So I've been suspecting a failure in my shared muffler for a while, either a leak or internal failure. I still haven't pulled it down to look at it out of the car, or had a shop use a sniffer to test for leaks, but hopefully that'll happen soon.

Anyway, I keep an eye on the local junkyard for anytime x308's come in, and recently a 99 XJR came in, which I thought would be an easy direct swap. On my car, it has flex joints between the cats and shared muffler, while this one had no flex joints between the cats and muffler. At first I thought it was a hackjob fix where someone put an xj8 muffler in as a replacement, but it was the correct part number - NNE6757AA for the one at the junkyard, which checked out as being valid for S/C cars.

Does anyone know why the difference? I'd prefer to keep what's on my car now (hopefully it's just a hole that can be welded back up) but if that junkyard one is still fine it would be nice to grab while it's there, since an XJR may come through that junkyard maybe once a year.

 

If I remember right, the flex joints were standard only on the Vanden Plas models (for "increased refinement").

 

Hi gents,

I can't tell what's the reason behind having two official setups (with and w/o flex coupling), but my MY2000 XJR has the flex coupling as standard.
I can't imagine any reason for having an exhaust system without any decoupling from the powertrain. This most likely will increase the risk to damage the mounting points of the cat converters as of the manifolds too (and exhaust brackets). And there will be more noise/vibration from the engine transferred to the chassis via the exhaust mount points as well...
When both of my flex couplings failed a few months ago, I hacksawed them and welded in two universal flex couplings with suitable pipe diameters which I got off eB**.
No big deal at all, just a little time consuming since you have to tailor the universal couplings to meet the old flange (to cat converter) and the muffler pipe correctly. An angle grinder and a little patience did the job.
I think that's the route you should go, as your cat converter version is flanged at its downstream outlet, whereas the non-flex-coupling cat's aren't apparently.

Cheers, Alexander
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By the way - what makes you suspect the shared muffler being defect? What issues do you experience?

 

I felt the same way that the exhaust should have flex joints to accommodate for engine movement etc. The one on the junkyard XJR is actually also flanged, contrary to the Jaguar parts diagram which shows sleeved joints on the non-flex-joint exhaust. Maybe the sleeved joints are only on the N/A cars.

I've been getting a rattle at load under certain RPM's - this has now expanded to a rattle at any RPM under load, to the points where I can cause it while gently revving when parked. Isolated the noise using both chassis gauges and vacuum tube to the ear to the shared muffler, towards the back of it. Removing other mufflers didn't get rid of the noise, and the cats didn't make a rattle with the chassis mics on them. More details in this thread https://www.jaguarforums.com/forum/x...t-load-194089/

I was thinking it may be failed flex joints as well, so I crawled around underneath with a hose to my ear and listened around for the noise - it was distinctly towards the back of the shared muffler, not noticeable around the flex joints.

 

Hmm, my XJ8 has no flex couplings. Didn't have any before or after. My XJ-S V12 doesn't have any either. Don't see any need for them. The engine doesn't move enough when reved to justify any flexibikity. If it was a FWD transverse layout, sure, it would need something flexy like but as a standard front engine RWD, there is no need for flexpipes, apart for making them fail more often resulting in higher sales of exhaust parts...

 

I remembered wrong, both the Vanden Plas and XJRs got the exhaust flex coupling, along with an extra attachment on the crossbrace.

 

Sorry to go offtopic, where was that info taken from?

 

That's from a hard copy of this PDF (page 48): http://www.jagrepair.com/images/Elec...jm18151280.pdf

 

That PDF is really handy to have, stashing that away in my saved jag files.

Guess I'll be going back to the junkyard for that exhaust then, I checked my muffler today and I'm suspecting internal failure, I didn't see any obvious holes, but more importantly I could cause a rattle by knocking on it with my hand.

Though I guess I could delete that muffler and replace with an H-pipe...

 

X pipe is the better choice. They don't differ much in power (H vs. X) but the X allows for smoother exhaust pulses making the sound a little fruitier.

 

Fantastic, going to geek out over that for the next few hours

 

I have seen both XJRs and VDPs with the flex joints and IIRC I have also seen them both without. I thought there was a change around 2001 but what do I know?!
I kept/added/replaced the stock flex pipes with aftermarket 2.25'' flex pipes when I built my system, easier than fixing a leaky/broken manifold after I inevitably scrape on someones driveway