Brake Lines questions

[WingedFrog]

Just working on brake lines set-up, I have the following questions:

- Screwing elbow fittings into master cylinders: After 2 and a half turn I feel resistance and don't want to force an additional half turn to get the elbow properly aligned. After adding thread sealant and letting it cure, I feel the elbow can move under light pressure - will I get leak under pressure? Should I screw the elbow 1 more turn?

- What is the torque for brass brake line fittings that screw on the elbows?

Thanks

[Walt]

Originally Posted by WingedFrog

- Screwing elbow fittings into master cylinders: After 2 and a half turn I feel resistance and don't want to force an additional half turn to get the elbow properly aligned. After adding thread sealant and letting it cure, I feel the elbow can move under light pressure - will I get leak under pressure? Should I screw the elbow 1 more turn?

Yes you will have a leak and Yes you should go one more turn... pipe thread fittings need to be TIGHT!

[dick seiders]

Jean-Pierre, those fittings also need blue (medium) loctite to prevent leaking.
Dick Seiders 120093

[WingedFrog]

Originally Posted by dick seiders

Jean-Pierre, those fittings also need blue (medium) loctite to prevent leaking.
Dick Seiders 120093

Dick, the instructions say to use a small amount of thread sealant - I use Permatex with PTFE which I used also for the fuel lines: is Loctite better?
As according to Walt I have to tighten all my elbows, I will have to clean the thread and put fresh sealant, a good opportunity to use loctite if it works better.
Any advice on the matter is appreciated.

[yankee-flyer]

I installed all my brake fittings with what I thought was good aircraft sealant (EZTurn) and they checked out just fine during initial testing-- standing on the pedals as hard as possible. Then after the taxi tests I found brake fluid leaking several places. Fitting were already too tight to turn another full turn, so I had to remove every fitting (After the airplane was assembled),. remove the old sealant (which had gotten hard) reinstall with white Loctite fill and bleed the system again. Much less fun that the first time. Do it no while you can still get to the fittings easily.

Wayne 120241
N143WM

[rsipp]

I have found when installing these aluminum to aluminum fittings or aluminum into steel they tend to start galling and tightening before they have reached a properly tightened state. It seems to help to start the fitting in until starts to tighten, then back it out and turn it in again. You may do this a few times. (Sort of like tapping threads) With each successive re-tightening the fitting will go in farther and you should be able to find the clock position you need and a leak proof seal. Lub as directed in the plans.

Dick Sipp

[DonFromTX]

I use Loctite 567, which is specifically for brake fluid and threaded fittings. The Blue don't say it is ok with brake fluid. It also has some teflon in it to avoid the galling of threads (thanks to Joe Gores who found it for me).

[TS Flightlines]

the threads in the master cylinders and the fittings are pipe taper threads. The 2 tapers give a mechanical seal, and should have a thread sealant compatible to whatever fluids you are using. BUT---if you overtighten a male NPT into a female NPT port, you can enlarge the port slightly to where it may be difficult to seal, dispite whatever sealant you use. BUT--like Walt says, they have to be tight so they wont leak, and so the fittings will index properly. Once you've overtightened a NPT female port, you may not be able to re-align the fitting without causing damage to either the master cylinder, or the fitting. Be careful!
Tom

[WingedFrog]

It is clear that there is no fool proof solution which is what I was looking for .
My second question was not addressed: What is the torque for the nuts, part of the elbow assemblies that screw on the elbows providing a sealed connection between the elbow and the plastic pipe?
I expect this one to be fool proof!
Thanks!

[Tony_T]

Originally Posted by WingedFrog

It is clear that there is no fool proof solution which is what I was looking for .
My second question was not addressed: What is the torque for the nuts, part of the elbow assemblies that screw on the elbows providing a sealed connection between the elbow and the plastic pipe?
I expect this one to be fool proof!
Thanks!

Brake fluid leaks have been a problem for several of us because of using the wrong sealants. The brake manufacturer Matco recommeded the Loctite 567 in a previous thread on this subject. I had to drop the main gear support piece with the brake fittings out of the main crossmember when the plane was on the supports for the annual in order to reseal the fittings with Loctite 567. Not real difficult but much better to get it right the first time.

The nuts on the compression fittings are tightened hand tight then 1 full turn -- see the plans Section 5.

Tony