Rjfanjet Posted May 9, 2021 Report Share Posted May 9, 2021 So I have an EGT probe on each exhaust stack. Rotating through them, number 1 was significantly different than the others, much lower than the others. In January I replaced all spark plugs and added a Power Flow exhaust. I mentioned this to my mechanic last week when we upgraded the ELT. We checked the cylinder and found the top spark plug not even finger tight. I've never seen this before. Any ideas as to what would cause the plug to vibrate loose? Thanks Quote Link to comment Share on other sites More sharing options...
A64Pilot Posted May 9, 2021 Report Share Posted May 9, 2021 Wasn’t properly torqued 3 Quote Link to comment Share on other sites More sharing options...
MB65E Posted May 9, 2021 Report Share Posted May 9, 2021 Ummm, not using a new gasket or torque wrench. Only plug I have ever seen come loose was the one in my uncles Briggs & Stratton go cart. That’s because the threads were shot. It would shoot spark plugs. 150ft! -Matt 1 Quote Link to comment Share on other sites More sharing options...
PT20J Posted May 9, 2021 Report Share Posted May 9, 2021 And don’t forget the gasket. Someone did that on a couple of plugs on the museum DC-3 last year. It leaves about 2-3 threads protruding into the cylinder which get carboned up, and it was a real PITA removing them. Skip Quote Link to comment Share on other sites More sharing options...
cliffy Posted May 9, 2021 Report Share Posted May 9, 2021 15 hours ago, PT20J said: And don’t forget the gasket. Someone did that on a couple of plugs on the museum DC-3 last year. It leaves about 2-3 threads protruding into the cylinder which get carboned up, and it was a real PITA removing them. Skip Or they miss one sticking on the plug and have two on the plug putting the tip too far up in the cylinder head. Have seen that one also. I buy copper spark plug gaskets by the 100 and any time I remove a plug a new gasket goes on. Cheap insurance. Also remember that Continental and Lycoming have different torque values for their plugs One size doesn't fit all. 2 Quote Link to comment Share on other sites More sharing options...
cliffy Posted May 9, 2021 Report Share Posted May 9, 2021 No one has mentioned WHY the gaskets need to be replaced every time they come off Copper gaskets turn "hard" after use on the engine and won't "crush" as they should to seal the spark plug hole when retightened New gaskets are soft copper and crush correctly upon tightening for a proper seal. One can also "anneal" the old gaskets to a soft condition by heating them cherry red a dropping them in water to quickly cool and anneal them. Copper and aluminum soften by quenching BUT steel hardens by quenching Something to remember. 3 Quote Link to comment Share on other sites More sharing options...
carusoam Posted May 9, 2021 Report Share Posted May 9, 2021 Go MS! -a- Quote Link to comment Share on other sites More sharing options...
RLCarter Posted May 9, 2021 Report Share Posted May 9, 2021 (edited) No one has asked, but is it possible that the plug was never tightened to begin with? Edited May 9, 2021 by RLCarter Quote Link to comment Share on other sites More sharing options...
Yetti Posted May 10, 2021 Report Share Posted May 10, 2021 (edited) There is a well known Mooney MSC in East Texas. There was a Mooney came out of annual that went from there to a Mooney Safety clinic. There were engine troubles. All the spark plugs were only finger tight. Edited May 10, 2021 by Yetti Quote Link to comment Share on other sites More sharing options...
Rjfanjet Posted May 10, 2021 Author Report Share Posted May 10, 2021 Thanks for the replies. I checked all other plugs, they were torqued to spec. Quote Link to comment Share on other sites More sharing options...
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