Crack in Muffler

Crack in Muffler

I was told I have a crack in my muffler by an A&P that I trust.  I took a look and just can't find any crack.  I did not take the cabin heat - shield off and neither did he.  Is there any specific method of looking for cracks and where do they usually form?

I see no corrosion, but understand that many cracked mufflers are due to vibration (fatigue cracks).  Any comments?

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Re: Crack in Muffler

Go back to your mechanic and have him point out the crack.

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Re: Crack in Muffler

Clay,  That would be way too easy!   

It's a logistics thing.  I heard about the crack late Friday and I can't meet with him until next Friday at best as I'm out of town all week.  So, I was hoping for some insights over what was left of the weekend.

I spoke with him today and he told me the crack is on the bottom of the muffler in the vicinity of where the exhaust pipe enters the muffler. He noticed gases coming out after running the engine.

OK so the big question is do I replace it with an identical muffler or add a Powerflow exhaust, ohh no, pretend I never said that! (ha!)
I'll go read the old posts!

Does anyone know whether a crack can be repaired in a muffler or is that just asking for trouble? Would any competent A&P sign off such a repair or does it depend?  If so on what?

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Re: Crack in Muffler

Call Aerospace Welding (Minnesota)  They are faa certified and I have found them to be of excellent quality.  You can save a core charge by exchanging your old one,  plus,  the one they send you will be brand new.  I would start there if your is proven to be cracked. NOTE* Unless you have someone who is "certified" specifically to weld aircraft exhaust systems, I wouldn't go there...

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Re: Crack in Muffler

I had a crack similar to what you described.
My mechanic had me take it to a reputable welding shop.
It's stainless steel..MIG welded?...The mechanic inspected
it prior to puting it back on.  A logbook entry was made.
The inspector checked out the repair during the annual.
I think the welding shop charged $11/inch for the weld.
It was about $25 for the repair...$ub$tantially less than
the cost of a new muffler.
Michael

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Re: Crack in Muffler

"the mechanic inspected it prior to putting it back on" ?? Most mechanics are not skilled in the area of inspecting somebody elses welding repairs.  AC 43.13-1B para 8-50 states - "welded repairs to exhaust systems are complicated by the difficulty of accurately identifying the base metal so that proper repair material can be selected.  Changes in composition and grain structure of the original base metal further complicates the repair"  How can your mechanic inspect somebody elses repair when he knows nothing about what took place during that welding process.  A reputable welding shop is nice but they most likely  lack the expertise in welding aircraft exhaust systems.. Let the folks who are knowledgeable in the process do the repairs.. The certification tag that goes with the repair is what I would rather see in the Logbook....

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Re: Crack in Muffler

Barry,

If you do indeed have a crack, I have an extra exaust system that was removed from my plane with only 40 hours total time on it since new.  I too had a crack and replaced my muffler then I replaced it with the tuned exaust.  Please email me as it might be cheaper to replace than weld.

Curt Fargo

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Re: Crack in Muffler

Curt,

See your e-mail

Barry

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Re: Crack in Muffler

Thanks all for the help.

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Re: Crack in Muffler

Jack,
You're absolutely right.
I guess that explains why my A&P had me take the
muffler to a specific shop and a specific person who
experience with aircraft mufflers, and not to a friend
of  mine that offered to do it for free.
Apparantly my A&P did have some welding skils, as
he had built a couple of planes from scratch.
I feel fortunate to have had him as a personal friend
prior to my becoming a pilot/owner.
I suppose my circumstances were a bit unique and
most A&Ps would have me done exactly what you
stated.
Michael

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Re: Crack in Muffler

Epilog....

The muffler has been replaced with a new SS muffler obtained from Aerospace Welding (Minnesota) (Thanks Jack).

Turns out the crack could not be repaired without a substantial amount of work.  The crack was not visible because it was hidden.  There is an extra-piece of material used to support the joint between the large exhaust pipe (that is in the air stream) and the muffler.  The way the A&P knew it was cracked is that he observed exhaust gas stains on outside of the support material, clearly where there should be no exhaust.  In the old muffler there are two small holes in the outside support material that allows the welding gasses to escape.  The exhuast stains were around this area.

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Re: Crack in Muffler

Sounds like you have a very good mechanic.  Buy him a six pack of his favorite beverage.

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Re: Crack in Muffler

Cracked mufflers are serious business.  I put a beautifully restored C170 into the ocean recently, after a cracked muffler choked off my intake low over the city and all went quiet...  I would recommend taking all necessary precautions when dealing with a cracked exhaust system, to avoid much larger problems... smile

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