Front pipe with CAT - replace or repair (many pics)

mk3

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03 Jetta GLS 5-speed
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.
 

PDJetta

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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
 

mk3

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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.
 

roadhard1960

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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/Volkswagen/Jetta/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.
 

mk3

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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.
 

mike944

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roadhard1960 said:
............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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mk3

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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...?
 

mike944

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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.
 

mk3

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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.
 

mike944

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mk3

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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.
 

pbraunton

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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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mk3

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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.
 

mk3

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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!
 

simbolo

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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 :D
 

turbocharged798

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^^^LOL, is that duct tape????


The same thing happened on the 99.5 so I took some aluminum flashing and two hose clamps and fixed it....until the flex pipe broke. The whole thing was rotting away, including the cat. Ended up getting a new 304 downpipe from idparts which is really nice. Cost some $$$$ though.
 

simbolo

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ha, no its muffler patch tape combined with sheet metal and hose clamps, it sags a little but keeps together, for now. Been eyeing that TDIparts or IDParts rig for a while now but have a TB job due so it will have to wait :(
 

mk3

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My repair with the part from Columbia River Mandrel Bending (mandrel-bends.com) has been holding fine.... naturally since it has only been a few months! I'll let you know in about 3-5 years which is when the bracket at the front will probably give out. I don't think I will have any trouble from the 304 stainless.

I didn't cover it here but I also had to repair the bracket that holds the pipe in the center of the car. It makes me wonder if there is some good product that could be applied pre-emptively to the welds and little sheet metal brackets of the exhaust components to delay corrosion....
 

coalminer16

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Reading through the post. Only safety bit I would add is I would NEVER go on cement blocks and crawl under the car. Those blocks can crumble since they aren't held together with any steel inside like roads and bridges have embedded in them. I would get proper ramps bought or made. Just don't want anyone hurt out of the deal is all.
 

mk3

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True about the hazards of working under a car on cement blocks. I should have mentioned that I use SOLID blocks and I have a very new, flat and solid garage floor. I also use jack stands as a backup.
 

simbolo

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well it finally happened, needless to say I had to replace it, installed IDParts 2" pipe..



 

IXLR8

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well it finally happened, needless to say I had to replace it, installed IDParts 2" pipe..
How well did the IDParts pipe fit up??
Some folks have expressed concerns since it was not bent the same as OEM that it would not fit well. My 01 Jetta with 238K miles is starting to develop an exhaust leak... I really don't want to spend that kind of money on this car... but safety inspections might force me to.
TIA
 

simbolo

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How well did the IDParts pipe fit up??
Some folks have expressed concerns since it was not bent the same as OEM that it would not fit well. My 01 Jetta with 238K miles is starting to develop an exhaust leak... I really don't want to spend that kind of money on this car... but safety inspections might force me to.
TIA
it fits up pretty well, except it sits somewhat higher (closer to the car body) in the underside exhaust channel than the stock one, not sure if this is due to the bend in it or the smaller cat or because I went with the 2" instead of the 2.5". What this did was once clamped to the adjoining cat-back pipe it lifted the cat-back pipe off the hanger (since the bracket had rusted off it was just laying on the hanger) and made squeaking sounds when it rubbed against the side walls of the hanger when going over bumps. I took this opportunity to do a mufflerectomy and clamped everything in place, so now im running squeak free...
 

IXLR8

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it fits up pretty well, except it sits somewhat higher (closer to the car body) in the underside exhaust channel than the stock one, ...snip...
Thanks, I know Peter went through a lot of effort making sure the original prototypes fit properly. You are the first person I am aware of who has actually installed one of the production ones.
Thank you,
 

n8ronJ

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mk3-
I am going to replicate the repair that you did. Thank you for the explaination of everything. Excellent website for tubing too...

I'm looking at your shopping list from mandrel-bends and you said that 12" would have been fine for that straight section. You are saying then that the section from the transition cone to the joint only requires about 12" of tubing? I'm looking to buy only what I need.

Also, you had the end of the straight section bumped out to 55mm - did that fit the OEM clamp nicely?
 

mk3

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! sorry for the late reply. made last minute plans to go to Taiwan for work - it's where I am now.
Yes, the 55mm expansion fit the clamp well. It's the original diameter for the OEM pipe. I bought a new clamp - I'm uncertain whether a used one will work .. never gave it much thought.
as far as the 12" length being enough... as I said I am out of town... or I could check it. but if I said it then I guess I must have had a reason.... hard to *swear* to it right now though - too much time has passed. The best would be for you to measure it up yourself... it's the person you trust the most;)
 

Kyle_CMU

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Midland, Michigan, USA
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Mine rusted out just behind the cat as well. Can someone tell me how difficult it is to reach the exhaust bolts on the turbo? Please, its cold outside so I only want to lift the car once when I go to do the work.

Thanks.
 

RacerTodd

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Mine rusted out just behind the cat as well. Can someone tell me how difficult it is to reach the exhaust bolts on the turbo? Please, its cold outside so I only want to lift the car once when I go to do the work.
I swapped out my downpipe recently. The three downpipe/turbo nuts are easy to reach from below.

Jack the car up first, make sure it's high enough that you can slide under it easily.

Remove the plastic heat shield over the right inner CV joint (2 bolts).

Now you can reach up and access the three nuts that attach the downpipe to the turbo. The top one closest to the engine is a bit awkward to reach, but doable.
The nuts sit close the downpipe tube. Both a socket on a short extension and a box wrench are generally needed. I've seen both 12mm and 13mm nuts used. Try a 12mm first as if you try to loosen a 12mm with a 13mm socket, you may round off the nuts!
I like to hit them with some penetrating oil first to minimize the chance of snapping off one of the studs.

After the downpipe nuts are off, loosen the two bolts on the clamp at the end of the downpipe. Slide the clamp forwards or backwards so the downpipe is free of the exhaust system.

Last, remove the bracket that attaches the downpipe to the subframe, two 13mm bolts.

Now you can slide the downpipe out. A little twisting and turning is needed, but it comes right out.

Installation is the reverse. Slide it up and in. Install the subrame bracket bolts, then the turbo nuts then the clamp. I use a bit of anti-seize on the turbo nuts to make it easier the next time you remove it. Replace the CV joint heat shield and you're done.
 
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