exhaust rattle!

[CliveRothwell]

The rattle occurs during warming up and has been identified as being a loose outer shroud (heat shield?) on the centre section on the NS pipe. So, the question is, assuming this is an after market system, what it the best way to cure the rattle from the loose part? Do original systems have this outer shroud?
Obviously, the rattle stops once the inner pipe has expanded enough with the heat.
Cheers
Clive

[PaulGover]

The rattle occurs during warming up and has been identified as being a loose outer shroud (heat shield?) on the centre section on the NS pipe.

I take it this is a V12.

So, the question is, assuming this is an after market system, what it the best way to cure the rattle from the loose part? Do original systems have this outer shroud?

Why assume it's after-market? The Jaguar exhaust parts are decent stainless steel, and should last quite some time. There are several heat shields around the exhaust pipes and manifolds. and I'm not too sure which you are referring to. Are you talking about the exhaust pipe that runs under the floor between the catalyst (if fitted) or downpipe (if not) and the intermediate silencer in front of the rear axle?

That pipe has double wall - inside being the actual exhaust pipe, the outside being a retaining shield, and I presume some insulation between the two, so it fits your description. My Facelift car has this, and I believe it's the original Jaguar exhaust - the only bits replaced so far in 20 years are both rear silencers, about 10 years ago.

If it's rattling, what's it rattling against? I wouldn't expect it to make much noise itself even if loose, as its full of heat insulation, and that would dampen the sound. Try to see if you can rattle it yourself. As far as I remember, the cover is made of two pieces of pressed sheet riveted together, so check if any rivets are missing.

If nothing obvious is loose, you could try putting a pipe clip around the ends, or maybe squashing the shield into an oval cross-section with the judicious application of a little force - not enough to disturb the inner pipe, maybe with a couple of mallets. Or insert some extra insulation at the ends, maybe try forcing some exhaust sealing past using an old sealing gun.

I've had various noises from the exhaust rattling against the chassis section (box section) alongside the propshaft/gearbox. Aligning the exhaust to get adequate clearance all the way to the back is a bit of a black art, and it's easy to get the pipes to hit the wall when the engine twists against its mounts under acceleration. I had this noise 'cos my engine mounts weren't seated properly.

Obviously, the rattle stops once the inner pipe has expanded enough with the heat.
Cheers
Clive

I'm not convinced that the inner pipe's expansion would cure the noise in that manner - its diameter would only increase a little. IMHO it's more likely the extra length changes the pipe's alignment and something's no longer hitting the chassis member.

[CliveRothwell]

Hi Paul

Yes, it is the intermediate box. The rattling part is the outer shroud hitting against the actual central pipe. I can't see any rivets that look out of place. I assumed that at 10800 miles it is non-genuine. I think on balance some exhaust paste may be the easiest solution. Thanks for your detailed response!

Clive