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Hello! I own a 1976 Mooney M20F named Loreto. This is my first post on a Mooneyspace forum, so please forgive me if I do it wrong. ◡̈ On 2/17 I heard a slow, deep, repetitive grinding noise coming from my plane after landing that I had never heard before. It was very loud and coming from within the airframe somewhere below and slightly behind the front left seat. The green GEAR DOWN indicator light on the panel was flickering a little. When I turned the master switch off, it stopped. When I turned the master switch back on, the sound and flickering returned. If I sat very still, I could feel my seat vibrating a little in sync with the sound. The DPE sitting next to me in the plane when this occurred suggested it may be an issue with my electric landing gear motor so I took the plane to the only maintenance facility on the airfield, Foothill Aircraft at Cable Airport. The mechanics at Foothill are hypothesizing... "a spring is snapping back and hitting a switch to tell the motor to continue to push the landing gear down even though it is already down and every time the spring extends the problem continues to repeat until the power is cut off." Foothill put the plane on jacks and has still not been able to recreate the problem. This makes sense because during our flight the noise only began after we were on the ground, not in the air. Worth mentioning is that my last flight was an IFR checkride where we shot three approaches in a row and extended and retracted the gear in the air twice with no issues before our final landing which was also totally fine and the landing gear came out and locked correctly. It was only after taxiing and sitting idle during shutdown that the noise began. The sound was so alarming that I do not feel safe to fly my plane again until the issue is properly identified and corrected. I am not a mechanic so my personal knowledge is limited when it comes to understanding this issue. I’m not even entirely sure it is related to the landing gear actuator or motor; or if either of these service documents (SI M20-112 or SB M20-190B) are even connected to this issue since I recently had it removed and shipped to LASAR for a complete overhaul (March 2021) and my actuator is a ITT LA11C2114 which is technically exempt from these service announcements. Have any of you heard this sound / had this problem before? Any feedback/advice would be greatly appreciated. Thank you.

We installed the new door seal on our M20C yesterday afternoon. We used the Knots2U seal based on what I read in @Marauder's New Door Seal thread. We bought their adhesive and remover. This evening we took her for a test flight with a short hop for a $100 enchilada plate and some cheap avgas. The new door seal is working better. The old HD seal was so poor that the front seat passenger shirt tail would get sucked out under the door. That doesn't happen any more. However... On final approach to our destination we noticed a baritone hum coming from the door. The pitch and intensity changed slightly with airspeed, and the sound became intermittent when encountering turbulence. Definitely a new sound, which means it is the door seal- that is all we have changed. On the trip back the noise was a bit louder- happening over a wider range of airspeeds, seems like whatever is vibrating is getting better at it. Upon landing, we inspected the seal and it is still adhered to the door. No obvious changes there. We installed it according to the instructions, which was to install the "L shaped" seal with the thick part adjacent to the a/c skin. Abut the door frame except near the hinge, when the seal shall be installed as near to the hinge as possible. The sound seems to be coming either from the area of the door hinge or maybe from the seal at the bottom of the door. Anyone dealt with this? I don't think that the seal is quite thick enough for our a/c. My guess is that the part of the L we installed by the hinge, that is not next to the skin or the door frame, is what is vibrating. My gut tells me to either backstop it with some intermittent beads of silicone, or thin HD door seal material. Please, somebody has to have troubleshot a solution for this issue already???

I did a flight with my CFI today. Landing at 3W2 I encountered a fairly violent nose gear shimmy on rollout, it dissipated taxiing in. I though perhaps I’d hit and imperfection in the runway and didn’t give it a second thought. There was no abnormality in the subsequent takeoff, but I encountered the same shimmy on landing back at home base. Again once I slowed down it went away completely. The tire is fine and at 30 psi. I can’t see anything obviously wrong with the gear. Sound familiar?

If you are experiencing a vibration in your mooney like I was you need to read this. One day my plane went from flying perfect to a nagging vibration. I checked everything EVEN the sparkplugs. We removed, inspected, cleaned and tested the plugs they passed; we put them back in the plane. We bore scoped the cylinders, balanced the prop, inspected the intake manifold, mags, carb, EVERYTHING. Then we took a step back and reinspected the spark plugs.....one of them was a little dirtier than the rest...we further inspected the cylinder for sticking valves....then my mechanic was regapping the plugs and BINGO! The wire had a tiny crack in it almost impossible to see with the naked eye but was noticable because the wire was "wobbling" slightly when he regapped it. New plug.......NO vibration back to running like a clock! PERFECT! I hope this message helps others that are on the brink of madeness like I was trying to solve this problem. I even had a Mooney mechanice take a ride and fly it and he said it was normal vibration.....If you notice a change in your plane don't give up or think it's in your head. These planes will speak to you when something is wrong and my plane did..The connections I failed to make during run up were: one mag would drop 100RPM vs the other only 50RPM's. This was telling me it was ignition related and I failed to notice. I was asked what happens when I did a mag check and I said it was normal...lesson learned. I hope you all benefit from this..zoom in on the attached picture of the sparkplug you will see the crack.

A question to the more knowledgeable: The vibrations in my M20 C are not bad, but noticeable. So, I thought about changing the engine mounts, as I have no idea how old they are. What I do not know is if it would be possible to change one after the other (while keeping the engine where it is) or if the engine has to come off completely (and all the nice cabels and attachments have to be removed). Any ideas? Cheers Norbert