Muffler crack

[Spurious Moppet]

11 minutes ago, takair said:

I’m curious, did you shut heat off and continue to get CO?  You may want to check the heater box seals as well.  Many leak as they age and then you have no way of isolating.  When they leak, you feel heat year round....so added benefits in summer.

Good idea. I did make sure it was closed but I will check the seals. I had been thinking the air was too warm even with the heat off. Can’t believe I didn’t see the danger there.

I called Dawley and Knisley and they were both a month for overhaul. AWI said about a week and $1020. I’m sending the risers as well so they fit.

[DanM20C]

41 minutes ago, jaylw314 said:

You wouldn't see that at annual, though, unless you cut open the muffler can.  It would be nice if there was a way to detect impending heater failure

The heat shroud around the muffler should be removed every annual and the muffler should be inspected.  Preferably under low pressure and soap and water looking for bubbles. No need for cutting.

A Sensorcon or other similar low level detector is a good tool to catch an impending muffler failure.  I test the heater for CO on every flight by holding the Sensorcon in front of the heat vent and look for changes with it on and off.

@Frozen Flying I'm glad my little field trip encourage you to get a detector and saved you from a similar (or worse) fate.  Thanks for sharing!

Cheers,

Dan

[Guest]

1 hour ago, jaylw314 said:

You wouldn't see that at annual, though, unless you cut open the muffler can.  It would be nice if there was a way to detect impending heater failure

@Frozen Flying, out of curiousity, do you use LOP or ROP for cruise?

Less than half a dozen screws will allow you to open the heater jacket and see the muffler.  No need to cut anything open.

Clarence

[Guest]

27 minutes ago, DanM20C said:

The heat shroud around the muffler should be removed every annual and the muffler should be inspected.  Preferably under low pressure and soap and water looking for bubbles. No need for cutting.

A Sensorcon or other similar low level detector is a good tool to catch an impending muffler failure.  I test the heater for CO on every flight by holding the Sensorcon in front of the heat vent and look for changes with it on and off.

@Frozen Flying I'm glad my little field trip encourage you to get a detector and saved you from a similar (or worse) fate.  Thanks for sharing!

Cheers,

Dan

We have an old Filter Queen vacuum cleaner in the shop dedicated to pressure checking exhaust systems.  Everyone should should be having this done during their annual.

Clarence

[jaylw314]

27 minutes ago, M20Doc said:

Less than half a dozen screws will allow you to open the heater jacket and see the muffler.  No need to cut anything open.

Clarence

Learn something new every day, the picture makes it look like it had been cut open so I assumed wrong...

[Raptor05121]

What is everyone paying for exhaust overhauls? Is it worth the price delta to go PowerFlow?

[J0nathan225]

3 hours ago, DanM20C said:

@Frozen Flying, I'm so glad you made it down safely!  Another save from a CO detector. 

This is a good time to plug the detectors that are offering discounts. 

Guardian has offered a 20% discount on all their CO products.  It's very generous and may not last much longer. 

Code: coaware

Sensorcon makes an excellent portable and they still have the 20% discount code active.

Code: aircraft2017

I like redundancy so I have a Guardian, and 2 Sensorcons

Cheers,

Dan

Just ordered the Sensorcon, thanks for this.

Glad Frozen flying made it down safely. 

[Bob_Belville]

5 minutes ago, Raptor05121 said:

What is everyone paying for exhaust overhauls? Is it worth the price delta to go PowerFlow?

The PFS is much more expensive. When I did mine 6 years ago it was at least double the overhaul cost. I thought it was worth it as a more permanent solution with a bonus of a performance boost. The PFS is more robust and should outlive conventional mufflers. The school C172 here got less than 500 hours out of standard mufflers and over 2000 out of the PFS.

But of course the pay back is over several years... 

[gsxrpilot]

1 hour ago, Raptor05121 said:

What is everyone paying for exhaust overhauls? Is it worth the price delta to go PowerFlow?

Reach out to @jasona900. He knows a think or two about PowerFlow and where it works best.

[carusoam]

4 hours ago, jaylw314 said:

You wouldn't see that at annual, though, unless you cut open the muffler can.  It would be nice if there was a way to detect impending heater failure.

Jay, (never mind... M20Doc already gave you this insight... and more...)

at annual the heat shroud comes off, and exposes that outer surface of the muffler...

the thread looking rods are the spacers for the heater shroud...

I believe we are looking at that surface with the crack... 

 

The interest in knowing if the heat was on or off is because that crack is leaking into the hot air stream.

Our heat systems aren’t perfectly sealed. So once CO starts to leak through a crack it is going to start showing up on the CO monitor...

definitely more when the heat is on.  So if CO shows up on the monitor.  Close off the heater.  Land and figure it out on the ground...

The challenge with CO poisoning is it interrupts the thought process... making it more difficult to recognize what has gone awry...

We have no method to measure how much CO we have absorbed in our blood stream while flying...  the oximeters/oxygen sensors we use to prevent issues at altitude are confused by the CO...

As far as time to do something... Dan went from take-off to sleeping, in the climb... not much time to experiment...

Heat off, LOP, Carson’s speed/low power, low RPM... all things that would help convert more CO in the direction of CO2.

PP thoughts only. Not a sensor guru... a few minutes in my now classic Firebird... the CO level goes ballistic... so much for the new exhaust system it got... it appears CO leaking in front of you is going to find it’s way in... work on all those seals.... 

Best regards,

-a-

[jasona900]

1 hour ago, gsxrpilot said:

Reach out to @jasona900. He knows a think or two about PowerFlow and where it works best.

I worked for Power Flow during and after college (1998-2001), just as the company was getting started.  I did a lot of test flying on their C172, 177, and Piper exhaust systems.  I assure you there was a noticeable increase in performance on the O-320 and O-360 powered airplanes.  We flew hundreds of hours testing different exhaust configurations, and even more to ensure the FAA STC requirements were met.  We strived to provide a quality and reliable  product.  Of all the test flights I flew, I can assure you that when compared to the stock exhaust system, there was more power on takeoff with shorter take-off runs, better climb performance, and lower CHTs in cruise.  This was not a "seat of the pants" measurement.. we always flew with a co-pilot who would document each test flight.   

We had a Piper Arrow that we conducted several tests on.  This was the only fuel injected airplane equipped with a PFS system I got to fly on.  Not sure if the constant speed prop "absorbed" the power gain, but the documented performance gains were not there.  What was there was a decrease in fuel flow when compared to identical power settings with a stock exhaust, and lower CHTs.  I left the company before they came out with any of their Mooney products.

Fast forward (whoa) 15 years, and I had my own M20C that failed an exhaust pressure test during annual.  Rather than re-welding/rebuilding for $1500, I decided to go with a PFS.  The customer service had not changed since I worked there (excellent) and I had a new PFS installed on N6XM in no time.   Similar to my experience with the Arrow, I did notice lower fuel flows, and MUCH cooler CHTs (around 15+ degrees cooler on each cylinder), but that seat of the pants increase in power was not there.   Unfortunately, N6XM met an untimely demise with a landing gear collapse due to an incorrect preload setting during annual, so I did not get a good data set for comparison.

Back to this thread... carbon monoxide poisoning simply should not happen with a PFS.  There are no welds in the heat exchanger section to leak.  That alone, along with the benefits of cooler CHTs, lower fuel flows, and a possible increase in HP make it a no brainier for me.  If the time comes to fix the exhaust on the J model I now own, I will once again forego the $1500 and put my name in line for a PFS.

[carusoam]

Very interesting chain of experiences, Jason.

Thanks for sharing the observation related to the weld, and no weld on the PFS...

That surely is an interesting thing to look into.

Best regards,

-a-

[Spurious Moppet]

On 11/7/2018 at 4:23 PM, takair said:

I’m curious, did you shut heat off and continue to get CO?  You may want to check the heater box seals as well.  Many leak as they age and then you have no way of isolating.  When they leak, you feel heat year round....so added benefits in summer.

I’ve got the old slider style heater box valve not the newer flap type (1966 E). Looking at the parts manual I don’t see any seals listed in the heater box. Anyone know how to improve the ability to shut off the hot air in the slider type? The mechanic that has the plane right now said the valve works normally but I know it has felt like hot air still is getting by.

[takair]

7 minutes ago, Frozen Flying said:

I’ve got the old slider style heater box valve not the newer flap type (1966 E). Looking at the parts manual I don’t see any seals listed in the heater box. Anyone know how to improve the ability to shut off the hot air in the slider type? The mechanic that has the plane right now said the valve works normally but I know it has felt like hot air still is getting by.

Hmm, interesting.  Mine is older than yours (64) and I have a rotating flap heater on the engine side of the firewall and a slider for fresh air on the cabin side.  My friends 63 C has a slider, like you describe, on the firewall side.  Be sure your mechanic is looking at the right valve...

[carusoam]

65C had two slide valves that would get dirty in a year’s time. Clean and lubricate to keep them working.

One valve for hot air, the other for outside air...

The rotating valve was a vast improvement in sealing out the the unwanted airflow... with rubber...

Best regards,

-a-

[Spurious Moppet]

27 minutes ago, takair said:

Hmm, interesting.  Mine is older than yours (64) and I have a rotating flap heater on the engine side of the firewall and a slider for fresh air on the cabin side.  My friends 63 C has a slider, like you describe, on the firewall side.  Be sure your mechanic is looking at the right valve...

Ok I just took a closer look at the parts manual and I should have a flap type valve on the forward side of the firewall as you said. That has a seal P/N 640047-013 it looks like. Here is the link on LASAR: https://lasar.com/baffle-baffle-seals/seal-640047-013?rq=640047

It looks like a circular piece.  Does that make sense? I’d go check the plane but it’s far away.

[Bob_Belville]

6 minutes ago, Frozen Flying said:

Ok I just took a closer look at the parts manual and I should have a flap type valve on the forward side of the firewall as you said. That has a seal P/N 640047-013 it looks like. Here is the link on LASAR: https://lasar.com/baffle-baffle-seals/seal-640047-013?rq=640047

It looks like a circular piece.  Does that make sense? I’d go check the plane but it’s far away.

Yes, it is inside a ss box with scat hose coming from muffler shroud. There's an arm on the side that moves the flapper via the heat cable from the cabin. The box has a smaller scat hose that allows the hot air from the muffler shroud to vent overboard when the heater flapper is closed.  

[N201MKTurbo]

On 11/7/2018 at 2:05 PM, thinwing said:

Ok ,at that percentage (though not good)symptoms would be slight headache after 2 or 3 hours of exposure and death would be unlikely for typical E fuel duration flight.Glad you are ok

I have to agree with this assessment. When I had my CO issue I had a giant crack in my muffler. The gap was 1/8 inch wide and 3 inches long. I flew with it like that with the heater on full blast for almost two hours. I had more than a slight headache, it was a wicked headache. I bought a CO spot sensor from the FBO at my destination and put it by the heater outlet and it immediately turned dark black. I turned the heater off and the CO spot turned back to its normal color. I know I'm going to catch hell for this, I was young and stupid at the time, this was in '85, but I flew the plane home IFR with the heater off. The bracing cold kept me alert and I didn't have any change in symptoms on the way home. It was below zero in the ground and I flew home with all the air vents open. I was shivering severely the whole way home. I figure the CO level coming out of the heater duct was 1000 ppm or so. I always kept the overhead vents open some so the levels I was breathing were a bit less. 

The symptoms came on very gradually. It wasn't until the last 1/2 hour of the trip that I thought  there must be something wrong. At that point I turned off the heater an put on my jacket.

[N201MKTurbo]

BTW,

You don't need the muffler overhauled. Any A&P is legal to weld it. I would find an an aviation welder and just have him fix the crack. As an A&P I would just find a good TIG welder and supervise him doing it. Shouldn't be more than $100 or so, or a few beers if you know them well enough...

[Ragsf15e]

Scary.  I’m buying sensorcon right now.  Thanks for sharing.

[Robert C.]

Great thread! My muffler went out for repair 1 week before this showed up, if I'd known I would have asked the shop why they didn't do the welding themselves. Muffler repair shops do seem to be busy, I was told I could get a repaired one in a week but at more than twice the price of them fixing mine which might take 3-8 weeks given the back log. Given that the annual was going on and I'm grounded while my ulcer heals I decided to take my chances on the wait and save some money

[Guest]

On 11/10/2018 at 1:02 PM, Robert C. said:

Great thread! My muffler went out for repair 1 week before this showed up, if I'd known I would have asked the shop why they didn't do the welding themselves. Muffler repair shops do seem to be busy, I was told I could get a repaired one in a week but at more than twice the price of them fixing mine which might take 3-8 weeks given the back log. Given that the annual was going on and I'm grounded while my ulcer heals I decided to take my chances on the wait and save some money

Unless your maintenance shop has a certified welder on staff, sending it to someone who’s does is the correct choice.

Clarence

[cliffy]

I just bought my Sensorcon too!   20% off just like mentioned!

[Shadrach]

On 11/9/2018 at 2:21 PM, N201MKTurbo said:

BTW,

You don't need the muffler overhauled. Any A&P is legal to weld it. I would find an an aviation welder and just have him fix the crack. As an A&P I would just find a good TIG welder and supervise him doing it. Shouldn't be more than $100 or so, or a few beers if you know them well enough...

Thank you for stating this Rich. I am pretty sure a non credentialed individual such as myself would have been flamed for making such a statement. That muffler appears perfectly repairable.  It seems ridiculous to take it out of service for a month and spend over a 1000 on an overhaul.

[Shadrach]

14 hours ago, M20Doc said:

Unless your maintenance shop has a certified welder on staff, sending it to someone who’s does is the correct choice.

Clarence

Are you suggesting that an AI is not legally able to determine that a weld has been performed IAW standards acceptable to the administrator?  It's a genuine question. By certified do you mean FAA certified? I don't know of any reg that requires an "aerospace welder", but there's a lot of regs I am unfamiliar with and or interpret differently than some of the more conservative IAs.  I know it's an airplane part, but were talking about a steel can that needs to be cleaned inspected and repaired. The affected area appears to need no more than a 3" bead.  A good MIG guy with a pencil grinder could knock that out in minutes not hours.

Edited November 12, 2018 by Shadrach