www.jec.org.uk

I've been trying to track this noise for a while now. I've replaced the anti-roll bar drop link bushings, top ball joint, top wishbone bushes, wheel bearings and swapped the dampers over. The only things left are the bottom ball-joint and wishbone bushes but I can't feel any play in any joints and I don't really want to drop the sub-frame unless really necessary. Has anyone else cured a mystery knocking (over holes in road)?
I'm planning a long trip this coming year and I really don't want to have to worry that something major is about to fail!
Pop

Another place you havent mentioned is the front subframe mount each side. When I replaced my front subframe bushes 3 yrs ago I didn't fully tighten the (10mm dia I think) bolt and nyloc nut. Before that it was driving me crackers knocking occaisionally over and just after top of bumps. I went round everywhere too looking for a knock and only found it late one night at 3am under the car with a crowbar for an hour systematicaly trying various forces on the suspension. Very tight it should be 5 mega foot tonnes or something. It might be that maybe?

Good point Mark, I have glanced at it in the past and the rubber appeared to be ok, but I will have a more detailed examination of the area assisted by my faithful companion Mr Prybar. However, I absolutely refuse to have at it at 3 in the morning.
Pop

I have recently stripped down a front subframe and found that what appeared to be an intact spring was in fact broken - just above the final turn as it embedded into the groove of the spring pan. If all ball joints and various bushes are intact, this may be worth considering.
Robin

Pop – As I sure you appreciate could be anything. Have you tried the obvious like worn top shock-absorber mounts (they really do make a clunk and knock over bumps)? Also have you tried the steering rack mounts they can also give rise to your symptoms. Recently did mine and noticed a real improvement. Got to be worth a look.

See that JWM has gone walk about again!

Nick

Hi Pop,

Not sure if you have traced and fixed your knocking problem, but my car also developed a heavy thump/knock when the front left wheel descended from speed bumps or went into a pot hole. It turned out to be the rear gearbox mount allowing the gearbox to touch the transmission tunnel. My local Jag specialist knew exactly what it was when he drove the car and replaced the mount for a very competitive price. The parts for the mount are not expensive and not difficult to fit as long as you can support the gearbox while you change them.

regards,
Glenn.

I've just had a MOT done. I mentioned to my mechanic my concerns so he gave everything a damn good going over while it was up on the lift. No play in anything, nothing rubbing or moving or worn. Despite his best intentions to find something wrong it passed the MOT with flying colours without even any advisary notes. He did say with gritted teeth that he is determined to find something wrong one with the damn car one day!

Still made a knocking noise on the way home though
Pop

Just another thought occurs, due to my recent endeavours - mine was making a similar noise on startup and over speed bumps - tracked it down to the rear exhaust boxes. Theres not a lot of clearance there and sometimes theres enough play to let them strike the underside creating a knocking sound.

My 96 Celebration has developed a knocking sound similar to what has been mentioned already but on the drivers side.It has been into the garage for a service and they have said that it appears to be the top bush on the shock absorber.Its going in tomorrow to be have both sides replaced so i will post if this cures the problem or not.

Further to my last post the replacement of the bushes on top of the shock absorbers has cured the problem.

I replaced the anti roll bar bushes today. I had originally dismissed them as they looked ok with no metal to metal contact. However, you may be able to see from the photo that the rubber had perished in the centre of the bush, it had turned to hard, brittle stuff (New bush shown alongside).
A short test drive seemed to show no thumps, but I will wait until I've done a longer journey before claiming success. I replaced the other side as well, but that one was in much better condition.
Pop

http://i11.photobucket.com/albums/a183/ ... 5Small.jpg

Pop
Judging by your exhaust system I reckon those bushes were good for at least another 6000 miles
Regards
DH Dove

Update, the knock/thump is still there
Pop

Pop
As per Grahams post, have you replaced the front shocker mount bush assys. (top) ? These come as a kit and can make a huge difference, also difficult to diagnose in situ. (with weight on).
There is an assortment of fibre washers, rubber washers and well, just washers!!!
This (relatively) cheap fix sorted out all sorts of bangs and knocks on my 3.6
Best Wishes
DH Dove