2003 M7-235-C.... left muffler has developed a hole - looks like an irregular bullet hole shot from the inside... also have a hole in the carb heat shroud and melted the gelcoat off of the fiberglass on the lower cowl...
1. What would have caused that?
2. What's this likely to cost for muffler parts?
... the joys of aviation (and its ceaseless maintenance)...
Thanks in advance for your help!
M7-235-C Muffler Question
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TK Nashville
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Green Hornet
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Cantact Bryan Horn at Maule he can fix you up with a price but ball park if memory serves the metal sleeve shrouds were @ 270.00 and new mufflers are about a grand. Best check with Bryan.
I had crack mended for the past 2 annuals but I'll need to get new ones this year. I did get new sleeve heat shield shrouds this year. One of the guys on the forum told me about using hose clamps instead of screws in the corner where they crack due to vibration.
The cause is heat and vibration. I inspect mine every oil change to assure all is well a crack can go hole pretty fast and blow extreme heat right through the cowling. Nothing to play around with IMHO. Don't forget carbon Monoxide!
Bill
http://maulepilots.org/forums/viewtopic ... t=mufflers
I had crack mended for the past 2 annuals but I'll need to get new ones this year. I did get new sleeve heat shield shrouds this year. One of the guys on the forum told me about using hose clamps instead of screws in the corner where they crack due to vibration.
The cause is heat and vibration. I inspect mine every oil change to assure all is well a crack can go hole pretty fast and blow extreme heat right through the cowling. Nothing to play around with IMHO. Don't forget carbon Monoxide!
Bill
http://maulepilots.org/forums/viewtopic ... t=mufflers
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aero101
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another option other than new muffler is any certified exhaust repair shop can fix the can / shroud for about half cost of new muffler....
Jim
http://www.northstar-aero.com
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a64pilot
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Maule sold me the insides to my mufflers, they were easy to repair. Recommend you pull them off at every annual and look inside for the baffle Jeremy speaks of, also a sharp blow by your hand during every oil change will rattle the baffle if it gets broken off, that's how I found mine. The baffle is supported only on one end and will get broken up and completely blown out of the pipe in a surprisingly short time, then comes the hole in the side of the muffler and eventually the lower cowl.
It appears that the I/O 235's mufflers last longer than the O 235. I have a couple of theories on that.
I still want a complete new efficient single exhaust, may have to want for a while though.
It appears that the I/O 235's mufflers last longer than the O 235. I have a couple of theories on that.
I still want a complete new efficient single exhaust, may have to want for a while though.
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Gary JP4
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Outcome of TK Nashville's problem
Hello everyone.
I am the mechanic who made the repairs for TK Nashville to fix this problem. I am also a Maule pilot and instructor and have flown the aircraft off and on since he got it and some before that. I had done some minor work on the airplane before, but never had the opportunity to do an inspection.
I took the exhaust system off. While I was looking into it through commercial channels (Maule Air, Maule Flight, and aircraft exhaust shops) you folks simultaneously listed many of the same ideas for cause and repair in response to TK Nashville's query. You were all correct as to the cause. I don't usually do aircraft forums, but I was impressed with the value and depth of the responses here. I have a few thoughts and observations I wanted to add and let you all know the outcome for anyone having similar problems and perhaps finding this topic in a search.
Background: This aircraft is fairly new to TK and has less then 400 hours on it. Someone had done an annual just before he bought it. My first impression when seeing the damage to the muffler and cowl was that a valve had stuck. Subsequent inspection to the engine and exhaust indicated it was consistent with all that was stated here. The middle stack on the left side (carburetor heat side) is the one that blew through the muffler. On inspection the the other side, although intact on the outside, was also found to be missing the flame guard tube.
After seeing that the flame guard tube, and all remnants of it except the end inside the outlet to the tail pipe, were missing (on both sides), I talked to the folks at Maule Air and Maule Flight. Both had heard of cases turning all the way into a hole in the muffler, although they thought that was rare but said flame guard tubes are missing all the time. Bryan in parts said the average life of the tube was around 200 hours and they sell it separately as mentioned here. He said the average life of the rest of the muffler (and exhaust system I guess) is about 400 to 450 hours so our situation is about average. IMO that is ridiculously unacceptable.
A new system on a normally aspirated Cessna or Piper typically goes the TBO of the engine. Unfortunately exhaust parts often continue in service well beyond that, not being replaced at overhaul, or overhauls not being done, being replaced on demand (at failure). Consequently we get to see how long some parts really can last. It is often much longer then engine TBO.
IMO the problem is as follows (much of which has already been covered in this thread):
1) The flame guard is too thin (.035”). Yes, Maule sells them separately. However, they should be at least .049”. Heat, corrosion, erosion, and vibration cause the flame guard (tube) to break out in front of the rear outlet leaving only the last inch or so which is inside the muffler outlet tube. This is the tube on the back of the muffler that the tail pipe slides over and to which the flame guard is tack welded inside.
2) The flame tube is only supported at the rear. Supporting it at both ends (as mentioned here that someone modifies it that way on a field repair) must be a great idea because I had the same idea and recommended it to Aerospace Welding for their redesign. I don't know if they will listen.
3) The middle and rear stacks on each side come into the muffler at 90° . It might work better (last longer, and flow better) if they came in at an angle, turning with a bend toward the rear. This would cost something I am sure and may not be worth it.
4) Muffler material too light. They should consider making the whole assembly, mufflers and pipes, from heavier tubing. I am told there is also a problem with the rear of the muffler with the can cracking and tail pipe breaking off due to the weight and vibration of the tail pipe (even thought it is supported).
5) Inspections not being done. IMO Green Hornet is correct, it should be inspected at every oil change. You should remove the tail pipe and look up into the muffler with an inspection light, inspecting to see if the flame guard is intact, cracked, or missing.
6) Maule makes the mufflers themselves. They don't stock them, but make them to order in 3 days or so.
We elected not to go with new mufflers from Maule, but rather have them rebuilt by an aircraft exhaust shop hopping to improve on the situation and get a little better job and maybe service life. I have had good results with Aerospace Welding Minneapolis, Inc. in the past and chose them. I rarely if ever patch an exhaust part and when sending parts in for repair / rebuild it is not a repair like you might think. I can't say they don't use some part of the exhaust over again ,but when they do a rebuild it always looks like every part is new (a complete new assembly), all new welds with the tubes having the new material markings on them, etc. However, they don't have PMA approval on these particular mufflers so they need yours to work from (a core). You have to send yours in. Also, you should send everything in including the shrouds, short stacks, and tail pipes, even if they will not be replaced, so they can assure shrouds fits the muffler, pipes and stacks fit into the muffler, holes line up, etc. It is not cool to get new parts and find they don't fit together. Also, the aluminum heat shrouds are subject to misfit being critical because of the way they wrap around the flange on the muffler on both ends (a slight change in the flange angle or placement on the muffler and they wont fit). You might also talk them into using .049” instead of .035” material for the flame guard under the “same as original or better idea” of repair. They automatically put a doubler in the rear of the muffler to prevent cracking from the weight / vibration of the tail pipe. The price of a repair could be a lot lower, but the price of this rebuild is about the same as from Maule. Maybe a little more.
I hear they are working for Maule on a redesigned OEM application for this aircraft. If that goes through maybe the stuff coming from Maule will get better and last longer.
Other effects of a missing flame tube:
In addition to the things already mentioned like carbon monoxide poisoning and the need for inspection, I wanted to point out some things we noticed with this aircraft that might help you spot this condition or give reason to inspect and see if you are loosing the flame tubes as well as reasons to keep up with inspections.
We always thought this aircraft might have a very slight roughness at low RPM, and to some extent all over, but these big 6 cylinders do lope somewhat at low RPM. When pulling carburetor heat the engine would give some momentary roughness and stabilize. I didn't pay too much attention to this as it is normal in some applications. I even saw a statement in the POH of a Cherokee Six that said to pull the Carb Heat slowly to avoid roughness (and I think it even said something about possible momentary engine failure if pulled too fast). If slight power was carried on final approach we would sometimes (usually) get some backfire whenever the power was reduced to idle.
With the flame guards in place on both new mufflers the engine now feels and sounds noticeably smoother at all RPM's including idle, the carburetor heat no longer causes any momentary roughness if pulled abruptly, the fuel burn appears to be about 1 GPH lower, EGT's and CHT's match much more uniformly (CHT's are pretty much an even set of chips, and EGT's are almost even). It also sounds better. The engine seems to have a lower throatier sound now, although I thought it would be the other way around. The engine definitely likes the back pressure, or some other flow dynamics, created by the flame guards.
I am pretty sure, with these observations, that this is the difference in having the flame guards in place, that I was never flying it with a hole in the muffler, and that the hole only happened on the last flight where the metallic tap of an exhaust leak became apparent to TK. Obviously a hole in the muffler could have a more dramatic effect on these things then a missing flame guard tube.
The hole in the muffler did have a more significant effect on operation on the last flight. The EGT on the middle cylinder, the one aligned with the hole in the muffler, was higher then the rest and this was not the case before when we likely just had missing flame guards.
Note the aircraft has a JPI EDM 700, 6 probe EGT, CHT, with fuel flow computer.
Gary
I am the mechanic who made the repairs for TK Nashville to fix this problem. I am also a Maule pilot and instructor and have flown the aircraft off and on since he got it and some before that. I had done some minor work on the airplane before, but never had the opportunity to do an inspection.
I took the exhaust system off. While I was looking into it through commercial channels (Maule Air, Maule Flight, and aircraft exhaust shops) you folks simultaneously listed many of the same ideas for cause and repair in response to TK Nashville's query. You were all correct as to the cause. I don't usually do aircraft forums, but I was impressed with the value and depth of the responses here. I have a few thoughts and observations I wanted to add and let you all know the outcome for anyone having similar problems and perhaps finding this topic in a search.
Background: This aircraft is fairly new to TK and has less then 400 hours on it. Someone had done an annual just before he bought it. My first impression when seeing the damage to the muffler and cowl was that a valve had stuck. Subsequent inspection to the engine and exhaust indicated it was consistent with all that was stated here. The middle stack on the left side (carburetor heat side) is the one that blew through the muffler. On inspection the the other side, although intact on the outside, was also found to be missing the flame guard tube.
After seeing that the flame guard tube, and all remnants of it except the end inside the outlet to the tail pipe, were missing (on both sides), I talked to the folks at Maule Air and Maule Flight. Both had heard of cases turning all the way into a hole in the muffler, although they thought that was rare but said flame guard tubes are missing all the time. Bryan in parts said the average life of the tube was around 200 hours and they sell it separately as mentioned here. He said the average life of the rest of the muffler (and exhaust system I guess) is about 400 to 450 hours so our situation is about average. IMO that is ridiculously unacceptable.
A new system on a normally aspirated Cessna or Piper typically goes the TBO of the engine. Unfortunately exhaust parts often continue in service well beyond that, not being replaced at overhaul, or overhauls not being done, being replaced on demand (at failure). Consequently we get to see how long some parts really can last. It is often much longer then engine TBO.
IMO the problem is as follows (much of which has already been covered in this thread):
1) The flame guard is too thin (.035”). Yes, Maule sells them separately. However, they should be at least .049”. Heat, corrosion, erosion, and vibration cause the flame guard (tube) to break out in front of the rear outlet leaving only the last inch or so which is inside the muffler outlet tube. This is the tube on the back of the muffler that the tail pipe slides over and to which the flame guard is tack welded inside.
2) The flame tube is only supported at the rear. Supporting it at both ends (as mentioned here that someone modifies it that way on a field repair) must be a great idea because I had the same idea and recommended it to Aerospace Welding for their redesign. I don't know if they will listen.
3) The middle and rear stacks on each side come into the muffler at 90° . It might work better (last longer, and flow better) if they came in at an angle, turning with a bend toward the rear. This would cost something I am sure and may not be worth it.
4) Muffler material too light. They should consider making the whole assembly, mufflers and pipes, from heavier tubing. I am told there is also a problem with the rear of the muffler with the can cracking and tail pipe breaking off due to the weight and vibration of the tail pipe (even thought it is supported).
5) Inspections not being done. IMO Green Hornet is correct, it should be inspected at every oil change. You should remove the tail pipe and look up into the muffler with an inspection light, inspecting to see if the flame guard is intact, cracked, or missing.
6) Maule makes the mufflers themselves. They don't stock them, but make them to order in 3 days or so.
We elected not to go with new mufflers from Maule, but rather have them rebuilt by an aircraft exhaust shop hopping to improve on the situation and get a little better job and maybe service life. I have had good results with Aerospace Welding Minneapolis, Inc. in the past and chose them. I rarely if ever patch an exhaust part and when sending parts in for repair / rebuild it is not a repair like you might think. I can't say they don't use some part of the exhaust over again ,but when they do a rebuild it always looks like every part is new (a complete new assembly), all new welds with the tubes having the new material markings on them, etc. However, they don't have PMA approval on these particular mufflers so they need yours to work from (a core). You have to send yours in. Also, you should send everything in including the shrouds, short stacks, and tail pipes, even if they will not be replaced, so they can assure shrouds fits the muffler, pipes and stacks fit into the muffler, holes line up, etc. It is not cool to get new parts and find they don't fit together. Also, the aluminum heat shrouds are subject to misfit being critical because of the way they wrap around the flange on the muffler on both ends (a slight change in the flange angle or placement on the muffler and they wont fit). You might also talk them into using .049” instead of .035” material for the flame guard under the “same as original or better idea” of repair. They automatically put a doubler in the rear of the muffler to prevent cracking from the weight / vibration of the tail pipe. The price of a repair could be a lot lower, but the price of this rebuild is about the same as from Maule. Maybe a little more.
I hear they are working for Maule on a redesigned OEM application for this aircraft. If that goes through maybe the stuff coming from Maule will get better and last longer.
Other effects of a missing flame tube:
In addition to the things already mentioned like carbon monoxide poisoning and the need for inspection, I wanted to point out some things we noticed with this aircraft that might help you spot this condition or give reason to inspect and see if you are loosing the flame tubes as well as reasons to keep up with inspections.
We always thought this aircraft might have a very slight roughness at low RPM, and to some extent all over, but these big 6 cylinders do lope somewhat at low RPM. When pulling carburetor heat the engine would give some momentary roughness and stabilize. I didn't pay too much attention to this as it is normal in some applications. I even saw a statement in the POH of a Cherokee Six that said to pull the Carb Heat slowly to avoid roughness (and I think it even said something about possible momentary engine failure if pulled too fast). If slight power was carried on final approach we would sometimes (usually) get some backfire whenever the power was reduced to idle.
With the flame guards in place on both new mufflers the engine now feels and sounds noticeably smoother at all RPM's including idle, the carburetor heat no longer causes any momentary roughness if pulled abruptly, the fuel burn appears to be about 1 GPH lower, EGT's and CHT's match much more uniformly (CHT's are pretty much an even set of chips, and EGT's are almost even). It also sounds better. The engine seems to have a lower throatier sound now, although I thought it would be the other way around. The engine definitely likes the back pressure, or some other flow dynamics, created by the flame guards.
I am pretty sure, with these observations, that this is the difference in having the flame guards in place, that I was never flying it with a hole in the muffler, and that the hole only happened on the last flight where the metallic tap of an exhaust leak became apparent to TK. Obviously a hole in the muffler could have a more dramatic effect on these things then a missing flame guard tube.
The hole in the muffler did have a more significant effect on operation on the last flight. The EGT on the middle cylinder, the one aligned with the hole in the muffler, was higher then the rest and this was not the case before when we likely just had missing flame guards.
Note the aircraft has a JPI EDM 700, 6 probe EGT, CHT, with fuel flow computer.
Gary
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Green Hornet
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Re: Outcome of TK Nashville's problem
Hi Gary,
Thanks for the great follow up report on the muffler system. Like I said my mufflers have been patched to the point that the muffler shop said it is not possible to patch again.
Based on the following:
Thanks Again
Bill
Thanks for the great follow up report on the muffler system. Like I said my mufflers have been patched to the point that the muffler shop said it is not possible to patch again.
Based on the following:
This sounds like the way to go did you get TK's " rebulit muffler back yet and did you get a price? I will not have to consider this until February but I would like the contact name and phone number.Gary JP4 wrote:
We elected not to go with new mufflers from Maule, but rather have them rebuilt by an aircraft exhaust shop hopping to improve on the situation and get a little better job and maybe service life. I have had good results with Aerospace Welding Minneapolis, Inc. in the past and chose them. I rarely if ever patch an exhaust part and when sending parts in for repair / rebuild it is not a repair like you might think. I can't say they don't use some part of the exhaust over again ,but when they do a rebuild it always looks like every part is new (a complete new assembly), all new welds with the tubes having the new material markings on them, etc. However, they don't have PMA approval on these particular mufflers so they need yours to work from (a core). You have to send yours in. Also, you should send everything in including the shrouds, short stacks, and tail pipes, even if they will not be replaced, so they can assure shrouds fits the muffler, pipes and stacks fit into the muffler, holes line up, etc. It is not cool to get new parts and find they don't fit together. Also, the aluminum heat shrouds are subject to misfit being critical because of the way they wrap around the flange on the muffler on both ends (a slight change in the flange angle or placement on the muffler and they wont fit). You might also talk them into using .049” instead of .035” material for the flame guard under the “same as original or better idea” of repair. They automatically put a doubler in the rear of the muffler to prevent cracking from the weight / vibration of the tail pipe. The price of a repair could be a lot lower, but the price of this rebuild is about the same as from Maule. Maybe a little more.
Thanks Again
Bill
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Gary JP4
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We did get them back and all the comments on how it runs better are based on the new mufflers.
I haven't billed him yet and don't remember how much each part was as we had some more of the system parts (pipes) repaired too. I don't have the paper work in front of me. I will get back to you on the muffler price but I remember it was about the same or a little higher then from Maule. They may have up charged me for the heavier material too.
If they had a core in stock or had already made one (I mean rebuilt one) you could just buy it, they would bill you a core charge, and you could send yours back when you got the new one for a core refund. Although it is better to send yours in for fitting like I mentioned.
They didn't have any in stock when we started this so I sent them everything.
Gary
I haven't billed him yet and don't remember how much each part was as we had some more of the system parts (pipes) repaired too. I don't have the paper work in front of me. I will get back to you on the muffler price but I remember it was about the same or a little higher then from Maule. They may have up charged me for the heavier material too.
If they had a core in stock or had already made one (I mean rebuilt one) you could just buy it, they would bill you a core charge, and you could send yours back when you got the new one for a core refund. Although it is better to send yours in for fitting like I mentioned.
They didn't have any in stock when we started this so I sent them everything.
Gary
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Green Hornet
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Gary JP4
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UP-M5
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shipping might be slightly more, but these guys know how to rebuild a maule muffler: http://www.fadodge.com/
i have used AWI and Atlee Dodge with good results on both accounts. also similar prices ~ $500 each muffler. i now also keep an overhauled pair of mufflers in the hangar. summer is too short to be waiting for parts
i have used AWI and Atlee Dodge with good results on both accounts. also similar prices ~ $500 each muffler. i now also keep an overhauled pair of mufflers in the hangar. summer is too short to be waiting for parts
M5-235
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Hottshot
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As long as AWI pulls 25# outa their system I think it will be great, but as it sits adding another 30 lbs to the front of the Maule is not a good idea for me. Quality was good but to blasted heavy. Now the 180hp Maule could use a pound or two up there but not much.
Wup Winn
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Joseph Or, 97846
info@backcountryconnection.com
wup@maulesales.com
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541-263-2968
Joseph Or, 97846
info@backcountryconnection.com
wup@maulesales.com
www.backcountryconnection.com
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Green Hornet
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So it is a trade off quality versus weight and speed and climb.Hottshot wrote:As long as AWI pulls 25# outa their system I think it will be great, but as it sits adding another 30 lbs to the front of the Maule is not a good idea for me. Quality was good but to blasted heavy. Now the 180hp Maule could use a pound or two up there but not much.
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MauleWacko
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I've got the right hand side exhaust system removed from my O-360 (4 cyl) because I had a crack where the front inlet pipe is welded onto the muffler. I'm getting the crack repaired but the muffler otherwise appears to be in good shape. Pardon my ignorance but this reference to flame guards has me worried because I don't know what they are. When I look up the exhaust port to which the tail pipe is connected what I see resembles a tube made of expanded metal grating running all the way through from back to front. There doesn't appear to be anything else up there. Is this the flame guard or am I missing something?
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