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Go Back   TDIClub Forums > TDI Model Specific Discussions Areas > VW MKIV-A4 TDIs (VE and PD)

VW MKIV-A4 TDIs (VE and PD) This is a general discussion about A4/MkIV Jetta (99.5-~2005), Golf(99.5-2006), and New Beetle(98-2006). Both VE and PD engines are covered here.

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Old September 20th, 2009, 13:25   #1
mk3
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Default Front pipe with CAT - replace or repair (many pics)

I have driven my car up onto some solid concrete blocks so I could do an inspection before winter and I found some imminent problems with the exhaust.

1. The area just behind the weld on the rear of the cat is thinning and has a hole
2. The area at the front of the splice clamp has corroded and lost about .7mm material.
3. The hanger behind the splice clamp rusted off (no pictures, I can repair this with U-bolts but the part cannot come out from the car withouit cutting it)

These relatively small-looking problems are theorically big $$ to fix with new parts. More than $600 for the front pipe with CAT.

Here are some pictures and notes

This is the whole pipe (below) with the pertinent areas noted.

This is just behind the cat - notice the thin material and the hole



The front bracket is pretty rusty - I wonder how much longer it can last



This area by the flex joint looks good!



There are some orange-colored bubbles in the bottom of the pipe -curious. They look a little like stalagmites and are sticking out out of the soot which is very thin.




The clamp was pretty easy to remove. note there is about 25mm to 30mm gap between the two pipes. You can see the soot showing where the gap was. I did not have to use anything other than a breaker bar and socket along with a prybar to spread the clamps apart. I counter-held on the front pipe to keep from stressing the flex pipe.



This is the end of the front pipe - the area adjacent to or just under the end of the clamp was very rusty. This is what is left after I knocked the rust off. I am concerned that if I repair the area by the CAT, this migh just end up breaking next. It's interesting that most of this pipe has no rust at all (still shiny silver). Just behind the splic clamp the pipe has a patina of rust. I'd bet all of our cars look the same way - the alloy is clearly different.



The OEM flex pipe is nominally about 8 inches long and looks to be in very good shape.




The OEM flex pipe is nominally 2.5 inches OD




I bought this reducer adapter at Farm & Fleet. It is potentially a repair. I can have this welded on for low cost I would guess. The down side - the peice is not stainless and the new welds might quickly rust anyway..




I'm not too thrilled with the idea of any non OEM parts. I had a few bad experiences over the summer trying to fit air conditioning parts that were not 100% fits to OEM. I know that tdiparts.com has a nice looking system but it is not the stock shape and I am just super-paranoid about making any changes. I'd love to have some suggestions about other repair methods that would be long-lasting such as stainless peices or good weld techniques.

I'm happy to have the chance to repair this at my leisure instead of one day just having the pipe snap off as I've heard happen to others. This is the first time I've had any of my cars up high enough to comfortably crawl under them and I think I'll make it a bi-annual habit to do so for repair of undercoating, exhaust, etc.
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Old September 20th, 2009, 14:53   #2
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You need to figure out how much you want to spend or can spend on fixing the car. I like your idea of welding the pipe adapter over the failing weld. Take the exhaust system to a muffler shop and see if they can do this and use the clamp to fix your hanger that rusted off. It's that or going new for the whole works in my opinion.

--Nate
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Old September 20th, 2009, 18:47   #3
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I know how much money I want to spend - I always strive for the best value so I if I have a good argument for the $600+ on the new OEM part being a good value then I would do it.
I should have said that I intend to keep the car for the long haul - probably until about 300k miles or about 7 more years at which point it will be 13 years old.
A good question to add:
Do CATs wear out with regards to their function? The CAT does not look like it is breaking down on the inside - I looked in there and it looks like a very clean grid structure. Here in Waukesha County, WI we do have emissions testing for now and I would want to keep the emissions system in good shape anyway.
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Old September 20th, 2009, 19:10   #4
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If it was my car I would get the part from TDIParts. Second choice would be this from German Auto parts. I would bet the rust is going to cause more problems. When I try to weld rusted metal I tend to blow more holes. Sometimes I get something to work but I am a shadetree welder. Of course a lot of muffler shops have marginally skilled welders. http://www.germanautoparts.com/Volks.../Exhaust/51/20

My TDI converter does not clean up the stink like it did when new. It is on my list of parts to replace. No salt where I live so I may go cheap and just weld in a new converter. My gas truck has a 20 year old converter. Insides look ok. No emission testing in my county so I can only assume it is doing its job. I know the exhaust smells better than cars I have been around with no converter.
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Old September 21st, 2009, 11:25   #5
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I order from germanautoparts.com a lot but looking at that front pipe I think it is not stainless, but rather is aluminized. I am _assuming_ that because it doesn't say it is stainless but I wouldn't know for sure unless I called them.

I wouldn't try welding onto a rusted section. I was thinking of getting a piece that would go upstream of the damage to downstream of the damage totally spanning across the damaged area - that's the theory anyway but I haven't found a good piece yet.

Today I am trying to figure out how to clean a CAT or determine if it is bad. I found some info saying you can clean them by compressed air blowing backward out of the inlet. I'm sure this wouldn't be 100% but it may get rid of some soot and increase the efficiency a bit. The same document said that standard ones can be reversed to get more life from them. However, the OEM one is not symmetric and that would be too much disruption anyway.
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Old September 23rd, 2009, 09:50   #6
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Quote:
Originally Posted by roadhard1960
............My TDI converter does not clean up the stink like it did when new.........
That's what it's supposed to do? why would you want to do that? The smell is the best part about owning a diesel.......



with apologies to Francis Ford Coppola, and "Apocalypse Now"

I love the smell of diesel in the morning........
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Old September 29th, 2009, 12:31   #7
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well, the smell of off-road diesel causes nice memories for me since it reminds me of the farm and my younger years... however my TDI never smelled like the tractors.
I just took my front pipe to an exhaust shop and they tell me the front pipe parts are not stainless and the tube from the CAT-back is aluminized.
Does anyone know for a fact what the factory/OEM parts are made from?. I assumed 409 stainless but this guy checked with a magnet and said it's not. I was under the impression that all factory exhausts of modern times are some alloy of stainless...?
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Old September 29th, 2009, 13:48   #8
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I'm not sure where you got 409 from, but the "magnet test" would show that 409 IS magnetic. Your guy is mistaken. There are a bunch of alloys of stainless that are magnetic.

Interesting science lesson here: "Stainless" is defined by >10.5% chromium. But it's the nickel that screws up the magnetic properties of the material. Anything over approx 4% nickel is non-magnetic. 300 series stainless steels have both chromium and nickel, therefore they are non-magnetic. most 400 series has chromium, but no nickel (or very little), therefore they are magnetic

Back to the original question, i'm not sure what the vw exhausts are made from, but mine rusted out in the pipe aft of the cat, and forward of the double-bolt coupler. Everything else looks fine. I replaced that section only with 304ss, and no issues since.
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Old September 29th, 2009, 14:08   #9
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A coworker told me it is likely 409 at least on some of the parts. Subsequent research on the internet shows that 409 is a common material for auto exhaust systems.

Where did you get the 304 stainless from? Did you find 55mm material? I would like to do the same thing but as stated below the shop I went to didn't even seem to know that stainless can be magnetic???!! and I have searched high and low on the net and not found a suitable source.

I'd like to be able to use the OEM clamp between the front and rear sections - I have purchased a new one.
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Old September 29th, 2009, 14:37   #10
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I had the tubing laying around. it wasn't exactly the right size. I was able to sleeve it with 304 machined fitting to get it close to the right size.

Good luck finding 55mm. I couldn't find it.

You can find plenty of people who supply tubing in inch sizes. Two of my favoites are Burns Stainless, and Columbia River mandrel bending. Good 304 tubing isn't cheap.

http://www.burnsstainless.com/304tubing/304tubing.html
http://www.mandrel-bends.com/catalog/tube-pipe-bar-38/
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Old October 16th, 2009, 16:37   #11
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Thanks Mike944!
Those are indeed very good sources. I ended up buying two pieces from mandrel-bends.com This was my order:

2 x 2.13" OD, 16 Gauge, 304 Stainless Straight Tube
1 x 2.25" to 2.75" Transition Cone
1 x Expansion Service

I got lucky and the straight pipe fits inside the transition cone. This will not always happen but they can still be butt-welded. I ordered 2 feet of tube but you can see from the picture that I only needed 1 foot.

I asked them to expand one end of the tube to 55mm OD so I can use the OEM clamp. You can see the expanded area adjacent to the clamp in the picture.

next stop - the local weld shop! I'll have them fixture around the old pipe and then cut it off so the new pipe can be exactly where the old one was - at least that's the plan.
This should come in under $100 total for the repair.
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Old October 21st, 2009, 21:03   #12
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What is the size of this piece of pipe,(the one used for the fix, not the actual exhaust part) ....I need to weld this onto my car, I have a small hole starting, .and would like to do it before winter hits!!!

2" - 2 1/2"???

thanks

EDIT: HA HA never mind, it is written on the label on the pipe, .....ID 2 1/4 reduced to 2 1/2
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Old October 22nd, 2009, 05:12   #13
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pbraunton, I didn't end up using that piece although you could because it does fit fairly well (The 2.25" ID is a little big for the 55mm pipe). The reason I didn't is that the other end of the pipe off the CAT was corroded a lot underneath the clamp. It would not have held for much longer.

refer to the post just prior to yours for the actual parts that I got from mandrel-bends.com in the event this happens to you. The biggest advantage of getting the pipe from them is that they expanded one end to the stock O.D. of 55mm for $2.50 US additional.
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Old October 23rd, 2009, 19:24   #14
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Finished!
Dan at repairspecialties.net in Johnson Creek did the welding of the 304 stainless part for me. He created a simple fixture to make sure the pipe's alignment was the same as the old one. Looks good to me! now it should be a simple bolt-up job.

He said he had to do a bit of filling at the end of the transition piece but that is the best part I could find .. and I looked at a LOT of places!
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Old June 1st, 2010, 14:14   #15
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not bad, looks like it will do the job, how has it been holding up?

my solution has been working for over a year now
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