Hey guys.

I'm certain that I need to replace the heater core in my XJ, it's bad enough that you can see vapor coming in to the cabin through the vents when it's running. It has a developed a significant coolant leak, it drips down mostly through where the passenger side control arm attaches. Is this likely coming from the heater core leak, or do you think there's another leak in the system.

I'm willing to try to tackle the heater core, but if there are other leaks, I'm not sure I really want to try to fix this.

 

99% sure it's your heater core.

Since you'll have the dash apart you might want to also consider;
- Replacing the Evaporator Core.
- Rebuilding the HVAC box.

 

Heater core.

 

Before deciding that it's the h/c it could be the hoses not tight enough. Try this. Loosen both hoses and pull them away from the firewall some to where you can see a bit of the heater core tubes and then tighten them. The hoses have a tendency to stick to the tubes so twist each hose to loosen their grip on the tubes before pulling on them.

 

I just got done doing the heater core replacement. Try what ezearl said first, tighten the heater hoses on the firewall.

Also, you said it's leaking on the control arm on the passenger side...there isn't any coolant leaking inside the Jeep on the passenger side floorboard? That's where mine was leaking.

 

Would loose hoses result in the vapors coming in through the vents?

 

No coolant under the carpet. Inside there is just coolant vapor coming in through the vents.

There is a significant leak externally, and wherever it is originating from it can seen dripping out around where the passenger side control arm connects.

 

If the hoses are stuck trying to reposition them, be careful. Ive seen tubes snapped off doing that.

It could, yes. Any coolant getting past the clamps and into the box is no different than a leaking core.

 

Could you possibly take a pic and circle where I should be looking???

 

Heater hose to core

 

That's this spot, right? I took this pic with it running and it was dripping away. Looks ok there, yeah?

 

Or:


See how in your pic the hoses are tight against the firewall? Coolant could leak into the cab without being seen. Loosen the hoses. Back them off away from the firewall and then tighten them. Not saying it's your problem but I've seen it happen a lot over the years.

 

that top heater hose looks too close to the firewall. I just replaced my heater core and thought I had a leak. EZEARL said to pull the hose back a bit so you can see some of the heater core pipe and then tighten it down again. I didn't have a leak after that. Worth checking but might not be the answer.

I don't have a lot of experience, but I don't know how a heater core could be leaking and not dripping from the bottom of your HVAC box. Somebody else probably knows more about this.

 

I guess I will find out shortly, but how much heater core pipe should I have to work with sticking through the firewall?

 

You've got plenty. All you need is to get the hoses away from the firewall leaving a small gap to where you can see down in there.. BUT as fb97xj1said above "If the hoses are stuck trying to reposition them, be careful. I've seen tubes snapped off doing that." I've never had it happen but can see how it could.