How tight for 90 degree brake cylinder elbows?

[JonJay]

I use fuel lube and have no leaks. Unless they match up perfectly in orientation the first time you tighten them, which is rare, you will need to "work" them into position. This is done by backing them off a quarter turn, then tighten, then back off, then tighten, just like when using a tap for threading. You may need to remove them and clean the threads, then try again. Once you get it into position do not back it off or it may leak.

You may find a fitting that will not allow you to get it into position. Try another fitting. They are not all machined alike.

[RV10Rob]

Thanks, Jon... what you described is exactly what I did. When I did it originally, one leaked, so I tightened it pressed on the pedals a bunch, with no problems. After I did the first engine start last weekend, though, I noticed a couple drops on the floor from both sides, so I was probably pushing harder.

I'll take them out and clean the threads, but will be looking to use something more "robust" on the threads this time.

-Rob

[John Tierney]

I had heard that Bakerseal should be used on brake lines and E-Z Turn on fuel lines.
http://www.aircraftspruce.com/catalo.../bakerseal.php

[JonJay]

Originally Posted by RV10Rob

Thanks, Jon... what you described is exactly what I did. When I did it originally, one leaked, so I tightened it pressed on the pedals a bunch, with no problems. After I did the first engine start last weekend, though, I noticed a couple drops on the floor from both sides, so I was probably pushing harder.

I'll take them out and clean the threads, but will be looking to use something more "robust" on the threads this time.

-Rob

I had the same thing and thought it was the pipe thread but it actually was the tubing/b-nut fitting. It is very hard to tell where the leak comes from as the fluid can run down and pool around the pipe thread making it look like it is the culprit.
Also, the master cylinders can leak a touch from the seal when you first start messing with them. I had a small leak on one cylinder but after a few pumps it cleared itself up.

[vmirv8bldr]

Like the OP, I used EX-turn. The left master cylinder leaks at the fitting. I have not installed the forward baggage floor and have great access, and I can see the fluid coming out around the fitting, so I know this is where it is coming from. I drained the brakes and tried permatex with the same problem. After doing a few searches here, it seems Loctite 567 or Bakerseal are the preferred sealants, but it also seems that several folks have had success with EZ-Turn. I'm going to give it one more shot and it if it isn't working then, I'm going to swap the MC out and see if that does it.

By the way, I went ahead and swapped sealant on all NPT fitting on the MC. This is still the only one leaking.

Also like you, I have also gotten quite good at filling the brake lines.....

[TS Flightlines]

Teflon tape isnt a good choice, for all the above reasons. BUT, NPT sealer with teflon ( the paste) works well. When you are doing your mock up assembly, mark the cylinders where your AN822-4D's should point (sharpie). Seal the fitting, ans after hand snug, you should be able to get them to tighten up and index to the mark. Be careful on aluminum to aluminum, and really cranking on them---yep you CAN break a fitting, or strip the cylinder.

Ive been using this teflon paste for years in alot higher pressure applications than RV brake systems with no issues. Its all in the preparation.
Tom

[Jerry Wilcox]

This seems to be a never ending subject, I have been working around aircraft for 40 years and have always used fuel lube on pipe threads. This was from instruction by my first boss who was an experienced and military trained AME, A&P. I learned years ago that you do not put aluminum pipe fittings together dry unless you want to order new fittings. I feel that most times pipe fittings leak they are not installed tight/deep enough. I also think that pipe fittings seal because of their design, taper, and not because they have a compound of some sort applied. The reason for applying fuel lube, EZ seal or whatever you choose is to lubricate the thread and allow it to go together further and tighten/seal deeper into the taper.

[vmirv8bldr]

My hangar neighbor (Zenith builder - DAR inspection this week!) had some Bakerseal that he used on his plane. He got it from Aircraft Spruce and is enough to last several lifetimes. It looks very similar to the paste compound you can get in the plumbing section at any hardware store, but says specifically that it is made for use with hydraulic fluid (and many other things.)

I took the leaking fitting out and cleaned it very well with a brush and some solvent. I also cleaned the female thread in the same manner until they were shiny. I then applied a liberal amount of the paste to all but the first thread and installed it. Reconnected everything and filled it.....Voila! Leak free.

On to the next item on the list....

[Michael Burbidge]

What a pain. The bottom fitting on one of my pedals leaks! I originally used Fuel lube. Then I tried permatex #2, but it still leaks. And I've not figured out how to efficiently put the brake fluid back in. Painful, painful!

I think I'll try Bakerseal. AircraftSpruce doesn't seem to carry it anymore. Where did you get it from?

Michael-

p.s. Just doing a little complaining.

[BillL]

If your NPT thread is leaking, I believe it is 1/8" NPT pipe. A typical tap and die set has this tap in the set. Thread it in and turn maybe 1/8 turn and then see if it seals. EZ turn is a lubricant not a sealant, so go back to #2 permatex or #3 which ever you have on hand. Sometimes a rapid production threading for NPT leaves an axial ridge line where the tap stops and that is where the leak initiates. Especially if it is a single point threading tool. Just honking on it with lubricant might work but it also might break the housing. It IS tapered! So . . . not recommended.

Good luck