EricJ

Could you tell whether it is binding at the top or at the side latch? Inspect both of those carefully at the frame and on the door the next time you get a chance.

There's a recipe in the M20J SMM, but Spruce used to sell a mix that (iirc) is what we used. I can't find it on Spruce any more, you could still mix up the stuff in the SMM. Very mild soap could potentially be used and then rinse the crap out of everything when you're done, too, if you're careful where it goes. Edit: Spruce still sells this stuff, which looks like it'd be reasonably suitable (pH = 6.9-7.5). https://www.aircraftspruce.com/catalog/appages/detectorfluid08-12291.php

You can also get an Avidyne IFD 440 and slide it in where the 430 is. That's more expensive than buying a used unit, but much less than paying for a new installation of something else.

Non-pressurized airplanes generally leak like crazy. If you ever pull your carpet up you'll see there are huge gaps and holes all over the floor, built that way from the factory. The belly isn't sealed, either, so air can flow through the belly and floor pretty easily when it wants to. Positive angles of attack tend to be worse in most airplanes, I think for the reason that the belly/floor is so leaky, and it can just get through more easily. At cruise it just slips by more easily and the vents bring in more than can leak in, so for many/most airplanes it seems like CO goes to 0 or close to it in cruise. Mine used to be worse than it is, and the main thing I did was just cover up some of the holes under the carpet with foil tape. It got a lot better, essentially good enough that I don't worry about it any more since it's 0 at cruise and not very high the rest of the time. We used a leaf blower and some soapless bubbles on a friend's (non-Mooney) airplane to find and fix a ton of leaks. It still leaks, just tolerably now.

Usually one expects positive pressure on the doors, not negative. The M20J/K gear pulls down with aero because the inner doors are canted outward in transit, but you don't have those. There isn't much of a spec on how tight the doors have to be against the bottom of the wing, so I don't think aero is your problem. If it was, it'd be seen across many Mooneys that don't have properly rigged doors, i.e., it'd be a fairly common problem. If you're already finding the doors snug against the bottom, I suspect that's not the issue. You might try turning the power on and pulling on things or bumping on them while it's on stands and see if a relay isn't turning on intermittently or something. This seems like a pretty unusual problem. If you have an airspeed switch, maybe that's involved since it seems airspeed dependent. That may involve a mis-wire, but I think that sort of thing may be in play.

Have you tried pulling on the gear legs while in the up position when on jacks? If it moves, pop the belly off and see if the jack screw is back-driving somehow. It may be a bad relay or something dumb like that, or components on the jack screw or actuator gears may be worn that allow it to back-drive.

If you use it sensibly it helps you look outside more, and more effectively. If it doesn't, you're not doing it right. Why do you use an airspeed indicator? Just use the feel and weight of the controls and the sound of the air flowing over the airplane! THE ASI IS A DISTRACTION! IT TAKES AWAY FROM YOUR AIRMANSHIP SKILLS! YOU SHOULDN'T EVEN HAVE ONE! Why do you use a radio at an uncontrolled airport? Aren't your eyes effective enough to see all traffic? STOP USING YOUR RADIO! LEARN TO LOOK OUTSIDE! EXERCISE YOUR SKILLS! YES, I'M KIDDING! You should use every tool available that improves your situational awareness. ADSB goes a long ways toward improving SI, but you can't just stare at it and people who think that's how it's used are trapped in cold darkness.

In this case, though, if the other aircraft had been using their ADS-B as they approached the airport it would have increased the likelihood that the Cessna would have been aware of them, which is what it's there for. If the other aircraft had been using ADS-B-in they'd have had a higher likelihood of being aware of where the Cessna was as well. I think the glitch you saw may have been due to the display device rather than ADS-B itself. It seems like some displays will hold their last known display point for a transmitter or apply some predictive algorithm (Kalman filter maybe?) in the event that it misses a transmission or two. Those sorts of processing artifacts will likely be different from EFB to EFB and display to display. I've seen disagreements between my in-panel traffic display and my EFBs, or even between the two tablets I use with the same EFB software. It's not a perfect system, but it is a huge benefit in improving situational awareness. My home airport is extremely busy, and even just when holding short of the runway waiting to take off it's very useful to be able to see the traffic in the pattern and the aircraft on final to be able to anticipate a gap when they'll let me out. I'm very puzzled by people who aren't able to use the information to improve their situational awareness.

Yeah, I recently spent a bunch of time tracing several generations of obsoleted part number to find a gasket. The part number in the IPC has been obsoleted and replaced, that part was obsoleted and replaced, etc., etc., for several generations. Finally found what an equivalent current part number is and there is still a supplier since it is still used on some corporate aircraft. Many times the parts are just obsoleted to the point that nobody makes it any more since the technology itself is obsolete, like the fiberglass materials specified for M20J cowls. Keeping old airplanes flying requires some creativity sometimes. The parts catalog for the aircraft is usually the best place to start, though.

For some items there's a part number like that, and it's a Mooney part number if it's something that the factory made or supplies exclusively. For the nut plates if Mooney ground the drain gaps into it, it's not something you can buy off the shelf so it has a Mooney part number. The trick here is to find the standard part and maybe just grind the drains into it yourself. For many items there's a standard part number, like for a nut or bolt or washer or bulb or whatever. And for many other items there's a manufacturer specified and the manufacturer's part number. The catalog is really useful that way to sort out what's needed, but in this case it's something that was evidently modified at the factory from a standard part, so it has a factory part number.

Yup. Was recently helping with an airplane that is grounded until an avionics fan is replaced. The KOEL requires it, even for VFR day operation. It's a typical computer chassis fan, but it's $1500 from the OEM. Not a Mooney.

What does it do on jack stands? Does it close on jackstands?

Generally not. Higher oil temp in this case may just be a symptom of inefficient air flow in the cowl, e.g., baffle or baffle gasket leaks.

That's not very bad, so I suspect checking the baffle gaskets, baffle condition, etc., will be useful. Your oil temp seems a bit high, too, so I suspect you just have leaks in the baffles or baffle gaskets. You can put a flashlight in the oil hatch and see how much light you can see from the front inlets to get an idea of how well the baffle gaskets are seating against the cowl. You're getting decent speed out of it, so the engine is running fine.

That's sometimes helpful for carburetors to more evenly distribute the mixture, but not so much for fuel injection. The other issue with many carburetors is the "economizer" circuit that richens the mixture more at WOT than if pulled back a bit.