Xantia V6 broken exhaust (update: and rough low rpm running)

[Mandrake]

Well the other shoe has dropped it seems.

Out for a quick drive tonight looking at houses and noticed that the exhaust got very rapidly louder, pulled over with the suspension right up to look underneath and my worst fears were confirmed. The coupling between the cat and the centre silencer has completely broken away.

Limped very very noisily home a couple of miles with barely enough power to get up the hills, put it up on stands and found this:

The outer sleeve of the cat has broken away completely (still clamped to the silencer) and the rear section of the exhaust has slid back so far that its only hanging on by a thread - slightly more and the centre silencer would have fallen down and plowed head first into the road most likely destroying the rear half the exhaust system.

I knew the joint was on its way out, see this thread:

http://www.frenchcarforum.co.uk/forum/v ... =3&t=40798" onclick="window.open(this.href);return false;

In hindsight I think this joint working its way apart is the cause of both the car not running smoothly at low revs, and the shuddering/vibration at low revs, as discussed in this thread:

http://www.frenchcarforum.co.uk/forum/v ... =3&t=41141" onclick="window.open(this.href);return false;

My biggest concern is whether the cat falling down at such a steep angle may have damaged the joints between the engine and the cat ? Here is how much it was sagging when I got home:

It looks like there is some sort of spring clamp arrangement between the cat and the engine manifold that gives a degree of freedom of movement, is that likely to be still ok and still sealing ?

Continued in Part 2

[Mandrake]

It seems that the inner sleeve of the cat is still fine, but the outer sleeve has broken clean away, here are a couple of views, one from each side:

Grasping the silencer and pulling the two together again I was able to reposition it like this:

However there is nothing to hold it like that at the moment. At the very least I'm going to have to bodge some sort of clamp to keep the two sections from sliding apart to be able to drive it to be repaired.

I'm unsure what to do to get it fixed, because as per the thread I linked to regarding the cat two places I already took it to last month when it was just a minor leak simply wanted to replace the cat and silencer for hundreds of pounds and I literally have no money left that I can spend on the car this month...it does look like the end of the middle silencer pipe is burnt away but the cat may still be salvageable...

I'm now without a car right when we were looking at houses to move to...but that's the way things go aren't they!

I'm going to have to do some sort of quick bodge so I can at least move the car, even if it is a bit noisy. Perhaps a second clamp to keep the two sections sliding apart and a bit of exhaust paste will get me by until I'm paid at the end of the month ?

Any advice folks ?

[CitroJim]

That's the normal way they fail Simon. Now, Mine on Old V6 did and enough of the outer cat sleeve was left to get a couple of big Jubilee clips around it and clamp it back up again. That 'modification' lasted for two years...

Now, that old cat is valuable as if it is replaced it'll be with a little kitten and you may have trouble at MOT time. I reckon a good exhaust place could repair the tail of your cat and weld a new sleeve on with very little trouble. That's what I'd desperately try to do in order to save the cat. Such a repair may involve the sacrifice of a silencer box to obtain a ring but that will be cheaper than a new and possibly inferior cat.

I doubt any damage will have arisen with the cat falling as it did. The cat to header collector joint is a normal PSA 'brillo pad and springs' job and has plenty of give in it for such an occurrence.

Hope it all comes good and the cat can live on...

[Mandrake]

I'll do what I can to save the cat... I don't mind getting the middle silencer box replaced (after I'm paid) if necessary.

To bodge it in the mean time I don't think any single clamp will work as a compression clamp won't be able to squeeze the outer tube to grip the inner one, and the flange is now separated completely from the cat.

What I was thinking was to add a second identical clamp to clamp upstream of the lip on the cat pipe (not too tight so as not to damage it) so that it is parallel with the other clamp, then loop a hose clamp on each side through the bolts of each clamp so that when the hose clamps are tightened they pull the two clamps closer together - thus pulling the two pipes together.

Do you think that would work for a few weeks ? Can't be any worse of a leak than there was there before, and should be stronger than the tiny bit of rust that was keeping it together before!

[CitroJim]

That should work Simon as there's a good two inches of sliding surface between the cat and mid-section. A good tight clamp and some metal packing and exhaust paste wrapped around the tail of the cat might well work a treat and may last longer than a couple of weeks...

[Mandrake]

Not sure if you followed my idea Jim

I'm not talking about clamping on the 2" overlap region between the pipes, I think theres too much diameter difference between them (unless I packed a spacer in between) for that to work - they're not a snug fit, presumably as they're not expected to seal there when the outer sleeve is intact.

I meant to clamp to the left of the lip on the cat pipe in the first photo then use the hose clips to pull the two clamps together horizontally. Might be an idea to smear some sealant on the overlap region before pulling it together as well.

[CitroJim]

Ahh yes, I see what you mean Simon. That'll work fine and will be secure but for it to be gas-tight (ish) I guess you'll still need to wrap some metal packing over the tail to make up for the diameter difference. Old tin cans are almost perfect for making packing.

[Timmo]

what i'd be tempted to do would be trim away the rotten metal, up to where the clamp is, as seems it stops around there, cut 2 slots about an inch deep into the end of the pipe to allow it to collapse a little when clamped, pop a fair bit of 'gumgum' in there and pull them together, ive used a ratchet strap to great effect for this job befor on the wife's fiat, a loop around the pipe in front of the cat and a loop around the pipe at the end of the silencer and ratchet it up, tighten the clamp up as much as you can,
the idea with 2 clapms and pipe clips would work and i like it!! would be great at holding it together,

another option, measure the diameter of the pipes, you may be able to get hold of a reducer pipe for the system, 68mm-64mm for instance, i found some on the net donkeys years back when looking after the resonater went on the bx, managed to bodge it with some flexi pipe in the end,

[Mandrake]

No need to trim away the rotten metal, the only reason its still there is because the clamp is still clamping whats left of the cat outer sleeve to the silencer pipe. If I undid the clamp that bit would fall away.

I've already ordered another exhaust clamp, (hopefully the right size, I got 72mm) a couple of pairs of hose clamps with removable ends that I should be able to thread through the bolts and a small tub of exhaust sealant which will all hopefully arrive by Thursday/Friday which I have off this week, so that should allow me to bodge it to the point where its mechanically secure and the car is mobile, albeit possibly with a small leak. (It did already have a leak that passed the MOT with a warning before it broke anyway)

That will give me breathing room and mobility until I have a bit more money and time to figure out a more permanent solution.

A flexible pipe wouldn't work as it relies on that joint being stiff to support the cat and the silencer - any ability to bend there would let the cat sag as it has been doing when the joint has started to slide apart.

I do like the idea of the reducer pipe though - I saw a few different ones with slotted ends of about the right size while searching for the clamp. If I could find the exact size to be a close fit (or get one made by having two different diameter tubes welded together) I could could hacksaw the flange off the silencer, the cat already has a smooth neat end on the pipe suitable for a slotted joint, then I could just use a reducer pipe with two clamps and two slotted joints with a bit of sealant - not the same as original but it should be mechanically very strong and not leak, plus I wouldn't be making any changes to the pipe on the precious cat...

Before I can do that I'll have to get myself a vernier calliper - I don't have anything for measuring inside and outside diameters accurately! Next month...

[Mandrake]

A question Jim might know the answer to - when the pipe separated not only was the exhaust extremely noisy but the car lost most of its power - putting your foot down just made a lot more noise but didn't really give any more power, to the point where it was actually a bit of a struggle to get up some hills at 30mph - I had to put it into sport mode to keep the revs up as it simply wouldn't pull up the hill at normal revs. (Although it was very reluctant to rev as well)

Is this to be expected ? Does having the exhaust all leaking out before the silencer upset the flow so much that the lambda sensor would screw up the fuelling to the engine ? Was it perhaps putting the engine ECU into limp home mode ? Or is it possible the cat falling down has damaged the lambda sensor or its electrical connection ?

The last time I had an exhaust separate like this was on a GS where as well as making a huge noise it actually increased the power Of course it didn't have a complicated closed loop electronic emissions control injection system, just a carburettor and kettering ignition

I'm just hoping it hasn't done some other damage. I have certainly noticed a bit of a lack of low down pull and smoothness below 2000rpm in the last few weeks, (as discussed in the funny engine noise thread) and I suspect that hole has blown out significantly in that time period. So are the two connected ?

[Timmo]

When the BX pipe slipped off from the resonater it did much the same! Lots of noise very little grunt, engines Do need a crtain amount of pressure in the system to work efficiently (petrols for sure,), was a really good little guide in a mag several years back about how the system works,

[Mandrake]

Ah thats a relief to know, and that could explain the loss of performance and rougher running recently, as the exhaust leak had got noisier...

I've just looked at my photos again and have realised that a size reducer pipe could only be fitted if I cut a significant amount off the silencer pipe (I'm not willing to cut the cat pipe) so it may not be as practical as I thought. Will have to give the best approach a bit of careful thought.

[Timmo]

i was thinking more that a reducer could be used to sleve over the cat pipe And onto the rusty section, not actually cutting away at the cat pipe, but fitting it as a sleve joint over the two, depending ofcourse if you can get one with a small enough reduction, would imagine it would only be a couple of mm difference ion size between the 2 pipes,

on the verniers, a few years back i picked up a plastic set form my local surplus tools shop, there not uber acurate but for the sake of 50pence they did a pretty good job! there out and about under the usual pound shop tool brands, also picked up some from lidl when thay last had them, with a digi display for £7 i think they were, obviously there not going to be as accurate as the proper engineering ones but for the likes of the casual diy'er there spot on!!

[CitroJim]

I'd very much concur that the exhaust falling off will have a detrimental effect on power. I've an ongoing thought that my V6 is a bit down compared with the two other V6s I've had close association with and I'm now leaning toward the exhaust.

The car has not been used much these past couple of years although it is now. The back box, whilst intact, is very rusty inside and the centre section may be full of rust too judging by the amount that fell out of a good second-hand one I've had lying in the garden for a couple of years.

Being used more now, mine is improving and maybe as a result of a good run on Friday blowing a lot of rust and rubbish out but i feel I may not see the full pep from the car until the centre and back boxes are replaced...

[RichardW]

Simon

I reckon there's two ways to go with this...

1 (no cost!) - remove the silencer and cut the end off its inlet pipe. Cut 2 or 3 slots in it, slide it back on and crank up an exhuast clamp on it. This is effectively the method used on the HDi repair pipe and should make a permanent solution. You will need to modify any future replacement silencer to suit though....!

2a (costs a bit....!) - Not sure which part of the joint is on the cat and which on the silencer. If it is the bellmouth on the cat then you could buy the HDi repair pipe, cut the end off, slot it if necessary slip it on the cat and weld it into place. This would give you the 'original' arrangement, and any future centre silencer would still fit.

2b (Costs more) - if the other way around (eg bellmouth on the silencer) then you will need to buy a silencer (eg a rear box - mind you I got one for a Picasso HDi for £30 so maybe not that dear!) cut the lip off, and weld onto the cat as before.

My thought is that 1 will work no problem at all and saves having to remove the cat from the car.

I am at home this weekend (sans family!) but will be head down - arse up tiling the porch floor. However, you're welcome to come and use my facilities (ramps, grinders etc) and I can provide welding as required. I'm back on Thursday, drop me a PM and we'll arrange something.

Edit - of course if you are desperate, there is always Citroen:

Part Number Description Quantity Price excl. VAT Price incl. VAT Total incl. VAT
0000173177 CATALYST MUFFLR 1,192.52 GBP 1,431.02 GBP