Well the best way I can describe how warm my 'heat' is coming out right now is that it's about as warm as when you blow on your hand, i.e. not very warm. Right now I suspect the heater core, but I can't find a really nice illustrated howto. Think you could help me diagnose this problem?

All equipment currently in the heater assembly is the original equipment, so aging is a major factor.

I do not have an a/c

Bump?

Make sure the antifreeze is topped off.... And is the temp gauge looking normal and no heat coming out, or is it barely getting warm?

I don't know if he took pics and stuff, but I think FRANKZ just replaced his heater core. All I know is you're in for one heel of a time. That is definately NOT a fun job, even worse on an XJ.

I'd try disconnecting the lines and seeing if you could blow out the heater core first before diving into the R&R...

Antifreeze is good on level, it's just barely getting warm...even after several hours of driving (cheyenne and back, about 180 mi and it was still blowing lukewarm). How do I blow it out? Pics would be super helpful.

But is the temp gauge showing around 210, or not even making it up that high?

Could the valve only be partially open, only allowing a small amount of coolant to run through the core?

I think what BowtieGuy is getting at is this..........Is your engine getting up to normal operating temperature on the temp. guage??? Really important for isolating this problem to a bad componant.

If the engine isn't getting more than luke warm, your T-stat could be stuck open.

If the engine is getting to 185-210, I.E. normal operating temp. and the heater is only getting luke warm then you could have a stuck shut Heater Control Valve or just the vacuum line could have fallen off of it. Or you could have a plugged up heater core.

Pops suggested a bubble in the line, seems the problem kinda solved itself, though, and now the heater's working fine...now to find that new vacuum leak. F**king gremlin is running rampant in my jeep.

Yeah sounds like a bubble may have gotten stuck in the heater core, I have one flowing through my cooling system too. My temp gauge will go up to 210.. and then a min or so later it will drop. With temps below freezing there is quite a bit room for it to drop. I just havent taken the time to burb the system. Maybe this weekend.

There's quite a bit of vacuum noise coming from the vehicle and I can't figure out where from. It's definitely the vacuum, I know that. I now think this is the most likely candidate. Where's the vacuum line for it run?

What about the "air heater control valve"? Bout 30 bucks to fix new.

would that address the vacuum whine I've been hearing?

Dont know, but it does have a vacuum line going to it. I would check it. Come to think of it if your hearing a vacuum whine then it may be loose or a broken line?

Where would it be? Still learning the workings of the XJ

Same here, I've only had mine for about 10 days, a Cherokee newbie I guess you could say. The valve is located on the passenger side near the back of the engine compartment. Its the contraption that the two heater box hoses go into from the front of the engine.


I think there is 3 water lines attached to it as well as a single vacuum line coming from the interior side of the firewall.