AVK Flex Pipe Repair

**imnuts** · 09-27-2016 03:10 PM

So, late last week sometime, my exhaust started sounding not so great. I figured it was a flex pipe due to where the leak noise was coming from and the fact that the last time I looked at them, they weren't in great shape. I jacked my car up last night and confirmed that the driver's side flex pipe is indeed bad. It has come completely separated from the crimps/welds and I can freely spin and move it between the two pipes. Thankfully the pipes are still in place and it hasn't dropped, which was my big fear previously. However, I talked to a few people and took it to a shop and they can't replace the flex pipe due to the location, so it's live with it, replace the entire downpipe, or figure out a way to repair it myself.

After looking at the location, I can understand not being able to fix it. The top end is ~2" from the downpipe hanger that bolts to the transmission, and the bottom end is ~3-4" from the bend in the pipe as it goes back the car, so not a great location as there isn't room in either direction really. I'm looking for something that I could repair it short term (<1 year) before I can do a more permanent fix. I want to just replace the entire exhaust as it is nice and rusty from the years of driving through snow, salt, and everything else, and it isn't in the greatest shape. The problem is that I'd get the JHM downpipes and Fast Intentions Cat-Back system to replace it, and $2k for parts plus several hundred in labor isn't really in the cards at the moment.

What I was looking at doing is using either a wrap around exhaust patch to go over the entire length of the flex pipe area, or using a high temperature RTV to seal the ends and glue it all back together. I may possibly do both just to have a stronger seal on the exhaust. Has anyone tried this before? The two things I was looking at are Tiger Patch repair tape or Permatex Exhaust Sealer 80335. Anyone have any experience with either? Any body know a different way to make the repair for <$3-500? Any advice or help would be appreciated.

**Luxus Panzer** · 09-28-2016 05:28 AM

try another shop.

Why not just unbolt down pipe from cat and unbolt at other end...then weld in new flex pipe on bench?

**SJorge3442** · 09-28-2016 07:25 AM

Originally Posted by Luxus Panzer

try another shop.

Why not just unbolt down pipe from cat and unbolt at other end...then weld in new flex pipe on bench?

Unfortunately the DP and cat is the same part on the AVK/3.0 engine. Not to mention they are both a PITA to uninstall.

Mark, I know our flex joints are in a bad spot, but they should totally be weldable by any competent welder/exhaust shop. I'd hit a few more shops up before you give up on the search. I'm not sure if there is a suitable, LEGAL fix for this in the state of PA. I know they are really weird about flexible piping and such on gasoline engines, but they diesels practically do what they want.

**imnuts** · 09-28-2016 02:44 PM

Yeah, I'm not in PA anymore, just moved to Princeton/Lawrenceville NJ area. Not sure of what is around here really, or what shops are good or worth going too. I checked the NJ regional forum and most of that is north of here unfortunately. And yes, removing the downpipe is not something I'll likely be able to accomplish in an apartment complex parking lot, not to mention I'd then need to find a way to weld it.

I'm planning on just getting at least the exhaust repair sealant, maybe not the tape. Then I'll separate it all into 3 pieces, which shouldn't be too difficult since it'll just be taking off a clamp half way back the car to remove the lower portion, clean it up, and glue it back together one piece at a time. Even if it isn't 100%, it'll at least bide me some more time to get it fixed at a different shop. Given the proximity to the transmission though, I'm not sure anyone will be able to weld it properly as there is next to no clearance around the top portion of the pipe.

**seanf86** · 09-29-2016 07:29 AM

Originally Posted by imnuts

Yeah, I'm not in PA anymore, just moved to Princeton/Lawrenceville NJ area. Not sure of what is around here really, or what shops are good or worth going too. I checked the NJ regional forum and most of that is north of here unfortunately. And yes, removing the downpipe is not something I'll likely be able to accomplish in an apartment complex parking lot, not to mention I'd then need to find a way to weld it.

I'm planning on just getting at least the exhaust repair sealant, maybe not the tape. Then I'll separate it all into 3 pieces, which shouldn't be too difficult since it'll just be taking off a clamp half way back the car to remove the lower portion, clean it up, and glue it back together one piece at a time. Even if it isn't 100%, it'll at least bide me some more time to get it fixed at a different shop. Given the proximity to the transmission though, I'm not sure anyone will be able to weld it properly as there is next to no clearance around the top portion of the pipe.

I'm not sure how different the 3.0 is compared to a 2.8 but I had a flex replaced in our old 2.8 auto by a muffler shop, they got a flex pipe that slipped over top of the pipe and clamped the front part and welded the rear. My brothers 2.8 mt we tried using exhaust tape and about 5 min into our drive and shifting from 2nd to 3rd it ripped apart and the leak was back.

**imnuts** · 10-03-2016 03:28 PM

Well, I ordered the Permetex 80335 and it arrived today. I'm waiting on my wire wheel brush to come before tackling the repairs, but I'll post the results when it is finished. Reading the packaging for the Permetex adhesive/sealer, it looks like it is almost meant for repairs similar to what I'm attempting. The directions state to clean up both surfaces, moisten them, put a ~1/2" thick layer of adhesive on the one side and push it into the other, then wait for it to cure 30 min before driving to finish the hardening process. It makes me think it is something like a body adhesive, and reading some of the reviews on Amazon make it sound similar as well. It doesn't need to last forever, but it would be great if it could.

**imnuts** · 10-05-2016 04:18 PM

Since the weather was nice, I tackled the repair when I got home. I cancelled my brush order as it was still pending shipment and i didn't feel like waiting. I should have ordered an exhaust clamp, add mine is in rough shape, so I didn't pull the pipe apart to make repairs.

Using my finger, I would squeeze a little of the sealer on finger and push it into the gap between the pipes. It took maybe 15 min to get both ends and trying to make sure I got it all the way around. The exhaust was still a little warm when I started, so the cure time was fairly short on the one side (<1 min until it was starting to harden), but fine on the other.

I waited about half an hour as directed, then went for a short drive. At first start up, the exhaust leak sound was gone, great sign. I took it fairly easy on the whole drive as I just wanted heat to build in the exhaust. Got home after about 15 min of driving and got out with the car still running to listen for leaks under the car. There is still a very slight exhaust leak sound, but I can't figure out where it's coming from.

I plan on driving it semi gently on my way to and from work tomorrow, then pushing it a little Friday afternoon to see how it sounds and if it's still good. Even if all is well, I may get another tube and put a thin layer over it again in a couple weeks when I can drive it up on ramps and get a better look under the car. In any case, it's $5 well spent so far for the sealer, even if it only lasts 6 months.

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**imnuts** · 10-07-2016 04:26 PM

A few days later, and the repair send to be at least mostly holding. The exhaust leak sound is more noticeable now, but not nearly as bad as what it was with both ends of the flex pipe disconnected. In a few weeks, I'll be visiting family and may try to get it on ramps and check closer as I may have missed a spot on the pipe. Even still, much better than it was, and cheaper than a shop fixing it.

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**SJorge3442** · 10-12-2016 08:08 AM

Originally Posted by imnuts

A few days later, and the repair send to be at least mostly holding. The exhaust leak sound is more noticeable now, but not nearly as bad as what it was with both ends of the flex pipe disconnected. In a few weeks, I'll be visiting family and may try to get it on ramps and check closer as I may have missed a spot on the pipe. Even still, much better than it was, and cheaper than a shop fixing it.

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Any update on this? My 3.0 sprung a leak somewhere and I haven't had a chance to check it out yet. I'll be handling that on Saturday. I always had a small leak on the resonator, and I'm thinking that may have opened up larger now. If so, I am gonna try this stuff as a temp fix while I search around for a plan for replacing the resonator. I'm thinking I may replace it with an X pipe.

**cschuster** · 10-12-2016 10:25 AM

This stuff always happens to everyone around the same time. Not looking forward to removing the p/s downpipe so I'm going to let the flex pipe leak go for a few more months until I pick up a 987.2

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**Spike00513** · 10-12-2016 01:02 PM

An exhaust shop quoted me $200 to weld on new flex-joints.

I bought a good used set for $160 which might be available if I part-out. Found on SearchTempest, there were only 2 others available posted.
Also many 3L-MT's on car-part.
I hear in certain states it's illegal to sell used cats so they'll be reluctant and try to cut it off.

I used AeroKroil on the nuts as prep but nothing else such as temp-shock.
Was sold copper replacements under the claim they're a match. Mistake. Should've re-used the original strong good-fitting ones, or bought replacements.
The copper one mangled the stud, so I bought a used manifold for $10.

Maybe you'll want to get different euro steel manifolds w/ separate-cat piggy-able DP's from eBay Kleinanzeigen.

Originally Posted by SJorge3442

Unfortunately the DP and cat is the same part on the AVK/3.0 engine. Not to mention they are both a PITA to uninstall.

It's not the worst. Done it multiple times. Bottom two bolts from underneath were easy. Top bolt probably required getting a few things out of the way, and wiggling my hand into the open space holding a stubby wrench. IIRC, SlickFix got special extra-height jackstands to pull them on his S4, but I didn't do anything special for mine. After turning/manipulating them, they slid out under the car.
Way harder on automatics.

Originally Posted by SJorge3442

Mark, I know our flex joints are in a bad spot, but they should totally be weldable by any competent welder/exhaust shop. I'd hit a few more shops up before you give up on the search. I'm not sure if there is a suitable, LEGAL fix for this in the state of PA. I know they are really weird about flexible piping and such on gasoline engines, but they diesels practically do what they want.

Some might ask to do it on the car, on a lift, and omit the OE gearbox hangers in the process.

----
my DP<--->catback sleeve clamp connections are leaking. I didn't really clean up the area. A shop recommended I apply an exhaust paste sealant before sliding on the clamp.

Idk why people say buy new ones.
Maybe they're misinterpreting manual instructions "replace" with "purchase new". "replace" just means "put it back" or "reinstall it". If something needs new, it will clearly state it and in a different way more along the lines of "buy new", such as used-up TTY axle bolts.
Instead of buying new hubs, I just clean mine with scotch-brite or roloc.
So why didn't I TLC my sleeve clamp parts? My dremel broke. Sandpaper was futile.

**Nollywood** · 10-12-2016 01:04 PM

The downpipes on the 3.0 are easy to remove on a manual, after removal of the transmission rear brace / crossmember. I would remove it, and get a new flexi welded in.

**Spike00513** · 10-12-2016 01:30 PM

Originally Posted by Nollywood

The downpipes on the 3.0 are easy to remove on a manual, after removal of the transmission rear brace / crossmember. I would remove it, and get a new flexi welded in.

Opinion is subjective. Easy for you to say; you converted your car to manual.
(I agree, so did I)

Pretty sure crossmember removal isn't required to remove the DP. Unless you're saying it makes removal easier, or opens up room to weld a joint still on the car.

**SJorge3442** · 10-12-2016 01:37 PM

Originally Posted by Spike00513

Opinion is subjective. Easy for you to say; you converted your car to manual.
(I agree, so did I)

Pretty sure crossmember removal isn't required to remove the DP. Unless you're saying it makes removal easier, or opens up room to weld a joint still on the car.

Yeah the pipes just arent fun to take off. Its a bunch of tight wrenching and laying under a car in awkward positions. The bottom 2 nuts are the easiest on the DPs, but the top ones are trickier, especially on the passenger side where you need to remove the piping for the air pump. Totally doable, but I would avoid dropping them at all costs.

**imnuts** · 10-12-2016 02:16 PM

Ironic that you bumped this as I was going to post an update. I had my car in for an oil change and they let me come out to look at the repair job I did while it was on the lift draining. The top side of the flex repair is great. Solid as a rock and not budging. The bottom side though cracked the whole way around. I knew there was a leak somewhere, and I found it today. I am going to retry the lower portion of the flex pipe this weekend. It looks like one half pulled away from the other before everything had cured fully as the break isn't even. I also used ~½ the tube on the top portion and maybe ¼ of it on the bottom half, so the top portion is held in place much better to start with. I stopped and picked up another tube from PepBoys on my way home tonight just to have it. The first tube I got from Amazon.

My plan is to jack it up again this weekend and try to clean some of the first attempt material off the lower portion, that is, if I can. The stuff is almost like concrete since it cured, and it isn't to easy to pick at even. Then I'll use a decent amount again on the lower portion, maybe letting it cure longer this time before taking it for a drive. I think the cool air the last time kept it from curing as much as it needed too before I started driving, and it almost blew out. If your flex pipe is as bad as mine was, I'd definitely recommend having 2 tubes on hand and putting as much in the gap as possible.

As far as taking the pipe out and getting a new flex welded in, I don't feel like pulling it myself, and I also don't feel like paying a shop the labor to pull it and fix it. After looking at it again today, it would definitely need pulled to be repaired due to the proximity to the transmission mount. Given that I'm working in an apartment complex parking lot, it's already a big enough headache just trying to patch it while worrying about not getting run over. Also, if the shop was going through the trouble of taking out the downpipe, I'd want the O2 sensor replaced as well, since they're original, and that'd just be another added cost I don't want right now. If patch #2 works, I think this will easily hold up until I have a chance to buy the JHM exhaust items and also a house to swap the stuff out at.

**paul85** · 10-12-2016 02:35 PM

Originally Posted by SJorge3442

Yeah the pipes just arent fun to take off. Its a bunch of tight wrenching and laying under a car in awkward positions. The bottom 2 nuts are the easiest on the DPs, but the top ones are trickier, especially on the passenger side where you need to remove the piping for the air pump. Totally doable, but I would avoid dropping them at all costs.

You don't need to remove the piping for the air pump, but it does make it easier for sure. I just loosened mine to remove the B1S1 02 sensor and was able to get it off without removing the air piping. I used a ratcheting box end wrench and was able to get the nut off that way one tooth at a time..

**JB5** · 10-12-2016 02:55 PM

that's why i went with a 2.7t swap (aside for the added bonus

). taking the downpipes is super easy compared to the 3.0.

**cschuster** · 10-15-2016 10:38 AM

Damn, got to repair now. My eyeballs were vibrating

Tried for 3 hours to get the top bolt off, this is the passenger side and an extra kick in the dick with the sai. No luck so far

**SJorge3442** · 10-17-2016 09:31 AM

Originally Posted by cschuster

Damn, got to repair now. My eyeballs were vibrating

Tried for 3 hours to get the top bolt off, this is the passenger side and an extra kick in the dick with the sai. No luck so far

Damn!

I really hope mines not like that. Really banking on it being the resonator. Those top bolts are no joke and for anyone who says otherwise, well, screw them. They're a bitch. I have so many different tools and its a bitch to get to that nut no matter how to go at it. Its literally a 1/32 turn at a time to get it off. Pretty sure you gotta remove the SAI plumbing in order to get to that top passenger nut. Eitehr way, Im planning on jacking my car up today, so we'll see what it looks like. REALLY hoping its not what you got going on.

**cschuster** · 10-17-2016 09:39 AM

Originally Posted by SJorge3442

Damn!

I really hope mines not like that. Really banking on it being the resonator. Those top bolts are no joke and for anyone who says otherwise, well, screw them. They're a bitch. I have so many different tools and its a bitch to get to that nut no matter how to go at it. Its literally a 1/32 turn at a time to get it off. Pretty sure you gotta remove the SAI plumbing in order to get to that top passenger nut. Eitehr way, Im planning on jacking my car up today, so we'll see what it looks like. REALLY hoping its not what you got going on.

If yours looks like mine, you would know it for sure - its super loud. My eyeballs vibrate between 1200-1800rpm

I had the sai pipe unbolted but still attached. Ran out of time so I'm bringing it to an exhaust shop today with the faint hope they can weld it without removing. No sense wasting more time and bad words.

The manual does say the top nut is accessible from the top with the sai on...it didn't mention anything about needing baby hands and audi special top exhaust nut tool

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**SJorge3442** · 10-17-2016 09:57 AM

Originally Posted by cschuster

If yours looks like mine, you would know it for sure - its super loud. My eyeballs vibrate between 1200-1800rpm

I had the sai pipe unbolted but still attached. Ran out of time so I'm bringing it to an exhaust shop today with the faint hope they can weld it without removing. No sense wasting more time and bad words.

The manual does say the top nut is accessible from the top with the sai on...it didn't mention anything about needing baby hands and audi special top exhaust nut tool

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I believe I had the best shot when using a 1/4" socket and a small(i think 1") extension. Maybe it was the 13mm view through socket. Who knows. really hoping I dont need to drop then. Mines not that bad, just a little louder than it should be and is making a gurgling noise on decel. Nothing bad, just sounds like its pissing air somewhere when im on the gas. Keep us posted with the results from the shop. After looking at your shot, I really cant understand why someone can't weld something.

**deyrag** · 10-17-2016 10:08 AM

Just to add some reference material to this thread. side by side pic of manual vs auto downpipe (both passenger side). Manual is on the left

http://i1292.photobucket.com/albums/...pscmr0xvs3.jpg

**paul85** · 10-17-2016 12:18 PM

I could get a swivel head 1/4 inch ratchet with stubby extension and 13 mm socket on the nut to remove it and put it back on, but the socket kept slipping off when i went to torque it down or initially loosen it. I had to use a box end wrench for that. Done with the SAI on. Taking it off was a lot harder than putting it back on. 15 mins to put all 3 nuts back on and get them tightened down.

**cschuster** · 10-17-2016 12:20 PM

$120 later and I have a new flex pipe. Guy said it was tricky to weld but obviously not impossible.

**SJorge3442** · 10-17-2016 12:52 PM

Originally Posted by cschuster

$120 later and I have a new flex pipe. Guy said it was tricky to weld but obviously not impossible.

Nice. Bet it sounds a lot better!

**imnuts** · 10-17-2016 04:56 PM

Thankfully mine doesn't look like that. I attempted repairing it again last weekend, don't think it worked. Last try will be this coming weekend when I can get my car on ramps. I think I may pick up an exhaust clamp and remove the end of the pipe like I originally wanted too

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**SJorge3442** · 10-17-2016 06:23 PM

I got under my 3.0 today and found all 4 pipes leading in and out of the resonator rotted away. I'll be swinging by an exhaust shop soon to see a out getting an xpipe installed.

I did goop some of the same sealant imnuts used around the front pipes as they looked the worst. Doesn't seem to have helped, so i take it that the rear pipes were leaking

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**cschuster** · 10-17-2016 08:39 PM

For people with manual trans, 120 bucks vs a few hours of frustration is totally worth it. Only 50 bucks or so to be saved after buying the flex pipe and paying someone to weld it anyway.

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**imnuts** · 10-18-2016 07:23 PM

You're still dealing with the frustration of removing it though, which I don't have place that I would feel comfortable doing so. I also don't feel like searching around at this point anymore for a shop since it's 50% and good enough to last until I can just get new everything from the headers back.

**cschuster** · 10-18-2016 10:33 PM

Originally Posted by imnuts

You're still dealing with the frustration of removing it though, which I don't have place that I would feel comfortable doing so. I also don't feel like searching around at this point anymore for a shop since it's 50% and good enough to last until I can just get new everything from the headers back.

Nope. The shop cut/welded it in place. 30 for the pipe and 80 for an hour of labor plus tax

**imnuts** · 10-19-2016 04:03 PM

They have someone with tiny hands or a magic torch on the welder. I can barely get my hands between the transmission and pipe, not sure how they would have ensured it was fully welded on both ends. Glad it was a simple fix though.

**Spike00513** · 11-04-2016 01:39 AM

Selling mine if anyone is interested. Relevant thread, figured I'd post here.

**Protection** · 11-04-2016 07:13 AM

Replacing the downpipes on an auto is a major pain in the arse. There is NO way to remove the pipes without supporting the engine, dropping the subframe and removing the axles and tranny mounts. There is just not physically enough space to slide the cat out. I did this nightmare job two weeks ago. I removed the SAI pipe to get the top nut off on the passenger's side and with the subframe lowered the bottom nuts are easy.

My pipe from the flex joint back was completely missing--bought the car that way.

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**SJorge3442** · 11-04-2016 07:22 AM

Originally Posted by Protection

Replacing the downpipes on an auto is a major pain in the arse. There is NO way to remove the pipes without supporting the engine, dropping the subframe and removing the axles and tranny mounts. There is just not physically enough space to slide the cat out. I did this nightmare job two weeks ago. I removed the SAI pipe to get the top nut off on the passenger's side and with the subframe lowered the bottom nuts are easy.

My pipe from the flex joint back was completely missing--bought the car that way.

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Did you really need to drop the subframe though? If the car was high enough in the air, I would think the pipe would slide out after bending it around a bit, especially with the axles removed. I for one like removing the axles for this job so that its easier to work in there. Also, the bottom manifold/dp nuts are really easy to get to on a manual with a universal joint on the end of a socket. Pair that with an electric impact gun and you got yourself two easy nuts to get off.

**Protection** · 11-04-2016 07:46 AM

Yes, dropping the subframe is not optional. I wasted hours wiggling, twisting, removing parts before I came to the cold hard conclusion that subframe had to be lowered. I also found a U.K. Website saying the same--impossible w/o dropping subframe. The auto tranny is just too fat. Compared to the rest of process, the bolts holding the downpipe to the exhaust manifold are easy peasy--or at least in my case they were.

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**SJorge3442** · 11-04-2016 08:02 AM

Originally Posted by Protection

Yes, dropping the subframe is not optional. I wasted hours wiggling, twisting, removing parts before I came to the cold hard conclusion that subframe had to be lowered. I also found a U.K. Website saying the same--impossible w/o dropping subframe. The auto tranny is just too fat. Compared to the rest of process, the bolts holding the downpipe to the exhaust manifold are easy peasy--or at least in my case they were.

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Thats good info to have on here! Also more encouragement to do a TIP-6 speed swap while you fix this!

**imnuts** · 11-11-2016 09:23 AM

Went to a local exhaust shop. Both flex pipes were leaking, obviously the driver's side was worse. The clamps that connect the downpipes to the catback portion were also leaking. Getting it all fixed right now for ~$400 total.

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