Now it will not start at all. It has to be the alternator. Though that doesn't explain why it wouldn't go into gear, or the thunk.

 

Is the battery dead -- or is it cranking and not starting?

Where did the rebuilt pump for the steering come from? Many of the rebuilt pumps are questionable.


These Jaguars can do strange things when the volts get low -- but you are correct .. the thunk is a worry.


On another thread about the alternator for the XJ8 -- the part was listed and coming from Amazon at a very good price for the correct rebuilt unit.

 

The battery has probably been slowly worn down by the short journeys, these cars need a lot of power to start & run the electrics.

 

I am coming here to update in case anyone stumbles across this thread. It turned out to be a bad alternator screaming, mimicking a power steering sound. The thunk is still not explained.

 

Hope it was low voltage .... everything is computer controlled and does not like low voltage

 

Alternator? I thought it might be. Keep an eye on your battery now unless you replaced it with the alternator. Very often a bad or failing alternator can take out or shorten the life of a good battery; at least that has been my experience.

 

The thunk can be a few things, go to a trusted service shop and have them put it on the rack and check that lug nuts are tight, tie rod ends, ball joints, wheel bearing, bushings (especially the torsion bar), rack mounts and pads & rotors (a loose caliper is doubtful, but possible). All very simple items to check for a proper shop (and should do it for free to try to get the work) or a knowledgeable do it yourselfer. I've rebuilt my whole front end myself (except pressing the bearings) and built the tools to do some of the work.
Not to scare you, but for the wheel bearings I had a clunk when I first got mine that the previous owner had broken the race somehow? Found mine turning also and it clicked after it clunked, going straight was fine. The clunk was somewhat loud, but slight.
Just an fyi, ...on a Jag its a single pressed in piece (about $60+) that needs to have the spindle removed (not that hard) and be pressed by a shop with a minimum 20 ton press (no Harbor Freight crap). To check it, grab the tire at the top inside the well and pull and release with force, ...then push and release with force from the top outside of the tire and listen for a clunking both times. This can be done with the car on the ground (somewhat hard) or preferably easier by just lifting the wheel slightly off the ground. You should be able to see/hear the rim move and the car stay still if its that.