Recently I noticed that my my car started blowing cold air when it should be blowing hot air when the car is fully warmed up. I noticed that sometimes when I restart the car or turn the heat off and back on again that it starts to work. So far it's just a bit annoying but with the chicago winter in full swing I'm scared to think that one day it might just get stuck on cold.

Any ideas what it might be or where to start troubleshooting?

 

Air locks in coolant and electric heater coolant pump.

It's almost March anyways

Now that you've had the diff down, do you think there is any way to sneak it out by judicious removal of parts?

 

Had the came problem.

Two things: 1. Coolant air lock and coolant level and 2. also the water pump -- is it fully operational or is it one of those early models with hairline cracks at the impeller? Mine was and replacing it made a difference

 

I say the heater control pump

 

Heater pump motor most likely. lots of hot water hoses and no air locks. Check the heater hose coming and going from the heater pump. if hot its ok but if cold hoses that is your problem. Had it happen twice on my 96 XJ6.
A note because lots of cost to replace. I took mine to an auto electric repair shop and they put in new brushes and away it went .
Less than twenty bucks. Good luck.

 

Where is the heater pump located?

 

Driver side in engine compartment - Look at this JPEG file:

https://www.dropbox.com/s/sik7krcagb...Location.jpg?m

Shows location and photo of aux heater pump.

Jim Lombardi

 

Here are 2 photos showing the aux heater pump (the top of its mounting bracket) in the engine compartment:

https://www.dropbox.com/s/icw9gwr3iw...hoto%201.JPG?m

https://www.dropbox.com/s/cdnilcxuqo...hoto%202.JPG?m

Jim Lombardi

 

The heater control pump will have a small vibrate with the car on. Also, the heater control valve located next to it could also be the reason. Both can easily be done yourself. As a matter of fact, you can get these used of ebay for cheap.

 

Adam
I also had heater issues with our 2001 XJ8.
We were not getting any heat, but when I turn the temp up to highest setting and raise the rpms to almost 4000, we start to get some heat.

Then I raise the heat up very high temps (80 to 90 degrees) with the Auto temp mode, there is nothing comes out of the upper face vents and it seems to want to go the defrost vents on top of dash near front windshield.

When I put the temp down below 65 degrees with the Auto temp mode, I get A/C blowing hard thru the upper face vents.

We had a clogged heating system. The clogged condition caused damage to the aux water pump and the climate control panel.
The diode in the aux water pump motor was damaged and we replaced the aux water pump with a used one we purchase on the internet.

Climate control panel auto button stopped functioning and was replaced the climate conrol panel with a used one.
One-way valves and rest of the system had to be unclogged. It had to be done twice before it functioned normally after test drives.

I tried to get information on the damaged diode from an internet electrical parts company and local electric repair shop without any success.

diode - Response from Digi-Key Corporation:
The number listed on the part is 1E0E, the 0 (number zero) in the part number could be an O (alpha).
Without knowing the specifications of the part, we are not able to look for a possible substitute. If you are able to get the specifications for the part then we will be able to assist you further.

The following is information I collected during the extended time of our heating issues. JPEG files listed in this post are on my dropbox account - click on the image when the dropbox webpage opens to get a sharper view.

XJ X308 Water (Heater) Control Valve - Photos of 1998 to 2003 HVAC Heater Control Valve - part# MNA6711AC:
https://www.dropbox.com/s/zsz2g0zo4z...%20Valve.jpg?m

XJ X308 Heater hose with valve - photos (Heating Flow Diagram showing most of the heating hoses, aux water pump and heater control valve connections):
https://www.dropbox.com/s/0vn3eh8h6o...20photos.jpg?m

XJ (X308) Heating System Components View & List.pdf - Extract from JTIS that gives a description of how the heating system operates, also includes part numbers & diagram from JEPC catalog (dropbox.com seems to be having a problem displaying the PDF file pages, so use the download button and choose direct download menu option for the PDF files, then choose the menu option open):
https://www.dropbox.com/s/71ui8mxn5f...6%20List.pdf?m

The next 2 JPEG files were created from forum member Gus website japrepair.com that gives a DIY on the repairing the aux water pump (Photos of internal parts of pump):

XJ (X308) Heater Pump Motor Armature Brush Repair 1
https://www.dropbox.com/s/sg5bufj12t...pair%201.jpg?m

XJ (X308) Heater Pump Motor Armature Brush Repair 2
https://www.dropbox.com/s/dlum1453td...pair%202.jpg?m

Next 2 PDF files are Technical Service Bulletins on Heating issues. .

412-07 Insufficient Heat from Heater.pdf
https://www.dropbox.com/s/v8be6a1tjg...20Heater.pdf?m

303-11Am Poor Heater.pdf
https://www.dropbox.com/s/950utf1894...20Heater.pdf?m

Two Forum members responses to these issues:
https://www.dropbox.com/s/zjlp6gm3mr...esponses.jpg?m

Hope some of this stuff helps.

Jim Lombardi

 

How difficult is it to replace the auxilary heater water pump? How long should it take.

Jagpg
sanchezrpg@yahoo.com

 

Std labor is 1.5 hours to Remove/Replace aux heater pump. I bought a used one from European Automotive website for $112 delivered (6 months ago).

Jim Lombardi

 

Hi there! I had this trouble on my '01 XJ8. It ended up being a clogged heater core. I thought it was the pump too, got a used (working) one and replaced it (not too much of a big deal, even though not the most accessible - think I got it done within an hour) but turned out my original pump was still working fine. I then turned to the core and bought a $5 kit that contained a T shape connector that allowed me to connect the garden hose to the top of it, plug one end into the hose(s) going to the core (thru firewall) and using other end of the T to contol the pressure of water (with my thumb). After a few "pressure" attempts, back flushing included, some black gook finally came out. This took me 30min. Heat was back and has been functionning beautifully since.

Cheers and good luck

 

For what it's worth, I have notice something on my 2001 XJ8.

If I set the temp at, say 82 on a cold morning the temp warms up but does not get warm quickly and never blows really warm. If I set it to HI it will blow much hotter but the fan really spins in auto.

So I turn mine to HI and adjust the fan speed down. Then when it gets to a warm temp in the cabin (pretty quickly) I turn it back to auto and the temp I want.

BTW, German cars seem to have some system to divert warm water very quickly to the heating core. I am not sure how they do this but the cabins on BMWs, Mercedes, VW I have owned all blow pretty darn warm within a minute or two. Also, Mercedes have for years used a little electric inline pump to keep warm water circulating thru the heater core when the engine is off but the key is turned to the on position. Marvelous because you don't have to keep your engine idling while waiting on someone, etc.

 

Wow, Jimlombardi it sounds like you have some experience with this problem, and thanks much for the great info. I am planning to check out my heater aux pump pretty soon. I don't seem to get a lot of heat even after the car is warmed up and warm weather is coming so I can take my time looking at it. One stupid question: is the pump easier is get to if you remove the header tank ? It looks sort of like it is underneath it. All the info is great, if I could just find the thing. An observation, it seems a few people have had clogged cooling systems probably due to mixing green and orange coolant, or the old Barr's leak issue. Fortunately, I don't have this issue.

 

I was able to replace my pump without removing anything. It's cramped around there alright, but achievable. Patience and dexterity....

 

JimmyL
My cooling system had the orange type in it when I purchased our 2001 XJR in November 2003 and I replaced the coolant with dexcool (which is the orange type) in March 2011.

I still had the clogged heating system problem. I have learned an important lesson from this, I will be turning on the Jaguar heating system at least once every month to try to make sure it does not get into the clogged condition again.

You probably will want to remove the coolant expansion tank anyway to get access to the heating hoses and the inlet/outlet of the heating matrix in order to flush the heating system.

Jim Lombardi