I just bought my first 99 xj. It's great! I'll write a nice little intro to it later. First I need to fix the heat problem.

The PO told me it was the heater core that needed replaced. I hope not. He even gave me a brand new one to replace it with. I simply want to make sure it needs to be replaced first. I didn't see any steam forming on the windshield while I drove it home and had the fan on (this is something I read would be a dead giveaway that the core has failed). Heat seemed to be coming out a bit when I had it on the AC settings.

I'm going to flush the core with air today to see what happens. Other than that, is there any positive way of making sure the core has failed prior to ripping apart the dash?

 

I haven't tried it with air, but this is a good way to go...this also restored heat for me.


I think my core is still bad because I can smell coolant sometimes on startup if I have the vents on, and I do lose coolant mysteriously over time, although I haven't noticed it yet this year. Does your heat work at all?

 

If your smelling or leaking coolant out the condensation hole its bad....If there's no heat coming out of vents with the air its most likely plugged up.

 

You might be able to run a borescope into the heater box to look around for coolant or stains on the core.

Might not be definitive but it would be good to know.

 

What does your temp gauge read while going down the highway? And at idle? Do you have heat at idle but not when you drive down the highway? Depending your answers, might be your tstat. Just had this problem.

 

Does the coolant need to be drained before removing the heater core hoses to do the backflushing?

 

no

 

No, but there will be some coolant that comes out when you flush it out. Dont drain the antifreeze on the ground! Dispose of it properly plz.

Once the water stops coming out green you can flush it onto the ground though.

 

I had to replace mine and I knew it was busted because:

1) The windshield would fog up with grime in the winter when the defrost was on
2) It smelled like antifreeze anytime you had the HVAC on.
3) I could see coolant steam coming out from the vents sometimes.
4) I could leave the heat running full blast for 20 minutes straight and it wouldn't get any hotter than 55.

P.S. - Changing it out sucks...big time.

 

Nobody can tell you that on this forum or any other.


The best anybody can do is give you a high probability.


There are two ways the heater core can be toast:

1. It's leaking.
2. It's plugged beyond recovery.

The symptoms are different for each.



If it's plugged, you won't get steam or the smell of coolant or any heat out of it. You won't get anything at all.


If it's leaking, you'll probably get all three.

If it's leaking, don't bother flushing it. Replace it.

If it's plugged, you might save it with a flush. It's worth trying.

 

If the guy gave you a new one, did he by-pass the old one?

Are both hoses hooked to the inside? On the firewall of the engine compartment?

Depending where you live, this might not be so bad.

 

I am going to back flush mine. Someone posted a vid above, I would try that. There was another vid I saw where someone ran CLR in the heater core and then flushed with water.

If its leaking into the cab, you can smell coolant, your windows fog up, floor is wet, you need to replace yours.

 

Did you see the sequel where he had to pull the dash to replace the heater core after CLR ate holes in the heater core?

 

I did not, is that ericthecarguy one? He was doing a Grand Cherokee on the one I was watching. I was thinking use vinegar since it is a little less aggressive. The clr seems like a good idea but most of that **** isn't good for copper...

 

Auto parts stores use to carry a two part flush kit, one part was fundamentally the same as (Dap) wood bleach (Oxalic Acid) the second part of the kit was a neutralizer similar to Arm & Hammer Super Washing Soda, (not regular baking soda, used for cooking, etc.)

CLR ... Directions show to not use on copper, brass , aluminum, plastic surfaces, etc. The directions don't indicate for what reason, whether cosmetic or otherwise. Show it is good for dissolving calcium / lime deposits and surface rust stains.

There is no neutralizer for CLR that I know of other than plain water. Some people have reported problems using it ... perhaps because it was not completely rinsed out of their cooling system.

Anti-freeze doesn't normally mix well with flushing agents, if not completely flushed out may compromise the coolant and cooling system.