The Cessna 120-140 Association Forum

Can anyone identify this. The top screws on. I bought a seal kit that I thought would work but it was wrong.
Also the threads are messed up on the elbow. Anyone know where I can find a new one. It's a -3 flair X -4 Oring boss (AKA SAE).

That's the classical original cylinder on the 120/140. Suggest before you think new _$$$$$$- get the right O ring and replace the elbow and try yours. It was originally set up with parking brake capability which has obviously been removed - note the slot in the "hat" section of the screw-in cover - that was where the arm was located that engaged the slotted stem to keep pressure on the brake for parking. System caused problems for some, so was removed to preclude accidents!

John C et al will be on and give part # for proper O ring, etc and their recommendations.

Big Edd

AN6227-7 or MS28775-012. The cylinder is a very simple design and the o-ring is the only wear part. There is a little pin that cocks the o-ring at the top of the stroke to allow fluid in and out of the reservoir. The o-ring takes a set over time and doesn't seal properly.

The elbow fits to the cylinder with an AN902-4 gasket, which, if memory serves, is a rubber washer, not an o-ring, with a flat cross section.

Thanks for the info guys. Just what I needed.

Oh, yeah, the elbow is AN921-4D and the nut is AN924-4D.

Can anybody tell me the part number for the brake master cylinder? As well as a good aftermarket replacement.

Thanks!!!!

Goodyear 95-3681, Cessna PN 0411058. I think the masters from a 150 will mount right up.

As stated above, there's not much that can go wrong with the originals.

Unless it's rotten it should work with a new O ring. Very important that the fill plug has a vent hole drilled in it, about .050 works.

For 140As in serial number range 15200 - 15375, the IPC mentions that the filler plug is plastic (0411058-9).

Three questions:

Have these mostly been replaced by brass or aluminum 1/8 pipe thread plugs?
Should this plug also include the small vent hole in it?

Apologize to sound vague. I am going to be working on an A with brake issues and I forgot to take photos of the master cylinders on the airplane when I saw it last.

Thanks,
Elliot

I can't say as to whether they have been mostly modified. I see no reason you couldn't use an aluminum one. No reason I can see to use brass instead.

Yes, they must be vented. If the aluminum plug has a drilling for safety wire, just drill up from the base of the plug to intercept the cross drilling.

MS20913-1D