I have this friend..

I am hoping the plug for the brake fluid resevoir (located above the battery) is a 1/16th in NPT thread. Will find out after lots of driving

You can infact do this with a 2ft extension 3/8" drive and a 9/16" crowesfoot. Grind down the crowsfoot with a dremel to make it as skinny as possible You can actually access it from both the right and left side of engine which is useful because you can only move it one flat a time. Note, this is with a open-end crows foot not a modified box-end crows foot.

Let me save someone some time in the future... 1979 M20J Fuel gauges reading half full when tank is full, but only after being drained. I know this is absolutely the inboard fuel sending units being stuck. It is not an electrical problem. Here are some clues. 1) It is repeatable to almost exactly half. There are two sending units per tank in series. Assuming conservative failure of open circuit a wiring issue would tend to make infinite resistance and read empty, maybe a poor connection could read a higher-than-normal resistance. However, reading exactly half or 16ish gallons on a 32 gallon tank and having that repeatable. It is very suspect that a poor connection would be just the right amount of resistance for this indication. 2) It happens specifically when the tank is run very low or drained. 3) In my case when I drained both tanks that indicated full, and then immediately filled back to top, they suddenly both indicated exactly half full. 4) The number one reason I KNOW this to be a stuck sending unit is because a $32 amazon borescope wired tied to a 3mm aluminum wire from amazon allowed me to go in from fuel tank fill hole, find the sending units and touch the sending unit arm. Eureaka, arm popped up, did to the other side, both tanks full. Should I replace the sending units? well, here are some thoughts. : 1) Conservative fail. It won't cause you to run out of fuel, only make an unnecessary stop. 2) Likely to resolve itself on your first sharp bank. 3) It's repeatable but ONLY by draining my tanks to the very bottom. If you don't drain your tanks to below 4 gallons you will not likely see this, and you should not be flying with 4 gallons of fuel anyway. E.g. calibrating a Garmin G3X touch to work with OEM sending units (btw they have to be in voltage mode not resistance mode even though they work via resistance). 4) I experienced this many years ago on the same aircraft (drained to flush tank) and a borescope on aluminum wire worked then too. 15 yrs later draining the tanks I had to purchase a new scope. Note1 the inboard sending units are on a rod connected to a small circular panel bolted to the vertical inboard edge of the tank e.g. accessed from inside. I know this from looking inside the tank with a borescope. Note 2 not changing the sending units is not about the cost of the unit, it's about opening up a can of worms by breaking a seal. Also my cal curves look very nice, I don't believe this is a problem worth the effort to fix at the moment.

Hi, 1979 M20J spongy left brake. I have dual brake sets. The last time this happened I bled about 1/2 gallon top down and solved the problem for about 2 yrs. My method was to have someone pump the pedal down until pressure, then open and close the bleed screw on caliper (acting like a one way valve) then repeat. It was painful process, but resulted in very solid brakes. I am considering bleeding bottom up this time (e.g. pressure pot) For a collection container connection, does anyone know the thread and diameter size of the plug in the brake fluid resevoir over the battery? The Mooney part number is 850009-000 plug, filler I would just measure it, except it is 4 hrs of driving to get to the plug. Trying to make something with a barbed fitting so i can connect to a tube obviously. Any help appreciated.

This hose is a ms28741-4-0150 And it has fire sleeve crimped in place access is very tight. Can i remove this with a 9/16in open end crows foot and extension? Should i try to get 1/4in drive for smaller tool? (Its a 2 hour drive each way to airplane want to be prepared)

All, great discussion btw! Pun intended here is more fuel... My friend would love to get an STC. Under the impression it is not possible with a 79 M20J. Does anyone know if this is true? (Lycoming 200hp IO-360 A36BD I believe. Question: regarding boiling fuel (I find it hard to believe fuel at 4500 ft would boil with slight suction head (mechanical pump is aprox 1 foot above mean fuel level?) But in the event it did, Isnt boost pump even lower? Need to look at a parts manual. 12000 ft might be more of a concern. Although by the time u got to 12k on 100LL u probably would not have hot fuel or at least in the lines from fuel level to pump inlet assuming you are not taking off from colorado). Someone mentioned different blends based on season. Question: if it is advertised as ethanol free and you test it for ethanol free, and MTBE is no longer allowed. What else are they adding that is a concern? I was under the impression that gasoline with no MTBE or ethanol was not going to hurt tank sealant or internal seals hoses etc.. Regarding longevity of fuel, any thoughts on using "stable" its amazing how well it works with boat fuel storage. Not that I would imagine leaving in tank for long time. Regarding cost savings. A round trip flight from say Georgia or Carolinas to NY or Vermont the savings is easily enough to make it cheaper than a commercial flight. Its can easily be $3.00 cheaper per gallon. Agreed none of this is worth it if an accident is caused. On the other hand if 100LL becomes scarce this is what will happen. I imagine if user fees for FAA services occur things are not going to get safer either. I agree it would be safer to use 100 LL. But.. It seems it is possible to use auto fuel if you are extremely careful and only use it in certain circumstances.. And.. It would be safer to fly an aircraft with fixed gear. Yet people fly all the time with retractable gear. Anyone else ever have a failed gear motor? It would be safer to fly only in the day time. Why would anyone fly at night? It would be safer to not fly IFR It would be safer to fly with two engines. Who would risk flying with only one engine? Any twin owner would first ask you where your second engine is before asking what is in your tank. It would be safer to not fly at all. It might be safer if all general aviation went away Its all calculated risk. Is flying 93 octane ethanol free the most dangerous irresponsible thing you can do with your aircraft? Does anyone know if this is a statistically significant cause of crashes? Probably not a valid question because no idea how many people are actually doing it.

Interesting responses. Happy to hear my friend is not the only one. Yes 50 L.O.P. Where can we get 100 LL for $4.00? In upstate ny it is $5.30ish.. carolinas it is $4.65-6.69 Miami $8 or $9? Last flight was closer to a $55 savings. Plugs seem to fowl less? Could be imagination. Correct me if wrong but isnt "mogas" technically aviation sanctioned fuel similar in spec to automotive and sold at airports? I thought it was slightly different from gas purchased at pump on street. Not sure as It gas been years since I have seen any non 100ll sold at airport..

Fyi I have this "friend.." Runs about 20% 100ll and 80% 93octane no ethanol automotive fuel in left tank. Take off and landings on right tank with pure 100LL. He has a simple ethanol tester uses to prove no ethanol. Cruise at 65 percent power 50 deg rich of peak. Runs great.. no issues. (I would never do this of course) but my friend... Anyone else have a friend with similar experience? IO360 A36BD?