2001 XJ Heater issue


New member
Need any help available. Here's what I know so far.

1. Heat blows cold
2. Blend door and the electric box that changes blend door is working. (More info below)
3. I removed heater hoses up near water pump and flushed in both directions with good flow.
4. I removed only the exit hose from core and cranked engine for a moment and had good HOT water flow coming out of core.
5. At one point, after flushing, I started to get heat but it only lasted for a day or two.
6. While I had heat, I removed the blend door controller and verified it works and when I manually turned the blend handle the door changed the air coming out of the vent from cold to hot.
7. While I had heat, I verified the cold/hot dash switch & the blend door were working. Air coming out of vent changed from cold to hot.
8. When I have the heater on, it sounds like my A/C compressor engages from time to time. It's identical to the way the compressor kicks in when the A/C is on. The engine idle changes and I swear it's the same. (For some reason I haven't checked under the hood for this yet, but will today)
9. Im hearing a sound in my upper dash that resembles a ticking clock. It somewhat sounds like a plastic gear that's slipping or teeth broken as it turns but....is there anything like that for the heater in that area? I guess it could be an unrelated engine tick that I've never noticed but sound like in upper dash near middle

Please tell me someone has an idea? Thanks in advance for any info or suggestions.
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New member
Yes. That's what the reason was. Found this after posting. Thanks for reply.

I'm going to backlash cooling system but not sure which coolant is better. Green, orange, G05.........


New member
Green is the coolant you want to use. Sounds like it might be time to pull the heater core. If you had heat after flushing it sounds like there may be some blockage. I just did the heater core on a 99 and it is nowhere as hard as everyone makes it sound. There is a lot of part removal but it is not a difficult job.


New member
I went to O'Reillys to get what I needed to flush again. Oddly, after months of no heat, I felt heat coming out of the vent on the way to the store? It wasn't hot hot but warmer than usual. I went ahead and back flushed my system and hadn't yet heard what color coolant to get, so I went with Zerex G05 per several post online. It's basically clear coolant and not cheap $$$.

After flushing for a while and draining the radiator, I have full heat. Very hot but I'm not confident how long it will last.

I had a lot of red rusty water come out of the heater core when back flushed but not sure that will mean anything in the future.


New member
Before I did the heater core I flushed until I got no more rust and then I found a wet floor. At least in my case the rust is what held the coolant in.


Twisted Up
NAXJA Member
Sounds like it's time for a heater core. Go ahead and do the evaporator while you're in there too. It's not that bad of a job, just time consuming especially if you're working solo.

I've done a few of them, and will be doing one this coming weekend actually in Hartsville SC at Ghost's shop. If you're free on Saturday, you should stop by. At the very least you can see what's involved in the process. Not sure where in NC you're located.