TDI flex downpipe repair/replace

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VAG Fan
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Location: Pretoria

TDI flex downpipe repair/replace

Post by VAG Fan »

My Mk4 TDI is starting to make a "fuzzy" exhaust sound from the front, and is also starting to smell of exhaust gas inside the car. I have a hunch it's the flex downpipe that's starting to go. (The one with the braided sleeve). Obviously I still need to confirm.

But supposing it is indeed the flex downpipe, any advice?
Can the flex section be bought separately and welded in?
Anyone around Pta. East (exhaust shop or otherwise) who you'd recommend to do such a repair properly, first time around?
Mark R.
- - - - - - - - - -
2004 VW Golf TDI, type 1J, AHF, 317k (2016-current) --- daily
1990 VW Fox, type 16, HM, 304k (2005-current) --- spare runaround
Previous:
1992 Audi 500 SE, type C4, AAR (2001-2020) --- nice while it lasted
1983 VW Golf GTS, type 17, FR (1992-2005) --- most fun car I've ever had
1978 Audi 100 GLS 5E, type 43, WC (1991-92) --- died in the side of a Rekord who cut me off
- - - - - - - - - -
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missioner
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Car Make: VW
Car Model: '87 MK1 Golf Citi

Re: TDI flex downpipe repair/replace

Post by missioner »

Yes it can be bought and installed without replacing the rest of the pipe.

Unfortunately I think the problem lies with the manifold gaskets, they are usually the reason for a "fizzing" sound. The reason for the noise is the gas passing the gaskets as the no longer close the gap between the manifold and the head.

The best way to test is to block the exhaust and go have a listen at the front. If it's difficult to pinpoint the leak, use a pipe like a stethoscope. Hold one end to your ear and then use the other to see where it's leaking by holding it near the gaskets and joins.
'87 Golf 1 Olde Skewl OEM+
VAG Fan
Lieutenant
Posts: 1440
Registered for: 8 years
Location: Pretoria

Re: TDI flex downpipe repair/replace

Post by VAG Fan »

Thanks for the response.

Good news that the flex section can be replaced if needs be.

Indeed I was wondering about gaskets. I must say, though, that there is no rhythm to the fuzzy or fizzing sound. It's very light, and very even, and only audible at idle. Under load and higher revs, there is no audible abnormal noise. The manifold leaks that I've heard up to now, were all rather well defined and pulsing, and grew louder with load. This is why I'm hoping it's further back.

Also, the Garrett OEM-spec turbo (I think, a GT1749VA) is manufactured as one casting that includes the manifold. This was replaced just over 2 years (about 30k km) ago - I did this together with Panic at his place. So I would hope that the gasket isn't failing already.

Either way, good idea to pinpoint the fizz with a pipe stethoscope. I'll try that.
Mark R.
- - - - - - - - - -
2004 VW Golf TDI, type 1J, AHF, 317k (2016-current) --- daily
1990 VW Fox, type 16, HM, 304k (2005-current) --- spare runaround
Previous:
1992 Audi 500 SE, type C4, AAR (2001-2020) --- nice while it lasted
1983 VW Golf GTS, type 17, FR (1992-2005) --- most fun car I've ever had
1978 Audi 100 GLS 5E, type 43, WC (1991-92) --- died in the side of a Rekord who cut me off
- - - - - - - - - -
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