Hi
I have a 1995 XJS V12. When travelling over rough ground (think poor road surface rather than speed bumps) I can hear a "boing" sound. It is not a rattle nor a knock. The sound seems to emanate from behind the rear seats on the off/driverside. I have had the interior out (https://blog.buyanypart.co.uk/think-...n-6e8d67693005) and checked the body components, exhaust and mounts but cannot seem to replicate the issue. I appreciate the almost ridiculous, 1st world nature of this question but i am also sure as owners you understand that it is irksome to have a noise that breaks the silence of the creak of leather and purr of the aircon.

 

Chris
The first thing to do is to check if the bump stops are in place. Also then check the tightness of the shock absorber mounting bolts top and bottom and check their bushes are in place. If you have those daft cowls over the UJs, either remove them or tighten them and make sure they cannot foul anything. Also check the mounting units of the cage are tight and not delaminating. Finally check the propshaft fixings and the driveshaft flange nuts that hold the shaft and the disc.
Also wheel nuts tightness, exhaust joint flanges, and check the exhaust where it goes through the cage is not fouling something.
Greg

 

Cheers Greg.. Speedy reply.. Thankyou

 

Adding to Gregs list and thinking of the "boing" yo describe.

A collapsed road spring, maybe, but the way they are mounted I would also expect a rattle form the cleats and collar????

Cradle mount "V" rubbers. Age is now against them, and they are hard to diagnose quickly. The car has 4, 2 each side.

The fact its heard/felt more under the backseat, MAYBE, if the car has one fitted, the rear sway bar "D" mount rubbers, as they are basically right under the back seat area.

I say MAYBE, coz Jaguar played with the fitment of a rear sway bar in various markets etc throughout the cars life. Some have them, some dont.

 

Gents - thanks for your thoughtful replies. Any view on the boot hinge springs on this particular genre of car? I was at a meet just now and another XJS owner (89) suggested that could be the issue

 

Specifically to Grant - the springs I can rule out as an issue as I have checked them but thank you for the suggestion

 

Chris,

I would have thought your late car would have gas struts for the boot spring/s???

Maybe not.

This is a parts drawing of the earlier tension spring arrangemey, and yes, they can "boing", hence the tie strap to stop that noise.



This is the later style.

Attachment 145548

 

Great work guys... some things for me to play with.. I am really impressed with this forum

 

and thanks for clearing the struts point up.. I feel a bit sheepish as hadn't thought before I asked

 

Another thing I thought of today whilst doing the rear brakes on the Black S Type, why I would think about your car???, OLD AGE.

The fuel tank may be "flexing", and/or have a loose baffle inside. The tank base could be contacting the car bodywork at some point.

If your car has the gas struts for the boot lid, the panel that is bolted to the body to secure the lower strut pivot, may be flexing, and since it is still under load from the struts, when closed, may be the noise.

 

Thanks to Chris for raising this and the other guys for chipping in with ideas as I have the odd rattle from the back of my '90, 3.6 coupe. Most of it seems to be trim related as I am told their is nothing amiss underneath.


So would be interested to hear what you find Chris.


Thanks to Grant for the tip on the boot spring. I only had 1 loosely fitting cable tie (No. 8 on your graphic) on mine which rattled when tapped so have added a few more to tighten things up.


One area I get an annoying rattle from over rough roads seems to be from somewhere behind the air vents just behind each rear window. Anyone ever had this and solved it?


Cheers,


LeeP

 

Yes, me, and it drove me mad as the rest of the car was rattle free after my rebuild. The air exit vents have three hinged flaps hidden inside, and the foam padding on their shutting faces crumbles, and then they click when they flap shut on bumps etc. I glued two of the three shut and removed one flap completely. Problem solved.
However getting to these flaps is hard work. It entails removing the rear side windows, the exterior chrome trims, drilling out the pop rivets that hold the inner unit in place, etc etc. A couple of pics attached.
Greg

 

Possibly the air extractor flaps, located behind the black exterior trim panels, have lost their foam cushions and thus giving a metal-to-metal rattle.

https://www.jaguarclassicparts.com/u.../air-extractor

There are similar flaps in the trunk, below the rear windscreen, rough speaking

https://www.jaguarclassicparts.com/u...xtractor-trunk

Cheers
DD

 

Greg, thanks for the very comprehensive reply (also thanks to Doug for the links to the parts diagrams). Do you or anyone else know if it is possible to reach these parts from the inside of the car to at least quieten them down a bit?


Cheers,


LeeP

 

Check the rear tranny mount

 

Not possible. As my photo showed, the extractor unit and flaps are in a cavity in the bodywork only accessible from the outside.

 

Thanks Grant. I stripped the boot/trunk out on the weekend right back to the tank but found nothing obvious and could not replicate the sound. All insulation etc seemed to be in the right place. Home who prepared the car before I bought it had the fuel tank out to find pipework internally incorrectly manufactured which they resolved but that also did not solve the problem. I will keep you posted. Thanks to all others whom responded.. Very impressive forum

 

Thanks Doug. I checked those flaps when i had the interior and boot/trunk stripped out the other day. Good shout though.. Thanks

 

Thanks BC XJS. I think the next step is to muster the energy to get into the components under the car..

 

Hi Chris

Before you start pulling your Car apart, I had exactly the Sound you describe on my Car.

Which turned out to be one of the Rear Silencers/Mufflers hitting on the Bodywork underneath.

Those Silencers are a Nightmare to line up and it did take me many attempts before I finally got it right.

One of the Chief Suspects, is where the Rear Silencer/Muffler sits up in that box like cut out just behind the rear wheel.

Make sure its held in BOTH PLACES with the Rubber Supports, which the Steel Pegs on the Rear Silencer/Muffler Pass through.

When you think you've got it right, jam a piece of wood in to the side of it, so that it doesn't touch the sides of the Cut out behind the rear Wheel:

UNTIL YOU'VE DONE ALL THE JOINTS UP!

Or when you lower the Car down. You may find the Silencer/Muffler, has mysteriously swung down into the same position that it was in before.

Its gotta at least be worth a shot before you try anything else.

It worked for me.