Thoughts on this exhaust repair?

[JHZR2]

My 2008 ML320 had a cracked flange clamp. It was a female-male flange.

I changed the clamp but it didn’t matter. The one side of the pipe was cracking at least 180 degrees around and so it needed a repair.

I took it to a local shop that I’ve been pretty happy with for other small jobs. They did this:

Three issues I see. One is that the OD of the repair piece the not stretched seems smaller than the OE pipe. It’s only a few inches, but I suspect the flange is also smaller. Is this enough to be concerned with?

The second is the use of the red sealant. Is this necessary? I’d assume they would have a perfect set of flanges, square to each otber, and weld the pipe ends that way. So why use sealant? I don’t really care, I don’t think, just seems unnecessary with the black gasket in the sandwich.

Final is the hardware. I thought flanges like this used longer bolts with springs. They just used locking flange bolts. Granted the OE connection was just a “friction mate up” with a clamp.

Should I be concerned?

Good thing is that any exhaust that was leaking out before (never heard or smelled it) is now definitely not. And I drive for economy, so I don’t know that any restrictions would really matter much anyway. If I get 390 or 400 ft-lbs not sure I care. But should I?

 

[PontiacHO]

That was a “around your elbow” kind of way to repair. You would have been better off to have had one pipe as a splice and two welds without the flanges and RTV squishing gaskets.

 

[dogememe]

Why not just use one piece of pipe, why even put a flange there, or am I missing something?

 

[JHZR2]

That was a “around your elbow” kind of way to repair. You would have been better off to have had one pipe as a splice and two welds without the flanges and RTV squishing gaskets.

Why not just use one piece of pipe, why even put a flange there, or am I missing something?

So… I asked for the flange. The shop originally recommended doing exactly as you say.

The OE system had a connection there. Having a connection there allows for removal of the first muffler and the DPF (there’s no other emissions besides DPF), which also allows the engine mount to be easily accessed and replaced (which I think I may need to do at some point.

Maybe it was a mistake, but I wanted the ability to break the system there.

 

[meep]

I’d be fine with it. It could cause some cracking elsewhere IF the original joint allowed some flex. If it didn’t, I’d just move along. They did clean work for what it is.

 

[bdcardinal]

Looks like Ray Charles did the welding.

 

[Hall]

The smaller diameter pipe is inconsequential for that short amount of length. Not sure why they needed the red sealant as it appears there's a gasket in between the flanges.

The hardware ? Nuts and bolts are completely normal. Spring bolts are available but not mandatory. Swap them yourself with spring bolts or at least SS hardware before those rust and seize in place.

How much did they charge ? Years ago, that might have been a $50 cash job but curious what it would be today....

 

[JHZR2]

Looks like Ray Charles did the welding.

Better than if I did it (I don’t know how).

 

[JHZR2]

The smaller diameter pipe is inconsequential for that short amount of length. Not sure why they needed the red sealant as it appears there's a gasket in between the flanges.

The hardware ? Nuts and bolts are completely normal. Spring bolts are available but not mandatory. Swap them yourself with spring bolts or at least SS hardware before those rust and seize in place.

How much did they charge ? Years ago, that might have been a $50 cash job but curious what it would be today....

$135 just to cut and weld in metal. The flanges were like $18, gasket was similar. I left the receipt in the car. I think with tax it was around $200.

Better than me going under the car with a sawzall. I was tempted to…. But I don’t have a welder or know how to weld. Might I have gotten a different type/size of interfacing pipe? Sure. But I would have spent hours.

So unless it was going to cause any concerns, I’m good. I will pull a bolt at some point and swap them. I think that’s good practice. Thanks!

 

[slacktide_bitog]

Do people still use a can of soup for that kind of repair?

 

[JHZR2]

Do people still use a can of soup for that kind of repair?

Not sure it would have worked on this.

The sealant seeped through the cracked section.

 

[RBT]

It is a functional repair and perfectly acceptable for a 17 year old car. I cannot tell if the hardware is stainless. If it isn’t, change it before it rusts in place or you will undermine the purpose of allowing the exhaust to be split at that point.

 

[ka9mnx]

I think they did an excellent job.

 

[cptbarkey]

How does the weld look on this part? Looks a little suspect but could also be the angle.

Welding pipe is difficult.

 

[eljefino]

You don't need stainless hardware. If it's a 5/16" bolt and it gets too rusty you can just put about a foot extension on it and shear it off.

Spring bolts are for exhaust connections with "packing", either sintered iron "donuts", graphite rings, etc that lose bulk over time and need the springs to take up the slack. They might also be used in situations where there might be a degree or two of flex required.

I'm with you on the sealant. Shouldn't be needed on a clean new flange. I like "toyota style" donut gaskets-- they start at about 1/4" thickness and have more crush than normal gaskets. They can be finagled into place with a couple supportive screwdrivers while the hardware is torqued, or, shudder, tacked into place with orange RTV.

That all said you got a good price and the welds look good from my house.

 

[JHZR2]

How does the weld look on this part? Looks a little suspect but could also be the angle.

Welding pipe is difficult.

View attachment 301782

He did that off the vehicle.

No signs of leaks. Since it’s a diesel, if there is any leakage I’ll see a trail of black soot before much use. I’ll keep an eye on it.

 

[JavierH19]

I've seen far worse that still worked fine.

 

[f355spider]

I would inspect your exhaust hangers. If they are rubber or have rubber inserts, as they get to this age, then can have less elasticity and when that happens, the stress goes to the pipe instead. So if they are hard and inflexible...might be worth replacing them?

 

[JHZR2]

I would inspect your exhaust hangers. If they are rubber or have rubber inserts, as they get to this age, then can have less elasticity and when that happens, the stress goes to the pipe instead. So if they are hard and inflexible...might be worth replacing them?

Good point - I didn’t see anything out of the ordinary when I’ve been under the car. It’s a different hanging and support system than my collection of classic MB cars, probably worth a closer look.

 

[The_Eric]

The repair is just fine. Both sections of pipe are probably just the same size as the original front and rear factory pipes, just expanded up to provide a slip fit, and if it is a tiny bit smaller, then no biggie. It's not like your car was engineered to within an inch of its life for maximum performance. The sealant is just because everyone is paranoid about comebacks and bad Internet reviews.

Just like a couple of others have said, the only nitpick would be to replace the carbon steel bolts with stainless - not because you want to be able to get them apart (as eljefino said, if they're seized, just break em) but so they don't rot out and break on their own.