StratfordShark

During brake refurb I discovered torn out cv boot on RHS - must have happened since last official inspection in April.

3/4" breaker and jack handle extension made hub nut removal easy. The threads at end of shaft were still covered in copper anti-seize which helped - maybe applied in factory?

Got all the allen bolts out at diff, but now things differ from Dwayne's excellent guide. He only had to lower exhaust to remove LHS shaft, but on my MY91 the exhaust system and cat looks different from Dwayne's with two sides joining at rear silencer. As a result the inner joint is blocked from lowering by the exhaust. It might come out with the outer end free, but as it is there's no room to tap the other end inwards from the hub, so I will have to lower exhaust to give the inner joint room to drop.

The cat looks different from Dwayne's, and instead of a square joint at the cat there is a clamp. I do have the exhaust hanger off (took them off to change flexible brake hoses), so from experience with exhausts I'm worried that when I remove the clamp at the cat, the pipes will still be frozen together and the exhaust won't drop. If I was changing exhaust destroying the centre section to separate it from cat wouldn't matter, but I want to keep mine!

So how should I drop the exhaust for this type of clamp joint? Will it just separate when clamp is undone (done mind destroying a clamp).

Thanks a lot,

Adrian

Rodrv6

Your system may be similar to the one on my 88 S4. The first time I dropped the exhaust was when the car had 96,000 miles on it about 2 years ago. The clamps near the convertor came off after a good soak of PB Blaster. I sprayed it onto the slip joints and was able to twist the exhaust pipe and work it off. If that doesn't work, you can try some heat from a torch to help it free up.

mike77

When I put my xpipe on I cut the bolts on the clamp and then sprayed penetrating fluid. As mentioned twist and pull it until it comes. I think I remember lying on my bag pulling with my hands and pushing with my feet.

Good opportunity to wack in an xpipe and rmb

FredR

Adrian,

My exhaust system is quite [totally non standard] different to yours but I nonetheless dropped everything from the exhaust manifold connection backwards to create working room. Whether you need to drop everything is a moot point but reckon it is a good thing to do just to make sure everything is serviceable and can indeed come apart. The bolts on those clamps look somewhat encrusted but should come apart OK and if they do not then they need replacing.

Takes me about 5 minutes each side to drop my exhaust so no issue really. Yours might be a bit more tricky assuming those are cats fitted in your photo. You will have a need to disconnect the O2 sensor sooner or later so better to ensure you can do so when needed.

Rgds

Fred

StratfordShark

Thanks all.

I just got the clamp off - the nut was badly seized on threads so I dremelled right through the bolt in middle of clamp.

Have sprayed on more penetrant where the exhaust slides onto cat, but it doesn't feel as if it will ever move there. Stuck for now!

FredR

Why not unbolt at the three bolt flange on the exhaust manifold?

StratfordShark

That's interesting idea Fred. You mean on both sides so that cat can be dropped along with exhaust? How is the O2 sensor removed from cat to allow it to drop? Sounds easier than separating at the mud-section/cat joint.

AO

You can just unscrew the O2 sensor. Wires will twist up a bit, but it should make it easy peasy. You can also just cut the wires and replace the O2 sensor while your at it.

soontobered84

The O2 sensor is disconnected in the passenger footwell and the wire is removed through the hole on the passenger side of the tunnel. You will also need to remove the air tube connection that comes from the air pump. After these are disconnected, and the remaining mounting points are released, the whole exhaust system can be lowered at one time.

dr bob

IIRC, the right-hand side half-shaft came out with no exhaust system removal at all. Once the drive flange bolts were removed, the half-shaft was moved and supported at the end while the stub shaft was driven from the outer hub. No problems getting it out, in fact had to support the inner end.

For the left side, I did need to remove the muffler, just at the rear clamps though. Usually when one boot fails, the others are not far behind. Since the mess with cleaning and repacking the joints is the same for four as it is for just one, to me it made sense to do all of them at once and be done for another decade or two.

StratfordShark

This is intriguing Dr Bob. Maybe I've missed something, but the second photo in the original post tries to show the inner joint resting on the exhaust on right side. Problem is with the inner joint disconnected, there didn't seem to be any place to put it which allowed any movement towards centre of car when I tried to tap stub out of hub (didn't try to hard, but it didn't move at all).

If the inner joint can't drop below that exhaust pipe, how did you create space for movement toward centre when pushing stub inwards? On my car that exhaust section means no place to support the inner joint that allows movement to push the stub in and clear. Would be fantastic if I'm missing trick and it's possible!

G.P.

If you decide to disconnect the O2 sensor at the passenger footwell and remove the wiring when lowering the exhaust, be careful when re-installing to make sure the wiring goes through the floor correctly, because it is difficult to re-route the wiring when the exhaust has been re-installed.

mike77

I was initially beaten by mine. Left the penetrating fluid on it overnight and then had another crack and it came. Twisting it gets it moving and gets the penetrating fluid working.

StratfordShark

Thanks Mike I'm going out to have another go at twisting it off, has had fluid on it overnight.

Posting some new photos to make issue clear in case the cat exhaust is different on cars outside US - mine is a MY91 with cat installed and the double silencer tailpipe.

The photos show:

1. inner joint (now unbolted) in its position at the diff, so you can see where the exhaust runs relative to the joint
2. exhaust run looking towards front of car to get wider perspective
3. inner joint pulled down from diff and trapped by the exhaust pipe below, and fuel tank heat shield to rear (if I could get the heat shield off it may help, but not sure how it's attached

If I move the inner joint to get the most space between it and the diff, then there's only about an inch or less room. When i start to tap the outer joint through the hub this space is soon used up, and stops the outer stub moving any further.

So I can't get the shaft out unless that exhaust/cat joint separates.

Do US late S4s have different exhaust layout on RHS? Can anyone post photo of what a US 91 S4 "muffler" layout looks like? I'm puzzled why for everyone else removing the RHS shaft is easier!

Thanks

FredR

Adrian,

When I did mine I took one look at the installation and concluded the exhaust pipe has to come off at that location given you are also constrained by the fuel tank and what is the starboard [RHD driver's] side. On the other side there is quite a lot of clearance but I nonetheless removed it irrespective of what might be possible.

Not sure it makes any difference but do remember the half shaft concertina's along the joints but whether that can get you sufficient clearance to remove the shaft I do not know but would be surprised if it did.

Rgds

Fred