Has anyone any idea of where I should start looking for the fault in the stereo system. The warning tones still work, but no music. It does not bother me too much as I never sit in the back :-)

 

Obviously start with the speakers themselves.

FIRST.....MAKE SURE THAT SOMEONE HAS FOOLED WITH THE FRONT TO REAR BALANCE CONTROLS.

I doubt it's them but I'd temp. hook a known good speaker back there just to double check. Next would be wiring which can be checked with a multi-meter signaling continuity. Last, and most likely, is the rear channel output side of the head unit itself.

Any scratching or static like sounds coming from the rear speakers as you adjust the balance or volume? That's an older indicator of trouble pretty much confined to the mechanical portion of the controls and indicated an internal short caused by accumulated crap of the mechanisms themselves.

 

I checked the balance controls a couple of times, even looking at the book as I followed instructions. I have a feeling it must be at the front end, as there is not even a line hum at the speakers, no sound whatsoever.

 

You'll most likely have little to no luck finding a repair facility as we are now a replacement society. They appear regularly on eBay for between $100-150 from the salvage lots who guarantee them for fit and working condition for a short while in most cases. If you go that route make damn sure it's for a later model XJ8 with the fiber-optic connections.

A few examples:

04 07 Jaguar XJ8 Factory CD Radio 2W9318B876BK | eBay

Both pieces:

04 07 Jaguar XJ8 CD Radio Player LKQ | eBay

 

There is a known fault with the actual connections to the speaker diaphrams.

One owner has soldered new connections parallel with the existing.

I must say though that it is unlikely that both would fail at the same time.

 

As they were both out when I bought the car second hand, I will have a look to see if it is the speaker connections, as I have no idea when they went out.
I don't really notice it much, and the last owner was on the phone a lot and hadn't bothered fixing the trunk(boot) cd changer when the cassette locked up.

 

It's not a difficult job to take the two small side covers off of the CD Changer (about 1" square) at each end and manual try to work the cartridge out. You can see the spring loaded mechanism. Failing that the case is not that difficult to remove but be careful with the small box attached to the back as that's what decodes the fiber optic signals for the internal circuits.