temperature (via temp gauge in the dash) that your engine is RUNNING at when hot? That is the first and most important thing to verify. If the temp is between 200-210, the problem isn't the engine temperature, it's a problem transferring the engine heat into the cab.

Have you tried flushing your heater core yet? Always a first line strategy with heat problems as well.

For your stock 99, I recommend at JEEP 195 degree thermostat, although I do not believe your 180 stat to be your problem. Having a 180 stat doesn't mean that your engine RUNS at 180 degrees.
 
The gauge stays in that section just under the 210 mark. I call that 180ish, correct me if I am wrong though. For what it's worth, it worked ok for a couple of weeks.
 
If it's just under the 210, I think the temp is slightly higher than 180, probably closer to 200 but that's splitting hairs. Your engine temp is pretty much where it should be.

If it were mine, I would first try to verify that your problem isn't with the HVAC system (believe they call it a blend door) that allows heat into the cab. If that seems to be working properly, I'd try flushing the heater core.
 
i agree with birchlakexj. start w/ flushing out your heater core, and maybe replace your heater hoses.i think teamcherokee.com has oem ones for sale but check around on prices. also did you actually flush your coolings system or did you just drain and refill your radiator. there are a number of shops that have coolant system flushes available where it will flush your system entirely while its running by allowing the system to cycle completely where a drain and refill of your radiator doesn't do much more than change out 50% ish of your coolant.
 
YUCK!!!

I don't smell anything out of the ordinary when the heat is on. I guess I'm lucky in that sense. At least she runs for the time being.
 
I just had to "blow" my heater core out. It was clogged with some nasty junk.

I took the heater hoses off the thermostat housing and filled the upper one up with water. I then used a quick disconnect, the one the goes on the tool, and put it in the upper hose and clamped it down. It took about 100 psi to blow the junk out the lower heater hose. I went through the water fill and blow procedure until the water coming out the lower hose was clear.

I now have good heat.

If yours is clogged and you crack it because it builds up too much pressure it is not my fault!
 
I'd say heater control valve. Follow the small (~1") line back from the thermostat housing, and you should run into the thing. It sometimes "freezes" or gets clogged instead of "blowing out" and leaking.

(NB: I know later models did away with the thing, I just don't recall the cut-off. It's possible you may not have one.)

If that's the case, then it may be a plenum or blend door issue - for which you have to tear the dashboard to bits. However, it usually isn't, if you have the heater control valve in place.

It's possible to eliminate the thing, but your aircon would have to work a little harder if you do.
 
I vote heater core. That was my only issue while I was over thinking the issue. The heater core was plugged as all get out...low pressure water wasn't cutting it. Blast it!
 
If you plan to "blast" your heater core don't be suprised if it begins to leak in not too long...sort of like flushing an old radiator. How many of you have had a radiator that you flushed that started leaking shortly after?

Your best bet would to use an open garden hose and flush/backflush the heater core gently. No pressure beyond with a garden hose with no attachment on the end will give.

Although I doubt that is your problem if all of a sudden you do not have heat after blowing a radiator hose and replacing the thermostat. What brand thermostat are you using?
 
bhansen99xj said:
I vote heater core. That was my only issue while I was over thinking the issue. The heater core was plugged as all get out...low pressure water wasn't cutting it. Blast it!
Click to expand...

My vote is a regular 195* Stant or OEM t-stat AND core flush with the hose. After which, get the engine to operating temp and give the heater hoses a feel. If they're warm/hot it should be all good.

There's got to be a reason the coolant isn't passing through the core. With the exclusion of a FUBAR'd blend door it's pretty simple. Hot water through core+operating fan+air blending=heat.

...and be sure your belt is routed correctly to send coolant in the right direction.
 
Another vote for OEM Jeep or Stant thermostats.

I've used AutoZone thermostats before and with one I didn't have really any heat, kind of warm but not acceptable. Strange thing is that the motor kept a good temp. But switching to a Stant thermostat fixed it, and now I'm running an OEM.
 
He should be able to see the lever move on the heater box under the passenger's dash right? At least you can see it move in my 95 if you look down there. Although I don't think that's a clear indication that the blend doors are actually moving.

Or are the 97+ blend doors not cable actuated anymore?
 
Nope, 97+ is all vacuum operated.
 
THis whole heater thing is a common story. Like I said on the other posts, there is a special slot on the thermostat gasket. It seems like if that slot wasn't there due to a generic gasket or being put on wrong, that the coolant wouldn't flow to the heater. And again, the question: Are the heater hoses hot? If they both are, you have flow through the heater core. You talk about warmer air on the move....Is the blower working?
 
Yes the blower is working. The temp inside isn't as hot as before, but I'm chalking that up to the 180* t-stat. I am hesitant about flushing the heater core. My gut tells me that its on its last leg.
 
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