My 02 XJ8 has a strange issue with the heater. On the hi temp setting and no A/C it will get warm, but not hot. When AC or Auto is activated, air temp goes cool, but not cold. No codes or system pass.

Heater valve, auxiliary pump, thermostat have been checked or replaced and are working to spec. Heater core has been back flushed.

Blend door issue with no codes?
Anyone have a schematic of the interior ducting?

 

I had a similar problem, but in my case it was a combination between many things.

From the list you mentioned one very important thing is missing - have you checked the solenoid under the cooling system expansion tank? Mine was stuck on close state because of limestone residues.

Another important thing - how did you check your auxiliary pump? It may sound as it works, even the motor and propeller can rotate, but in some cases the speed and RPM of the fan can be insufficient like in my case. I had to disassemble the circulation water pump and change the propeller's axis/shaft because with time it has become thinner which caused high friction and because of this - less speed of rotation. If it gets hotter if you rev the engine up, then you need to look at the aux heater pump for sure!

 

How did you check the pump? The pump on these cars do not have a direct drive to the pump housing. The pump motor will turn freely and the pump itself could be frozen with sludge or corrosion. This is what the pump looks like Jaguar XJ6 Aux heater pump

 

One of my blower motors squeaks at mid speeds which is very annoying, does anyone know if there is a way to lubricate these fans?

 

Unable to help!

 

I believe the solenoid under the coolant tank to be the heater valve which is working properly. I replaced the pump. The cool air bypass is opening and closing but I can see if the door is broken without pulling the console plus. I'm wondering if the heater core could be partially clogged?

 

I meant to say "can't" see if the door is closing all the way

 

Turned out to be a clogged heater core. The only thing that worked was straight CLR for 20 minutes. Then pulsed pressure with water hose and then various bits and pieces flowed out for over 10 minutes. I'm guessing the reason it would not blow warm on foot is the foot air blows across the lower section of the heater core which was clogged worse. I was ready to pull the dash to fix a blend door problem I didn't have. Dodged a bullit there.

Thanks to Gus and others for the replies.

Shuamanator

 

I took the liberty to look up CLR and what precautions you need to take and this is what I came up with.

CLR Frequently Asked Questions and listed under FAQ I found this.

"Can I use CLR to clean out my radiator?
No, CLR should not be used on a car radiator for two reasons. First, CLR may not be compatible with the internal metals of the radiator. Second, it could have adverse effects if the CLR is not rinsed out completely."

Although I admire your creativity and desire to find a fix I would recommend that your procedure not be recommended as a fix just yet. Improper use and flushing of the system may cause a catastrophic effect resulting in additional problems. I would recommend calling or writing CLR and see if they can elaborate on your application and the mix with antifreeze.

 

True, CLR clearly states on the bottle, not to be used on aluminum and other metals.

That being said, I have used it on my XJ8 and two other customer cars as well with no leaks so far. 1 year on one, 6 months on another, and only a couple of weeks on the XJ8.

The import part that didn't elaborate on is that each application needed a heater core replacement from being clogged anyway so worst case I was replacing the core.

In each application, I disconnected the heater core to only run CLR through the core and not the rest of the cooling system. And I'm fairly certain there was no CLR left in the core when finished.

I found out about this technique from a VW tech who uses CLR all the time on Passats that come in with clogged cores.

This has worked for me and others when all other flushes have failed.