solder brake elbows?

[prkaye]

First, let me carefully don my flame-suit, in case this is the most ludicrous idea ever...
I, like many people, have had a persistent problem with weeping through the pipe-threads of the AN elbows in the brake master-cylinders. I used fuel lube on all of them, and really had to tighten up several after installation (the rule everybody quotes is hand tight plus up to one full turn... I've had to tighten them all more than this... approx two full turns after hand tight). Since then, all have been ok (no leaks), except for one (pilot's side brake, lower (high-pressure side) fitting). I recently replaced the master cylinder and fittings, and have tried TiteSeal, and most recently Permatex High Temp Thread Sealant (I know it doesn't need to withstand temps, but that's the product they had at the store). Once I get it hooked up again and give it a couple days I'll know if this worked.

So, here's the idea - if the leak on this fitting still persists, what about using a small torch and running a bead of plumbing solder around the joint? Presumably hardened solder would not be adversely affected by hydraulic fluid? Would the pressure of the brake fluid behind it pose a problem? Would the heat of the soldering torch melt or deform the aluminum fitting? Is there another reason why this is a stupid idea?

[Mel]

I've used Permatex #2 on pipe threads for over 40 years and virtually never experience leaks.

[prkaye]

DO NOT SOLDER!

Ok, but why?

[Larco]

No flaming allowed toward you or the airplane :-) Please do not try to solder the fittings! If the fittings leak they are not tight enough generally. Most seem to be afraid of over tightening the pipe fittings but if you have used THREAD SEALANT, (I perfer teflon based) to eliminate the chance of galling, and they still leak, they probably need one more scary turn. If necessary, turn the fitting back and fourth during the last turn. I've done many pipe fittings and still once and awhile have to go back and tighten one because of a slight leak.
FWIW- the cylinders do have internal O rings and I wouldn't advice using a touch or that kind of heat anywhere onyour RV.

Larry

[rocketbob]

Anyone reading this thread please repeat after me:

I will not use Fuel Lube to seal pipe threads.
I will not use Fuel Lube to seal pipe threads.

There, thats much better.

Fuel lube is a LUBE (duh) not a sealant. Otherwise it would be called Fuel Seal.

I swear by Titeseal, works great. As a SEALANT. Tite SEAL...get it?

[N427EF]

Proseal is another great alternative.
You can easily open them again if you have to.
While I observe proper torque values I think the values given for AN fittings
especially the pipe thread ones is way too loose.
However, an over torqued B nut is more likely to leak and fail than an under torqued one.

[Wayne Gillispie]

Soldering aluminum is difficult. I do it on aluminum condenser and evaporator coils occasionally. You have to have itvery clean, use the proper flux and solder. Like others said, don't try it on a plane.

I use leak lock by high side chemicals. Good for 400F and 10,000 PSI. Get it at your local hvac dealer or distributor in 1.3 oz tubes.

[chaskuss]

Originally Posted by prkaye

Ok, but why?

Because in all likelihood, you will warp the bore of the master cylinder. You would in effect, simply trade one problem for another[even worse]. I like Permatex pipe dope with Teflon. Bob's favorite, TiteSeal, is another good one.

Charlie

[Av8torTom]

Don't believe the typical tin-lead plumbing solder will bind to aluminum. There are welding materials for aluminum of course, but not all alloys can be welded, and you would probably have to remove any anodized finish. I would use Tite Seal

[RV6_flyer]

Originally Posted by prkaye

Ok, but why?

Solder will not stick.
Heat will ruin the o-rings in the master cylinder.
Heat may start a fire with the hydraulic fluid.