I have read the posts/threads regarding no heat, but I have somewhat of a unique/dumb situation. I bought a 2001 XJ8 with 78K miles . When I bought the car, everything worked including the heat. But it did have a small coolant leak, just couldn't determine where the leak was. After driving the car for awhile leak got worse and i put a bottle Of Bar's Stop Leak down the coolant reservoir. Bad move!! At first everything was fine. Then the heat went out. I had the car looked at by a mechanic Thermostat housing was bad. Had it fixed. Still no heat!! Figured I had clogged something up. Had the system flushed, all hoses removed and checked for blockages. And the Heater core was flushed with water until it was clear in both directions. Also had the AUX heater pump and Heater Control Valve removed and taken apart to inspect for blockages All Clear!! Still NO HEAT! I have disconnected the AUX Heater Pump, so that I can feel the difference when its connected and running and when it's not. It's definitely running. I can't tell how warm the hoses are by the heater core/heater control valve because it's so much engine heat in that area. But i know the hose from the AUX heat pump is Luke warm at best. All other hoses are hot. Not sure how to test Heater Control Vakve, but from what I read they don't go bad top often.


What am I missing? Is is possible I could have messed the pump up with the Bar's Leak? Only thing we haven't done is remove the Heater Core from the car. But like I said, mechanic "said" he flushed it. I get no heat when i idle the car at 3000 rpms or when I drive down the highway. I welcome any and ALL suggestions. Please chime in. I hate to just start throwing parts at it.

 

The heater control valve should be OPEN when power is NOT supplied so it should flow.

There are some plastic 'check-valves' in the hose assy behind the throttle area that you might have 'clogged' with the 'leak-stop' chemical.

You can see the valve (like little barrels) in the hose assy and they can be removed and checked. They have clamps on both sides and an ARROW marking direction of flow so be SURE to orient them back correctly.

good luck.

bob gauff

 

Just grasping at straws here, but the bars leak might have nothing to do with your problem. Maybe, and only a guess, maybe the heater control head is not working properly. You need a scan tool that would read it's parameters to tell what setting it's on. If you set it at full hot but the car doesn't see that, it won't send out heat. Something to check at least.

 

Check out this excellent thread on the climate control system. A few posts down it tells how to get fault codes to display.

https://www.jaguarforums.com/forum/x...nfo-faq-66454/

 

Motorcarman,
Thanks for responding. You said there are some check valves behind the throttle assy? I'm assuming these are separate from group of hoses that go in and out of heater control valve into the heater core? I'm not mechanically inclined, but I can lead my mechanics to the area you suggest. Would you have a diagram of the check valves or even a camera pic from your jaguar? Thanks again for your help in trying to figure this out with me!!

 

GateKeeper,
I would be inclined to go with the climate control head or possibly something else electrical....But the heat worked fine before I put the bottle down the system. I forgot to mention in my initial post. I ran the diagnostic mode on the climate control system and it has no codes.

 

The plastic 'valves' are IN the hose matrix. They are PART OF the hose assy. They are black plastic and cylindrical.

I don't know if they are ONE-WAY or just flow restrictors.

There is one in the hose from pump-to-heater valve and the other is directly above the gearbox bellhousing.

I would suspect the one in the pump-to-valve hose (MNC6742AC)

The other hose is #6 in the JEPC and is listed as 'HEATER HOSE (WITH VALVES)'

The 'valves' are NSS, they are part of the assy.

bob gauff