I have a 99 XJR- 109K, runs great and drives very well, I have noticed a "bumping sound" in the back of the car. It sounds much like the rear passenger door is not closed firmly whenever I go over bumps in the road nothing in the trunk, and door shuts firmly. I have noticed it getting a little worse over the last 500 miles. I can't feel any reaction thru the steering, it just sounds like the back door is not all the way closed. Sure could use ideas and things to check. tks

 

Check the exhaust hangers above the rear suspension. The clearances are tight for the pipe so if the hangers break or tear you hear it

 

+1 exhaust hangers: particularly noisy in cold weather (I hit them with silicone spray once a month), once it gets over 90*F, they get quieter (or I am getting deafer).

Loose battery or junk in the trunk can get noisy (especially if your spare tie down is missing or loose).

Or the lower shock mounts have deteriorated badly.

 

+2 on exhaust hangers.

Also, the rear shock upper isolator bushes can deteriorate over time (Parts 13 & 14 in the diagram below, or parts 21 & 22 if you have the adaptive damping). If these rubber bushes disintegrate, the washers on the shock shaft can bang around on the upper mounting plate, Part 6. These upper shock mounts are positioned just behind the outer edges of the rear seat, so when they begin to knock the sound seems to come from just inboard of the rear door latch.




Cheers,

Don

 

My '02 XJ8 had a similar noise that I had a hard time finding. Swore the noise was in the rear, checked everything, I was thinking the diff was going bad. Turned out being the front upper shock bushings. I knew they were bad so I replaced them. Voila, the rear noise went away.