Replace IRS Mount in car?

Series 3, XJ6 - Is it possible to replace IRS mounts in the car? I have just finished rebuilding calipers, replacing discs and shocks with the unit in the car when I noticed one of the passenger side mounts is cracked. I know the correct procedure is to remove the entire unit but after all this work underneath, I am not looking forward to it. Has anybody figured out a line mechanics work around?

I’ve never done so.

But I can’t see any reason that it can’t be done that way.

In a nutshell…

Do one side at a time. Loosen bolts a bit. Place floor jack under the side your working on to support the weight. Remove bolts. Lower subframe a bit with the jack. Slide old mounts out and the new ones in. Reattach bolts.

I’m on my first cuppa coffee so maybe I’m missing something.

Let’s her what others have to say

Cheers
DD

Lucky yyou, I am only alloeda half cup of weakrnrd NESTLE 1

CARL

I’ve done it without removing the cage - just dropped it enough to get the mounts in. The complication might be the exhaust. Mine didn’t give me any real problem - i just let it flex.

One thing though: when reinstalling attach one new mount to the cage and one to the frame (for each side) as described in the service manual. It’s easier to get it back in that way.

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I would add just an observation from my experience. I don’t think the mounts will slide out by lowering the IRS a small amount. The angle of the IRS mounting surface and the frame mounting surface run parallel and the IRS side of the mounts have studs instead of bolts. The one side of the IRS would have to be lowered probably 6" to 8" to clear the studs and the top mount channel in order to remove the mount straight down. I would worry that much “tweak” on the mount on the other side might not be good for it. Watch the flexible brake line and e-brake cable when you drop the left side. After saying this, I can imagine the exhaust will be a major player, mine did not have an exhaust and dropping the IRS was very easy, about an hour and my Son and Daughter-in-law to steady it as I lowered the unit with a floor jack.

Dave

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To elaborate a little bit. I had to do it in situ out of necessity because I lifted the new-to-me car on someone else’s driveway from the rear jackpoint and the cage basically fell out. Checked further and the other side was completely gone as well. Didn’t feel safe driving it as you can imagine so had to do it as quickly as possible where it sat.

I had to do both sides obviously so I had to drop the whole assembly straight down a little and replace all 4. I’m not sure if you could do one side at a time because of the tweaking @Daveak mentions. As I said before, when reinstalling put one mount in the frame and one on the cageon each side. Also I kept the mount bolts loose while lifting cage back into position so there was a tiny bit of extra play.

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Thanks for the replies, I am hoping more information will surface before I attempt anything.

That’ how I would do it:
Raise the rear and support the car on stands. Always keep a jack under the IRS.
Remove the wheels
Disconnect the exhaust joint (in the front of the IRS)
Undo the rear exhaust tips and unhook it from the hangers
Undo the mounts and you can now lower the IRS enough to change them.
As mentioned before keep an eye at the flexible brake line and handbrake cable.

PS
The IRS is front heavy, so having the jack biased to the front helps to keep it straight.

I wrote exactly the same, but didn’t get to the end. Fully agree. Put socks over the exhaust ends to protect the paint.
Oh, and I‘d disconnect the exhaust further forward at the transmission, one joint and easier.

Fully subscribing to what David wrote: getting y-pipe, front mufflers, over-axle pipes and rear mufflers lined up without disturbing the IRS is a good piece of work, so better not change what isn’t broken …

Good luck

Jochen

75 XJ6L 4.2 auto (UK spec)

Indeed.
Coming from the V12 world, it didn’t cross my mind…

I would be very inclined to try and lower the IRS & exhaust without separating, only the hangers

Think 4 to 5" would allow enough to wriggle them out

I know for a fact I can udo my exhaust manifold to cylinder head nuts in under 30min

Thanks for the replies. I finally decided why not remove it completely and do it by the book.

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After pulling the IRS to replace the mounts I realize I must have been crazy to do the discs and calipers while it was still in the car. I used a transmission jack and took it in and out by myself faster than I did one side of the brakes. Live and learn, eh?

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We keep tellin’ people. Nobody listens.

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It’s psychological more than anything…
I think it’s the Jaguar rite of passage. After that you are a man…!

I did the handbrake calipers and pads in situ once. Never ever never again.

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The time it took us to do the handbrake calipers in situ would have been sufficient for the Jaguar Le Mans crew to rebuild the car after a rollover …

Anyhow, it’s not only a matter of psychology, but also of routines: if you’re trained to do so you’ll drop the IRS cage in an hour blind folded, just as you’ll remove the hood and pull the engine from a Spitfire to get to the clutch. If you’re not skilled you’d rather be respectful of the operations necessary for such far reaching actions.

Plus, everything will go off quickly only if parts are used to movement. Things may change totally once you attempt a full removal for the first time after 40 years. Rusted bolts and seized bushings may disturb your time sheet considerably. So better not feel too bad about that extra hour …

Good luck

Jochen

75 XJ6L 4.2 auto (UK spec)