Greg Ellis Posted February 9, 2019 Report Share Posted February 9, 2019 Flew to Columbia Missouri from Fort Worth Texas yesterday. When I was about 5 minutes out I started hearing a very loud, rhythmic noise coming from the airplane. It would change in frequency with change in power setting and go completely silent when idle. It was loud enough to hear it through noise cancelling headsets. Checking all instruments, etc...everything looked fine except for one thing. On the EDM 900 the #4 cylinder was running colder than the other 3 and the EGT was almost non existent. It was there but so far less than the other cylinders. The plane was still flying just fine. Oil temp and pressure was fine. So I landed and taxied to parking. Fortunately there is a mechanic shop right there. The EDM 900 pointed to the #4 cylinder and this is what we found: The rhythmic noise I heard was the cylinder venting into the engine compartment instead of out the exhaust. And that seems to be why I heard the frequency changes with change in power settings. Suffice to say, I am back in Fort Worth. The plane is still in Missouri. 3 Quote Link to comment Share on other sites More sharing options...
211º Posted February 9, 2019 Report Share Posted February 9, 2019 This is one thing that I like about the EDM and also about Mooneyspace - learning what the EDM is showing and then seeing real world what those measurements mean. Thank you very much for posting. 2 Quote Link to comment Share on other sites More sharing options...
ArtVandelay Posted February 9, 2019 Report Share Posted February 9, 2019 How old or how long since your exhaust was overhauled?Tom Quote Link to comment Share on other sites More sharing options...
Greg Ellis Posted February 9, 2019 Author Report Share Posted February 9, 2019 11 minutes ago, ArtVandelay said: How old or how long since your exhaust was overhauled? Tom Honestly I am not sure and I have not checked the logs. It has not been done since I have owned the airplane and that has been 12 years. It has been repaired in one other spot on the #3 cylinder a few years ago. Quote Link to comment Share on other sites More sharing options...
DonMuncy Posted February 9, 2019 Report Share Posted February 9, 2019 Tough break Greg. Hope you get going quickly. Quote Link to comment Share on other sites More sharing options...
Marauder Posted February 9, 2019 Report Share Posted February 9, 2019 Greg - I had a similar experience involving my exhaust. In my case, I was flying behind one of the original Insight GEMs. I noticed a fluctuating EGT on one cylinder and then suddenly the EGT went away and I was riding a Harley. One of the studs had been cranked down too tight and the stud cracked and eventually broke. What I saw was the second stud’s nut loosing up and eventually falling off allowing the entire exhaust pipe to fall into the cowling. The CHT temp still displayed (inverted in color). The thing I remember the most was the loud popping as I pulled power to glide to the airport. Sent from my iPhone using Tapatalk Pro 1 Quote Link to comment Share on other sites More sharing options...
carusoam Posted February 10, 2019 Report Share Posted February 10, 2019 Great pirep with pic, Greg! Wonder If There is a procedure for mounting that exhaust system to relieve torque, while tightening things up... or an annual procedure... Differential expansion of various metals and temperatures puts a lot of strain on the parts. Somebody posted a similar pic of a crack on an IO550 recently... three cylinders and the exhaust pipe have a lot of motion... expansion and vibration... PP thoughts only, not a mechanic. Best regards, -a- Quote Link to comment Share on other sites More sharing options...
Guest Posted February 10, 2019 Report Share Posted February 10, 2019 7 hours ago, carusoam said: Great pirep with pic, Greg! Wonder If There is a procedure for mounting that exhaust system to relieve torque, while tightening things up... or an annual procedure... Differential expansion of various metals and temperatures puts a lot of strain on the parts. Somebody posted a similar pic of a crack on an IO550 recently... three cylinders and the exhaust pipe have a lot of motion... expansion and vibration... PP thoughts only, not a mechanic. Best regards, -a- Anthony, Lycoming generally use a plain steel nut (STD 1410)and lock washer, Diamond is the only one I know of who use a steel lock nut on a Lycoming. Continental 360’s use a brass nut and the 520-550’s use a lock nut. Clarence Quote Link to comment Share on other sites More sharing options...
Pete M Posted February 10, 2019 Report Share Posted February 10, 2019 I recall having to send my exhaust system out for overhaul in 2005 to someplace in MN I think. They had an ad in trade a plane or some such thing. I was suprised when I got back what appeared to be a whole new system. Total cost was $1400. I imagine it would be quite a bit more today. Time for a powerflow? I think my origunal lasted 4000 hours. Is the exhaust an item that should be replaced at OH? Quote Link to comment Share on other sites More sharing options...
rbridges Posted February 10, 2019 Report Share Posted February 10, 2019 Just wondering. Do you have a CO monitor, and did it register anything? Also, does CHT go down because of lower cylinder back pressure? 1 Quote Link to comment Share on other sites More sharing options...
DXB Posted February 10, 2019 Report Share Posted February 10, 2019 Yikes - thanks for posting and sharing the experience. Sounds like a technical error installing the exhaust might have contributed. I probably should spend more time than I do staring at the exhaust when the cowl is opened up. Also my exhaust just passed its 20th birthday and about 2000 hrs (the engine has much less). Is there a time point where it’s just prudent to replace it? Quote Link to comment Share on other sites More sharing options...
Greg Ellis Posted February 10, 2019 Author Report Share Posted February 10, 2019 1 hour ago, rbridges said: Just wondering. Do you have a CO monitor, and did it register anything? Also, does CHT go down because of lower cylinder back pressure? I do have a CO monitor on board. It is a very sensitive monitor and not just one of the cards that changes color. It never showed anything nor did the alarm go off. I got an occasional smell of exhaust in the cabin but no where near what you would expect. Just an occasional odor. As far as the CHT levels, I am not sure. But they were much colder than the other 3 cylinders. The big difference was of course the EGT on this cylinder being very cold compared to the others. I was not able to download the data. I was scrambling to speak to the mechanics, get to my meeting and then get an airline flight after my meeting. I caught the last flight out of Columbia to DFW for the day. I really did not have the time to even think about things let alone get the data. I will download the flight when I return. 1 Quote Link to comment Share on other sites More sharing options...
rbridges Posted February 10, 2019 Report Share Posted February 10, 2019 17 minutes ago, Greg Ellis said: I do have a CO monitor on board. It is a very sensitive monitor and not just one of the cards that changes color. It never showed anything nor did the alarm go off. I got an occasional smell of exhaust in the cabin but no where near what you would expect. Just an occasional odor. As far as the CHT levels, I am not sure. But they were much colder than the other 3 cylinders. The big difference was of course the EGT on this cylinder being very cold compared to the others. I was not able to download the data. I was scrambling to speak to the mechanics, get to my meeting and then get an airline flight after my meeting. I caught the last flight out of Columbia to DFW for the day. I really did not have the time to even think about things let alone get the data. I will download the flight when I return. Thanks. The CHT question was actually a general question for the forum, and I should have asked separately. Thanks for the feedback on the monitor. Quote Link to comment Share on other sites More sharing options...
Greg Ellis Posted February 25, 2019 Author Report Share Posted February 25, 2019 I just got the plane back yesterday. Flew it from Columbia MO back to Fort Worth Texas. Plane flew very well. I just wanted to give a Pirep to a great shop at the Columbia Regional Airport (KCOU) if anyone ever needs help. Columbia Avionics were awesome. They fit me right into their extremely busy schedule, had me diagnosed and parts ordered the very day I had the problem and got me fixed in a very timely manner. They even made room in their already full hangar to keep me out of the unbearably cold weather up there. I cannot say enough about them and how great they treated me. 1 Quote Link to comment Share on other sites More sharing options...
Shadrach Posted February 25, 2019 Report Share Posted February 25, 2019 On 2/10/2019 at 9:18 AM, rbridges said: Just wondering. Do you have a CO monitor, and did it register anything? Also, does CHT go down because of lower cylinder back pressure? If the cylinder being discussed was running at peak or leaner, little to no CO was being produced as a result of combustion. In that situation one would need a NOx monitor to sense exhaust entering the cockpit. 1 Quote Link to comment Share on other sites More sharing options...
Greg Ellis Posted February 25, 2019 Author Report Share Posted February 25, 2019 36 minutes ago, Shadrach said: If the cylinder being discussed was running at peak or leaner, little to no CO was being produced as a result of combustion. In that situation one would need a NOx monitor to sense exhaust entering the cockpit. There was a slight smell of just the exhaust but my CO monitor did not alarm nor did it show any change at all. It was not being run LOP because my O-360 with the carburetor won't even come close to LOP. Quote Link to comment Share on other sites More sharing options...
Yetti Posted February 25, 2019 Report Share Posted February 25, 2019 I believe this might be a case for mouse milk on all the slip joints each time the cowl is off. Quote Link to comment Share on other sites More sharing options...
Guest Posted February 25, 2019 Report Share Posted February 25, 2019 15 minutes ago, Yetti said: I believe this might be a case for mouse milk on all the slip joints each time the cowl is off. And a pressure check with an old shop vacuum during Annual. Clarence Quote Link to comment Share on other sites More sharing options...
Greg Ellis Posted February 25, 2019 Author Report Share Posted February 25, 2019 57 minutes ago, Yetti said: I believe this might be a case for mouse milk on all the slip joints each time the cowl is off. That is a good idea although the mechanic said that nothing was fused and when he took this part of the exhaust off it came apart pretty easy at the slip joints. But it is a good idea non the less. Thanks. Quote Link to comment Share on other sites More sharing options...
N201MKTurbo Posted February 25, 2019 Report Share Posted February 25, 2019 I have found when an exhaust cracks like that and forms a gap, it has a lot of built in stress and has gotten to the low stress state. That can happen if it wasn't built right in the first place, wasn't assembled correctly or slip joints seized. It is important when assembling the exhaust system that the whole system is assembled kind of loose and then sequentially tightening the nuts. If any of the nuts are pulling the system into place, cracks like yours may happen. Sometimes it is necessary to shake it or whack it with a soft hammer to get it so it all lines up properly. You should make sure all your slip joints will slide by hand when lubricated with anti seize. It sometimes takes a lot of wire brushing and sanding to get all the old deposits and corrosion off the inside and outside of the slip joints. 1 Quote Link to comment Share on other sites More sharing options...
Guest Posted February 25, 2019 Report Share Posted February 25, 2019 34 minutes ago, N201MKTurbo said: I have found when an exhaust cracks like that and forms a gap, it has a lot of built in stress and has gotten to the low stress state. That can happen if it wasn't built right in the first place, wasn't assembled correctly or slip joints seized. It is important when assembling the exhaust system that the whole system is assembled kind of loose and then sequentially tightening the nuts. If any of the nuts are pulling the system into place, cracks like yours may happen. Sometimes it is necessary to shake it or whack it with a soft hammer to get it so it all lines up properly. You should make sure all your slip joints will slide by hand when lubricated with anti seize. It sometimes takes a lot of wire brushing and sanding to get all the old deposits and corrosion off the inside and outside of the slip joints. It may also be a case of the exhaust port on that cylinder being re surfaced at some point in its life making it shorter than the adjacent one. Clarence Quote Link to comment Share on other sites More sharing options...
67 m20F chump Posted February 25, 2019 Report Share Posted February 25, 2019 I have had good luck with Dawley Aviation for this kind of repair. Reasonable prices too. Quote Link to comment Share on other sites More sharing options...
Shadrach Posted February 25, 2019 Report Share Posted February 25, 2019 2 hours ago, N201MKTurbo said: I have found when an exhaust cracks like that and forms a gap, it has a lot of built in stress and has gotten to the low stress state. That can happen if it wasn't built right in the first place, wasn't assembled correctly or slip joints seized. It is important when assembling the exhaust system that the whole system is assembled kind of loose and then sequentially tightening the nuts. If any of the nuts are pulling the system into place, cracks like yours may happen. Sometimes it is necessary to shake it or whack it with a soft hammer to get it so it all lines up properly. You should make sure all your slip joints will slide by hand when lubricated with anti seize. It sometimes takes a lot of wire brushing and sanding to get all the old deposits and corrosion off the inside and outside of the slip joints. I agree. That pipe is now offset by at least 1/8” from its mounted position. There is no question that this is the position it was seeking. That’s a stress crack. No evidence of corrosion or significant thinning that I can see in the image. It looks like it pulled away at the flange weld. Quote Link to comment Share on other sites More sharing options...
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