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Need a muffler - some help (and don't have your shop try to weld your muffler)


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Well --- ladies and gentleman, I just had a frustrating day at the shop: most recently I noticed a slight PPM of carbon monoxide in the cabin with the heater on. In cruise flight, it would stay under 10PPM with the heat on. I made a thread about it here: 

I was in the shop and decided to leak test the muffler. We found a very small crack:

455500566_image1(3).thumb.jpeg.f8cfb759c74561629c6dcbc5d362e26d.jpeg

It was about 2pm at this point and I asked my mechanic this could be fixed easily and he said he could probably weld it and took the exhaust off. Well, a few minutes into the welding, holes started to form. We tried to fix them and ended up spending 3 hours chasing ever larger leaks.

We almost gave up, but decided to try one more hail mary:

1981266177_image2(1).thumb.jpeg.7e93dbf6011ffd4433666cdd912825fb.jpeg

Here is where we gave up after about 3 hours of welding and testing, repeating, taking the metal off, putting new on, etc:
1960838739_image3(2).thumb.jpeg.c792c481e71e25fb935d6c7d6b8dd238.jpeg

Well now, my muffler is definitely unairworthy and I need a new one. The rest of the stacks look good, but where the hell can I get a muffler. Apparently it's not that easy...any leads/advice? I called Knisley but they can only sell me their system, Acorn welding wanted $1600 to potentially weld the exhaust. I'm not sure if anyone else has any suggestions?

Bummer, I was planning to fly the Mooney to Providence tomorrow too. Not sure what the lesson here is (don't try to chase a small crack? or maybe this is a blessing in disguise), but either way, next time your mechanic wants to weld your muffler: SAY NO!

 

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Is it possible to take the muffler to someone that's good with a TIG welder? I could be wrong, but judging from the pictures, that repair didn't look like it was ever going to come out very well with that patch and lack of surface prep.

Edited by David_H
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It is widely recommended to never attempt exhaust system repairs at the shop, and this is also taught in A&P school. Not very cool that they attempted and now it may no longer be repairable...  Yes, send it to a repair station that specializes in exhaust repair... if they say not repairable, maybe Alan (Grim Reaper) can help with a replacement?

Edited by PilotCoyote
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AWI worked well for me. they will need the risers as well. My shop will weld exhaust routinely, but at a certain point the wall is so thin it will blow through next to the weld. which was happening to mine. I was doing a weld repair every oil change....... finally I got tired of that! $2k and AWI made new everything. And It fell right into place. 

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Don't despair of having it repaired.  My understanding is that they can "repair" almost anything for exhaust (talk to the aftermarket turbo guys on that one).  As long as they use one part of the original system it is considered a "rebuilt" system.  WAY cheaper than a new one.

But then again, there's always the powerflow...  ;)  <Cracks open can of worms, steps back to watch>

Edited by cctsurf
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17 minutes ago, AlexLev said:

Approx how much was the AWI repair?

 

2 hours ago, tangogawd said:

..... finally I got tired of that! $2k and AWI made new everything. And It fell right into place. 

For just the muffler I’d guess 700-850 especially when you add shipping both ways.  From what I see in the pictures it looks more like a complete rebuild of the muffler vs a patch job. However, also understand there is a chance if you send the complete system other parts might be really thin in areas...

Edited by MIm20c
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2 hours ago, cctsurf said:

Don't despair of having it repaired.  My understanding is that they can "repair" almost anything for exhaust (talk to the aftermarket turbo guys on that one).  As long as they use one part of the original system it is considered a "rebuilt" system.  WAY cheaper than a new one.

But then again, there's always the powerflow...  ;)  <Cracks open can of worms, steps back to watch>

AWI told me to send them a tailpipe flange and they can “repair” the rest from that one part.

Clarence

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Anyone know part # for this muffler? The parts manual for the M20G says 630060-001:

1738835012_ScreenShot2019-03-15at11_57_51PM.thumb.png.7ba4ed29e80e9896cffa961171a3ba5d.png

 

However, this site below says M20G is 630105-501 (which is also what that eBay listing above says), so I am not entirely sure:

 https://www.aviall.com/medias/0464.pdf?context=bWFzdGVyfHBkZnwxMDEwMzg5fGFwcGxpY2F0aW9uL3BkZnxwZGYvaDZiL2gzYi84ODE0MDgzNDQwNjcwLnBkZnwyYWM2MzQ3NGMyOTA0YWNhY2E5NmU4YTk5Mjc0M2U0NzViZGQxMjgyMzhiNmU2N2MwMDFhNTE1MmIzNTcwNzBl&attachment=true

(ah, at a closer look it looks like serial #'s 69000 and above for the M20G might be -501, while mine is still in the 68000s, so I am probably -001). I wonder if AMI may have it in stock: https://awi-ami.com/mooney-180-ball-rib-muffler-630060-001.html - will try to call them on Monday.

Edited by AlexLev
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3 hours ago, M20Doc said:

This might help.  Note 2 drives you to the -501 muffler.

 

AE7F4A8C-E671-4C10-B0D1-A8A20751E6EB.jpeg

61DEA4C8-EDB7-4EC2-9432-696F70B27097.jpeg

0B72169C-244B-4CF1-93DB-74FB0FFAAF71.jpeg

Thanks, I think mine would still be the -001 since if I'm interpreting note 2 correctly, it's saying aircraft after serial # 69000 get the -005 replacement.

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5 minutes ago, Yetti said:

I can't weld, but whoever was trying to weld yours, can't weld either.   Looks like too much heat and wrong size rod/wire

Yeah, at first he was using a thin piece of metal and that large piece of sheetmetal was more of a hail mary after 3-4 attempts of welding/testing for leaks, etc, but he burned a few holes claiming the exhaust was already really thin and in bad shape, but he could have just been using too much heat. Honestly, the initial crack was so tiny and I had such a small leak a little bit of JB Weld might have done the trick at least for a little while.

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16 hours ago, RLCarter said:

Heli-Arc (TIG) is where it's at when it comes to thin material. I thought exhaust were a SS alloy, it still might be repairable but it would have been easier before the 1st attemp

 

16 hours ago, David_H said:

Is it possible to take the muffler to someone that's good with a TIG welder? I could be wrong, but judging from the pictures, that repair didn't look like it was ever going to come out very well with that patch and lack of surface prep.

 

8 minutes ago, Yetti said:

I can't weld, but whoever was trying to weld yours, can't weld either.   Looks like too much heat and wrong size rod/wire

I've worked in the metal trade around welders my entire adult life and not even the best of them would recommend repairing that thin metal without TIG or MIG. Yes, there are shops/welders out there that would be able to repair, even in its current state.

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1 hour ago, AlexLev said:

Thanks, I think mine would still be the -001 since if I'm interpreting note 2 correctly, it's saying aircraft after serial # 69000 get the -005 replacement.

I would interpret it as used on the serial numbers per note 2 and as replacement for earlier serial numbers.

Clarence

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Welding or gluing....

Exhaust system metal might be made from some high end metals... like Inconel.... probably adds to the challenge of welding properly...

 

Either way, in the past...

small cracks have turned into long tears in a single flight...

small amounts of CO, turned into too much CO...

Often, CO is not detectable by the person being poisoned...

So... even if JB weld could block the hole, it won’t be able to stop a crack from propagating... it doesn’t have the strength or adhesion to do so...

Compare the costs...

  • a proper fix.
  • broken plane, still needing a proper muffler fix.

Either way, the cost seems to have been incurred already.

Next steps seem to be getting the muffler OH’d at the lowest cost...  typical muffler OHs are done by a couple of exhaust welding shops... the procedure is two step...

  • replace the front half parts... then...
  • replace the back half parts...

It looks totally brand new when they are done.   :)

Working with ancient sheet metal that is in a hot environment can have a lot of wear...over 50years... flame tubes typically break down first, and the hottest spots move to places that aren’t built to be that heat resistant...

If you can’t find the flame tubes, they may have departed the plane already...

If able... or when able... get a new muffler, or a muffler OH...

At the point you have measured an increase of CO related to the heater... it has become time to enact plan B...

stop playing with Fire, er CO....

This is sample logic that can be used to free up the necessary funds to improve the safety level of one’s Mooney...

PP thoughts only, not a mechanic...

Best regards,

-a-

 

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