Flex Pipe Exhaust repair

[26DIPP]

My daughter's FII - BXW engine - failed its MOT because of a leak behind the flexible exhaust pipe.

 

I bought a kit on Ebay which included the flex pipe, 2 x 48mm clamps and exhaust putty.

The exhaust had a small leak at last year's MOT which got an advisory and we should have fixed it really for this MOT.

Well, I tried with a larger hose clamp and sealant but it did not convince the tester.

I started by marking the cuts on the exhaust pipe and undid the front end to the manifold. There are 3 x 16mm bolts to take off which can be a little stuck, and a XZN bolt.

I left the back section in place and cut with a small angle grinder that part straight and did the front end on a bench.

The replacement fits over the old exhaust. The OD is 45.2mm and it was a good and tight fit with the new part. There is about 5 cm overlap on the old exhaust.

 

I tried to clamp it first without the exhaust putty but still had a small leak so had to fit it with exhaust putty and the leak was gone.

 

Edited 21 November, 2021 by 26DIPP

[WezFab]

Looks like a neat job in the end, I've just got an advisory for this stating 'minor leak' will try take a look before next MOT I guess 😆

[Breezy_Pete]

Keep an eye on fuel economy. Even a small leak can affect the info the rear lambda sensor feeds back to the engine ECU with potential impact on fuelling.

The flexis, in my experience, tend to be more broken than they appear when both ends of the section are still attached and supported by the rubbers. Disconnecting the front end to allow more exploratory movement may reveal significant damage.

 

[WezFab]

Thanks will do, it's not an expensive fix either, will take a look sooner than later.

[J.R.]

I would not use the supplied U bolts & use stainless Mikalor clamps instead, they remain circular and spread the load over a much larger area so do not distort the pipe creating leaks, they are dirt cheap to buy.

 

I recently replaced the sleeve joint to the rear pipe on my Yeti, the clamps rust away, bought a new assembly and also 2 Mikalor clamps in case it didn't fit, in hindsight I did not need the new joint which will in time rust, the inner sleeves of the old joint are stainless, you can simply knock off the rusted remains of the old clamp and use mikalors in their place.

[WezFab]

Great advise thanks 👌 - I've not looked under the car yet - assuming it's not already had a bolt on replacement fitted.. anyone know if on a mk2 i'll need to cut out the original first? thats probably going to be the nasty bit.

[WezFab]

Little update, decided to spray a little water on my flex joint and take a look.. does appear to be blowing a bit to the rear (aren’t we all). Got some video and pics for your enjoyment 😆

 

Measured up for appropriate Mikalor clamps too. Time to get busy.

 

Video: 

 

[WezFab]

Also wondering if anyone would advise adding sealant when doing this bolt on job?

[nta16]

Mikalor clamps are welded and can go at theses points, they may be absolutely fine for your use but have a look a Norma clamps instead as they have folds.

 

[WezFab]

On 21/11/2021 at 21:31, 26DIPP said:

The OD is 45.2mm and it was a good and tight fit with the new part.

 

Can't stress this enough, Just finished the job on our mk2 there was lots of cleanup/sanding/filing required to get the fit needed without any gaps left by the cutouts on the new flanges.

 

I opted to leave everything in place and just cut the old one out - if anyone else does this, make sure you have access to a reciprocating saw as there is not enough room for much else to complete the front side cut.

 

If i did it again i'd preferably have something to make the cleanup simpler too, perhaps a wire brush attachment for drill/grinder.

 

Anyway.. managed to get a good seal with the Norma clamps and sealant for good measure, no leaks yet! 🙏

 

Cheers'n

[nta16]

Personally I'd just check the clamps (especially if s/s) after a couple of heat cycles.

 

Doesn't apply here as the OD would be within the range of the clamps but personally I have found if the OD is at an extreme of the clip's range they're not a reliable as an exhaust clamp.