Rear Lower Subframe Brace - Question? Video Attached
 

I am getting this rattle noise from the rear of the car when I'm going over bumps. Sounds like exhaust hitting the body underneath but I've checked and it's definately not that. I've read loads of people have had this problem and some have found it to be the shock bushes. When I was just under my car I put a crow bar up there and noticed the sub frame moves from side to side quite easily. My question is are they supposed to have any movement in them, or are they supposed to be rock solid?

I've made 2 videos so you can see what I mean.

Cheers

how did you check the rear top exhaust mounts?

The sub bushes look ok from the first vid.

Have you checked the upper/lower shock bushes?

Sean,

Thanks for your reply about the video.

I've checked the lower shock bushes and they are rock solid, the exhaust i just grabbed and tried shaking it but wasn't moving at all. don't know how to check the upper shock bush :icon_sad:

The exhaust has locating dowels that slot into bushed clamps at the top of the axle assembly, if they're worn its generally these bushes that need replacing.

Grabbing the chrome end of the exhaust can't check them because this part again is held by a bushed bracket that's bolted to the chassis, under the rear bumper brackets (Jaguar favorite, bracket on bracket)...

Have you read up on exchanging the top exhaust mounts?

No I haven't but I will now ;-)

I'm convinced it's a bush of some kind, eg, shocks lower/upper, exhaust rubbers, A-Frame etc etc, .... It sounds like it's right at the back somewhere like inside the boot. Just for my own sake, I removed everything out of the boot just to be sure, but hence the knocking is still there. I had 2 x universal joints (outer) that was gone so I've replaced all 4 now both sides of the half shafts so I know it's not them anymore, ... Eliminating parts but want to make sure I finally get to the part that's causing it, .. This is a nightmare!!

Hi Dave,

If the rattle when you go over bumps sounds like its coming from just behind the rear seat, a very common suspect is deterioration of the upper shock isolator bushes, Parts 13 and 14 in the diagram below:

http://www.jaguarclassicparts.com/il...ges/sh6541.jpg


The bushes are made of foam rubber and when they deteriorate, they allow the spacer tube on the shock shaft (Part 17) to rattle or knock against the inside of the hole in the upper mounting plate (Part 6), or one or both of the upper washers (Parts 8 & 15) to rattle against the mouning plate.

If you decide to replace these bushes, you should also replace the big foam rubber spring isolator "donut" bushings, Part 5, which compress and harden over time. Coat all the rubber bushes and every mating surface of every other part (washers, spring ends, spring seats, packers/spacers, etc.) with lithium-based grease or copper anti-sieze or you will have a dry squeak over bumps instead of the rattle you have now. Don't use petroleum-based grease because it can accelerate the deterioration of the foam rubber bushes.

I'm glad to hear the U-joints are doing well, and I'm still watching for one of those made-in-England "Mother of All Pullers" that you found! :)

Cheers,

Don

Don,

Many thanks for your reply. I was convinced it was the upper shock bushes but I guess I was just hoping it was something easier to do as I've looked up on how to change these and according to the write up, you have to remove just about everything like the A-Frame just to get to the 4 nuts holding the top base of the shocks to remove them. The only reason I've had a lot of patients with this Jag is because it's had a brand new engine fitted in 2006 by Jaguars and it's only done about 30k so it runs like new. It also cost the previous owner £5600 to have fitted.

After I've sorted out this knocking noise I've got to improve the mpg and I'm pretty sure it's the MAF at fault as it's only doing around 20mpg on a steady run! Reason why I think it's the MAF is because it had a bodge it and scarper CAI fitted and it run like a pig, until I put the original air box back on. The previous keeper also made the air flow shorter by cutting off the tube on the air intake main pipe!!

As for the pulley, ... You'll never find one like this mate, but if you ever want to borrow it, your more than welcome ;-) ... Have no use for it now lol.