sleepingsquirrel Posted December 7, 2014 Report Share Posted December 7, 2014 Hey! I flew the Mooney yesterday and something happened at 6000 feet. I knew something was wrong but was seeing nothing I could really put my finger on. In flight mag check, ok. Carb heat seemed to help but then not so much. Mixture more rich helped but then not so much. Increasing the RPM helped smooth out the vibration. Low Rpm to descend made me think possibly that I had lost a prop tip. I flew the airplane to home port and landed and exited the runway with a badly vibrating engine. Run up at the tie down made the vibration go away but when RPM reduced vibration came back. I tied the thing down thinking that it was a probable intake/exhaust valve sticking . This morning I went back with the intent to run it and then find the cold cylinder. I found #4 was cold. Then I found this. Surprise! induction leak. I'll have my mechanic put this back in order. 1 Quote Link to comment Share on other sites More sharing options...
carusoam Posted December 7, 2014 Report Share Posted December 7, 2014 That's some pretty quick problem solving technique! Anyone else ever seen that happen before? Best regards, -a- Quote Link to comment Share on other sites More sharing options...
BigTex Posted December 7, 2014 Report Share Posted December 7, 2014 Yep... Had then same thing happen when my MP line came disconnected from my #3 cylinder. When I was taxiing in that cylinder went cold and felt like the engine was about to come apart. Quote Link to comment Share on other sites More sharing options...
Danb Posted December 7, 2014 Report Share Posted December 7, 2014 For those of us who are mechanically challenged what am I looking at..The hole I assume is so what is the effect Thanx. Dan Quote Link to comment Share on other sites More sharing options...
carusoam Posted December 8, 2014 Report Share Posted December 8, 2014 That is where a vacuum sensor can be placed for measuring MP... It had a plug in the hole because the MP is probably on another cylinder. When the plug comes out excess air is allowed to rush in and make an unusable lean mixture for that one cylinder and can effect the other cylinders way up stream... At WOT, the added air won't be as much of a challenge as at low throttle position. Running really rough would be expected at WOT. Getting it started with a 'cracked' throttle setting was not going to happen. Is that understandable? (I'm trying, but I might be in over my head) Best regards, -a- Quote Link to comment Share on other sites More sharing options...
sleepingsquirrel Posted December 8, 2014 Author Report Share Posted December 8, 2014 For those of us who are mechanically challenged what am I looking at..The hole I assume is so what is the effect Thanx. Dan Seems each cylinder has two. One on top one on bottom into the area above the intake valve. I think they are for fuel injection nozzle / primer nozzle or Manifold pressure. Quote Link to comment Share on other sites More sharing options...
carusoam Posted December 8, 2014 Report Share Posted December 8, 2014 There is a good Lock-Tite product that will keep that from happening again. Red for never coming out again and Blue for taking some effort to get it out again... It's nice to see the parts catching tray still works! My C used to deposit fasteners from the dog house there... Best regards, -a- Check with your mechanic. I'm only a PP... Quote Link to comment Share on other sites More sharing options...
sleepingsquirrel Posted December 8, 2014 Author Report Share Posted December 8, 2014 My favorite sealant/ thread locker. I'll be checking them all. Quote Link to comment Share on other sites More sharing options...
RobertGary1 Posted December 8, 2014 Report Share Posted December 8, 2014 You're going to pay a mechanic to screw in a plug? -Robert Quote Link to comment Share on other sites More sharing options...
carusoam Posted December 8, 2014 Report Share Posted December 8, 2014 Robert, Great question! I prefer my certified mechanic to handle all things that effect the proper operation of my power plant... Questions I consider for this type of work.... Is that on the list of things I am allowed to do? If I select an improper thread locker, does this happen again? Is there a proper torque for that? Hot or cold? Would I have a torque wrench? How much will my mechanic charge? Somebody might recomend something like a hangar fairy or a pixie that may handle it... Probably a question that you may have to answer for yourself... Keep in mind, if I were to torque that plug in my cylinder, I would be paying my mechanic to replace the cracked cylinder head. I've gotten to know myself over a long period of time. My mechanic loves to help me out on simple things... Yes, I have broken expensive things with the guidance of my mechanic. Time for me to do this: approximately 5 hours. Time for my mechanic: approximately 5 minutes (I get to uncowl and recowl) I'll get my five minutes worth by asking all these questions, while he is torquing that plug. Best regards, -a- 1 Quote Link to comment Share on other sites More sharing options...
sleepingsquirrel Posted December 8, 2014 Author Report Share Posted December 8, 2014 You're going to pay a mechanic to screw in a plug? -Robert Sadly, does this fall under preventive maintenance? If it was just loose, could a Pilot legally tighten it? Technically this is not beyond even the most mechanically inept pilot. Certainly not as difficult as replacing a spark plug (allowed). If you will make note of the winking emoticon you will have an answer to your question. I've been around airplanes all my life. Owning an aircraft is like owning a Mercedes, affordable, if you can work on it. I didn't need a mechanic to tell me how to troubleshoot this issue. I doubt I need one for finding this repaired. It screwed itself out I'll just wait until it screws itself back in. thermal coefficient of expansion for aluminium is 12(10-6 in/(in oF))*) thermal coefficient of expansion for steel is 6 (10-6 in/(in oF))*) The aluminium hole will always get bigger than the steel can expand to fill the hole. This is why it got loose with no locker/sealant in place. 1 Quote Link to comment Share on other sites More sharing options...
sleepingsquirrel Posted December 8, 2014 Author Report Share Posted December 8, 2014 At WOT, the added air won't be as much of a challenge as at low throttle position. Running really rough would be expected at WOT. Getting it started with a 'cracked' throttle setting was not going to happen. -a- Actually it was less noticeable at higher power. It started this morning with the plug out. the reason I know it came out during flight is I was climbing @ 1100 FPM to 6000 feet. Can't do that on three cylinders. Quote Link to comment Share on other sites More sharing options...
carusoam Posted December 8, 2014 Report Share Posted December 8, 2014 Steel plug in an aluminum hole... Any noticeable electrolysis issues from the different metals being in contact with each other. I would expect a certain amount of added electrical activity with the spark plug being nearby? That escaped my thought process... Best regards, -a- Quote Link to comment Share on other sites More sharing options...
sleepingsquirrel Posted December 8, 2014 Author Report Share Posted December 8, 2014 All the threads were clean, absolutely clean ,no corrosion. There was a slight sign of rust (iron oxide) in the hex drive of the plug. If there was corrosion I doubt it would have come out at all. These cylinder assemblies have many steel /aluminum contact surfaces with no corrosion issues. This plug is listed in the parts guide as 1/8 x27 x pipe thread. There are different tapers for pipe threads but pipe thread tends to wedge itself into the female thread for sealing and locking.. Quote Link to comment Share on other sites More sharing options...
RobertGary1 Posted December 8, 2014 Report Share Posted December 8, 2014 Questions I consider for this type of work.... Is that on the list of things I am allowed to do? To clarify, the FAA places no restrictions on who can do work. The limitation is on who can sign the work off and return the aircraft to service. If you have an A&P who is used to receiving regular cash from you he should not object to walking over, looking at a screw you installed, and determine it was installed correctly and signing it off. I would be surprised if you were charged for this 5 minutes of work if you otherwise use him for work. He can even log it as "MP pressure plug cylinder #3 installed by owner...". -Robert 1 Quote Link to comment Share on other sites More sharing options...
Yetti Posted December 8, 2014 Report Share Posted December 8, 2014 The real question is Who installed this one such that it was allowed to vibrate loose and are the other ones loose? Now your mechanics time is up to an hour to remove and thread lock all the other ones. Quote Link to comment Share on other sites More sharing options...
sleepingsquirrel Posted December 8, 2014 Author Report Share Posted December 8, 2014 These cylinders were put on about 250 hours ago during OH. The torque spec for 1/8 steel pipe plug into aluminum is 40 inch pounds or 3.3333333333333 foot pounds. Quote Link to comment Share on other sites More sharing options...
Yetti Posted December 8, 2014 Report Share Posted December 8, 2014 All the cool kids use newtons... or at least my BMW motorcycle does Quote Link to comment Share on other sites More sharing options...
RobertGary1 Posted December 8, 2014 Report Share Posted December 8, 2014 These cylinders were put on about 250 hours ago during OH. The torque spec for 1/8 steel pipe plug into aluminum is 40 inch pounds or 3.3333333333333 foot pounds. The cylinder should have been shipped with the plug installed. Was this a new cylinder? -Robert Quote Link to comment Share on other sites More sharing options...
carusoam Posted December 8, 2014 Report Share Posted December 8, 2014 Confirming I don't have a torque wrench that light... -a- Quote Link to comment Share on other sites More sharing options...
N201MKTurbo Posted December 8, 2014 Report Share Posted December 8, 2014 I know you are all trying to be proper, but it is a pipe thread plug, screw it back in. 40 In/lbs is good and snug with a screwdriver handle, or as tight as you can get it with the short end of an Allen wrench without making your fingers hurt. If you want to be perfectly proper, go buy a good torque screwdriver, send it out to a certified calibration facility so it has a current calibration sticker, and then screw it in to the correct torque. I think 90% of the mechanics out there would just screw it back in unless the FAA inspector is in the building. 1 Quote Link to comment Share on other sites More sharing options...
sleepingsquirrel Posted December 8, 2014 Author Report Share Posted December 8, 2014 The cylinder should have been shipped with the plug installed. Was this a new cylinder? -Robert I'll have to check the logs . I doubt they were new but from a rebuild shop. Quote Link to comment Share on other sites More sharing options...
sleepingsquirrel Posted December 8, 2014 Author Report Share Posted December 8, 2014 I know you are all trying to be proper, but it is a pipe thread plug, screw it back in. 40 In/lbs is good and snug with a screwdriver handle, or as tight as you can get it with the short end of an Allen wrench without making your fingers hurt. If you want to be perfectly proper, go buy a good torque screwdriver, send it out to a certified calibration facility so it has a current calibration sticker, and then screw it in to the correct torque. I think 90% of the mechanics out there would just screw it back in unless the FAA inspector is in the building. I fully agree , as I said on the Purple Board, tight enough but not too tight. It is not rocket science. 1 Quote Link to comment Share on other sites More sharing options...
scottfromiowa Posted December 8, 2014 Report Share Posted December 8, 2014 Glad you didn't have to "work" your foot-note. All good. Quote Link to comment Share on other sites More sharing options...
sleepingsquirrel Posted December 9, 2014 Author Report Share Posted December 9, 2014 That's some pretty quick problem solving technique! Anyone else ever seen that happen before? Best regards, -a- One other person on the Purple Board had it happen on an O-320 in a Pacer. Today I checked the #1;#3 cylinders and found one not tight (needed attention) out of three ports. 1 Quote Link to comment Share on other sites More sharing options...
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