On the Polo, with BBY engine, there's been a farty noise especially from cold that I've been wanting to get rid of for a while now.

This years MOT was fine, slightly higher HCs than I'd like but less than half the limit IIRC, nothing noteworthy about the CO or lambda numbers, both easy passes.

The MOT before, under previous ownership, a 'slight exhaust leak from front' was an advisory. Guess this is what I've just found.  I disconnected the front pipe from the maniverter and released the front rubber support, hoping I could drop it down a bit and examine all around the flexi for cracks or whatever.  As soon as it was free at the front end though, I found I could unexpectedly rotate the thing. Turns out it's the rear end of the flexi that's come away (red arrow shows the separated bits):

 

 

 

 

 

A shot from further away for the bigger picture:

 

As this pipe contains the main cat and the rear oxygen sensor which is probably well 'bedded in' there by now, I'm reluctant to write off the whole front section, genuine's gonna be big bucks, pattern might be nasty/loud/poorly-catted.

 

Worth trying a bolt in repair flexi? Like this? I'm a bit doubtful because of the closeness of the hanger bracket, and the funky angle that's incorporated into the OEM pipe, shown by the two horizontal-ish red lines in the first photo, and easily visible in the second.

 

Better to take the whole thing off and get a replacement flexi section welded in, presumably?

 

 

Thoughts?

Ta.

Ive changed two of these now.

 

One on a BBY and one AUB. as im sure you know come as a downpipe + flexi + cat system.

 

£80 for a patent part from ECP but the Cat obviously wont be of an OE quality.

 

 

If i could weld i would remove the pipe from the car, measure the Flexi size (Outer D, Inner D and lengh) then buy a new flexi at just weld that in. (as you have said)

 

 

Or just put a bake bean can over it to seal it up. im sure its not an MoT failure if it were to be done.

Blimey, that ECP 'React' part is temptingly cheap...thanks for that suggestion.

 

I can't weld, but I know a man who can, it's just he's so skilled at so many things, he's always busy!

Wife's BBY Polo had this issue by its 5th birthday which I found a bit annoying!  I found a local exhaust specialist who welded in a new flexi, but it was the wrong diameter and length so caused a lot of noise and clunking! Not happy at all as this guy designs and fabricates stainless steel exhausts for a living, so, I found "senior alfermarket" and after doing some measuring and getting someone on this forum to do the same, worked out exactly whicg size of flexi repair section I needed, bought it, got same exhaust specialist to weld it on "it will be just trhe same as the one I fitted!", car was perfect until I handed it in against a new Polo last Wednesday.  If you search using the correct terms, ie flexi - no it must have been lost, I'll have a look at my old Polo records and tell you which size to get.

 

Is that stainless steel (marine) cable ties I see in your picture, if so, that is what I bought from Screwfix when I first tried to quieten it down, I could only get the short ones so needed to splice two together! (failed to seal though)

To be honest, the repair section that I bought should cost about £45 now (guess), I was charged two hours labour which back then all came to about £100 which was peanuts when compared with the only alternative - ie VAG!

Update:- use "senioraftermarket" as the search term and it will find the correct threads. 

 

"Exhaust flexi alternatives"  the final posting by me says which repair section I bought that worked.

 

I've just looked on that site (senior aftermarket) and they don't seem to list repair sections, ie flexis with tails - maybe email them quoting the part number I bought from them, they were very helpful and keen to supply a DIYer.

Edited 16 August, 201510 yr by rum4mo

Thanks rum4mo, I appreciate the info. 5 years to failure is terrible! I would have shared your annoyance.

 

Yes, stainless tyrap that we happened to have some of at work. At the time, just after purchase, I thought I was just retaining that end of the covering mesh with it, as that had broken away. I didn't realise then that the damage was deeper too. It was only when I replaced the badly holed rear silencer that I started to notice the noise from the front.

 

Fortunately the broken join where flexi ends seems to be sort-of sleeved over an inner, smaller diameter bit, so it doesn't seem like its going to completely drop off any time soon. Gives me a bit of time to ponder the best solution.  Welding seems likely to be the way to go.

I would be tempted to put a smaller flexi in, and get a bend welded onto the rear end so the flexi is sitting straight.

^ Good thinking. Ta.

I would be tempted to put a smaller flexi in, and get a bend welded onto the rear end so the flexi is sitting straight.

 

For me, the shorter flexi just caused other issues, though it was also larger diameter!  The close proximity of the upstream bends is a real problem, I has concerned that my first repair attempt by my exhaust fixer might have removed a part of the bends and so trashed any future repair, but it didn't. The next issue is the proximity of the support bracket and the proximity of the cross member to that, they can all make life awkward .  I have a feeling that once you know the ideal dimensions of a repair flexi, places like ebay can identify who sells them. (I discovered this later when helping someone else)

 

It was the same sort of issue with wife's car at 5 years old, ie looked like lack of welding at initial assembly of that section of exhaust, absolutely no damage to the anacondic flexi or the second weld.

Edited 16 August, 201510 yr by rum4mo

I reckon something like this fits the bill. Will check measurements in the morning.

At that price I'd be buying the Euro one. Job's done and dusted then (as long as the Lambda sensor comes out of the old one OK).

^ It's a strong temptation Lee, they even have one in stock at my local branch less than 5 miles away.

Anyone know any ecp discount codes that currently work?

 

I can keep the old one and mend it at my leisure if the React one turns out to be too loud, or doesn't last well cat-wise.

Could even 'cut and shut' bits of both...   :think:   

All done with the ecp one. Tweet5 gives a 5% discount.

Pipe joining clamp was a mission, and had to take off a few plastic covers and cross-brace to get at lambda connection and to be able to get a hacksaw on the clamp.

Lambda sensor also fought back, but putting it in a vice and turning the pipe worked.

You mentioned replacing the rear box, well I got away with fitting a stainless steel Jubilee clip round it to keep the outer covering on, last MOT said something about rear box though. Anyway, I finally parted company with that car after 12 years and 11 months and 106300 miles all from new. It still had original starter, alternator. clutch, exhaust (except flexi), battery, steering pump and two original coils, which was good enough for me. There was a temptation to do it up and sell it on privately, but it would need a new back box - and that might have caused other issues (like a repeat of the flexi), probably a new O/S rear calliper and new rear pads and discs - even then it still had rusty bits so would probably just cover my parts bill - so it got chopped in against a nice new Polo 1.2TSI SEL, that should keep wife going for a few years! Bonus is these 1.2TSI 110 engines make some strange noises just to keep you alert!

 

So far, in my driving life, I have "used" two VWs, B5 Passat 2.8 4Motion for 13 years 90000 miles, it needed a new battery and an exhaust front jointing piece due to a rusted through clamp, so I was keen to save money on battery and exhaust on this 9N Polo 1.4 SE.

 

My old Fords, bought new, liked new batteries and new exhausts as soon as possible please!

Edited 17 August, 201510 yr by rum4mo

Hehe, it would've taken a big old jubilee clip to fix my rear silencer. I took it into a local exhaust place to find out exactly where the 'motorbike' noise had suddenly developed from.

With it up on ramps he wandered round it with engine running, prodding and poking. He started at the front, and he didn't pick up on the flexi problem, which makes me feel better. When he got to the back box he suddenly laughed out loud and said "have a look at this". As I got to where he was pointing, he gently pushed his whole fist through a 'gauze' of rust.

 

There's hardly any rust on anything else, and the engine seems super-sweet at 120k miles; I'm chuffed to bits with it.

All done with the ecp one. Tweet5 gives a 5% discount.

Pipe joining clamp was a mission, and had to take off a few plastic covers and cross-brace to get at lambda connection and to be able to get a hacksaw on the clamp.

Lambda sensor also fought back, but putting it in a vice and turning the pipe worked.

 

 

Good stuff

Glad to know it was of some help. I did the exact same fix for Bossfox on one of his early FGF cars. same fault, front flexi was torn/blowing. £80 at ECP and the new part was fited, only problem i had was getting the old centre pipe join off (much like you did too by the sound of it)

Even more help than I thought yesterday, as it turns out.

 

With my ever growing enthusiasm for VCDS, I decided to log some lambda-related stuff before changing the cat, and I'm very glad I did.  I logged MBs 32, 33 and 37 before the change, and just now after it.  Both numbers in block 32 have shifted, and from MB37, the lambda voltage (original sensor) versus load for sensor 2 (downstream of cats) makes interesting comparative viewing:

 

Before:

 

After:

 

 

Can't see the small air-leak of the damaged flexi making that much difference, so it looks like the old cat was pretty sick anyway! :sun:

Update after new information appeared.

 

Last weekend I finally got round to changing my recirculation-flap motor to get rid of the only fault codes that VCDS had previously shown. That went well, but when I re-scanned afterwards I'd got an engine fault code I'd never seen before:

17584 -  Bank1: O2 (Lambda) Correction Behind Catalyst: Control Limit Reached
            P1176 - 35-00 -   -

 

Ross-tech site suggests that this is likely to be either an intake air leak (false air) or a lambda sensor problem.

As luck would have it, that evening I found a NOS genuine post-cat sensor on ebay for a bargain price, so snaffled it up quicksmart.

 

I've done a few logs and scans in the week, wondering if this could actually be the new aftermarket cat being rubbish, or the pre-cat being Donald-ducked, but couldn't really get anything straight in my head from the results.

 

Today I took her Fabia out for a comparison log, and immediately noticed that the post-cat sensor was behaving more like my Polo one before it got transplanted into the new flexi/cat pipe. Shame I didn't think of doing this at the time of the Polo repair.

 

Having now fitted the replacement post-cat lambda, I can see that the previous plot which I thought was showing a much healthier cat was actually telling me that the transplant of lambda sensor to the new cat pipe had killed the sensor.  I'm a little surprised that this didn't bring any fault lights on, and only intermittently seemed to log a fault code.  Out of about 4 or 5 logged/scanned journeys this week, only a couple brought that 17584 code up after being cleared at the start of the trip.

 

Anyway, this is a scatter plot of post-cat lambda voltage (y-axis) against engine load on a mixed journey, much more like the 'before' plot in the previous post. No fault codes logged during this trip.

 

 

Hopefully that 17584 code is history now.