In that case, it is almost certainly the auxiliary pump. As you will have seen from the links, the small carbon brushes eventually wear out (mine went at 120k miles).
Fan behaviour is normal I think. Temperature gauge is pretty useless - it sits in the middle until the engine is dangerously hot, and Then moves into the red, at which point it is usually too late.
The oil-pressure gauge is similarly useless and is actually just an on/off switch.
Steve (the jagwrangler) does a kit called 'realgauge' - which converts those two gauges into something useful and also adds an audible alarm.


XK8 / XKR / XJ RealGauge - TheJagWrangler

 

I tested my heater pump by jumping from the +12V post to the heater fuse contact (6 inch piece of wire, 10 amp fuse removed). With the ignition off, the heater motor (if working) can be easily heard whirring away.

 

the gauge wont move until its overheated. had some trans work done on my 99 and in the process they removed the heat shield between the engine and the aux heater pump. approx. 6 mos later the aux heater pump fried. same conditions as you describe on mine where the hoses go into the fire wall one was very collapsed.

 

Worth bearing in mind for a future upgrade as it seems the standard ones are fairly poor for accuracy.

Think I might have a go at that before taking the final plunge...when the weather is a bit more clement, that is.

 

Have you tested your front fog lights, the fuse for that panel controls the heater switch above it. That was my problem anyway.

 

Hi, just joined the forum and read this thread with great interest. I've the same heater problems. Yesterday I took out the relay for the pump and ran a wire with a spade connector on each end across two of the terminals effectively making the pump run continuously (can hear it). No better, still Luke warm heater. What's the next thing to try?

 

Further to above post just read on a bit, seems previous owner replaced(who posted a thread on this site) the pump in 2012. I bought the car 2015, heater wasn't great so I replaced it! Didn't make a great deal of difference. The car was stood on a drive inactive for about 3 years before I bought it and had only done 83k miles in total. I've already used some holes rad flush but it made no difference.

 

The fuse you want is #15. If you can get your hands on a auto stethoscope and see if you can reach the pump from the top. With the fuse in and the car running and heat on touch the pump with the stethoscope and see if you can hear it running. I will attach a link on how to get to the pump.

Link JagRepair.com - Jaguar Repair Information Resource

Link JagRepair.com - Jaguar Repair Information Resource