Problems!! Brake line bleeding and leaks

[Whitephrog]

I'm bleeding my brake lines today with a Mityvac. Not as easy as I had hoped but I was making progress. Tehn I noticed that I had a few small leaks and one not so small. One of the fitting to the four way switch is leaking a bunch. Tightened it a bit more and it still leaked. Can/should I use Teflon pipe tape on those fittings?

 

[Deleted member 8987]

No. Teflon or any other sealant will work on threads, but the leak will come out from the pipe-to-nut gap.
If it's leaking, the end of the pipe is not right, or damaged, or the block is damaged in the seat area.
Bubble Flare, should be, and if it's inverted, will not work.
If you did a 1/2 inverted, it may not quite be extended enough to seal (BTDT).
When doing bubble flares, cut the pipe, then with a round jeweler's file, clean out the "curl" inside until the opening has zero curl, i.e. you can see the straight line to the inside of the pipe, or it won't bubble right.

Use a drop of brake fluid or assembly lube for brakes when using the tool!

 

[Deleted member 8987]

Another thing I have seen is 50 years of overtightening will flare the straight end sides of the nut...to the point it bottoms out before the pipe is tight.
I have reworked these successfully in the past with a fine wheel on a bench grinder and followed with a file.
The straight sides are NOT a sealing surface.

Dave

 

[dfwip]

What Dave said.
If you want to become an expert in getting brakes sealed, make up a set of lines out of stainless. The stuff is just too darn hard. I think with standard soft steel lines, as you tighten them the first time, they "conform" and seal. Let me tell you, stainless doesn't.
That being said, your brake lines do NOT seal at the threads.
Suggestion...loosen the faulty fitting and bent the line just slightly so that it enters the socket a bit differently. Then tighten. This will often fix the problem. I have also had luck LIGHTLY file-shaping the flare.
Good luck.

Paul

 

[Whitephrog]

Thanks to you both. I'll try a bit of bending today. These are new steel lines that I had Royal Brass and Hose make using the old lines as a pattern.

 

[Scott_Hower]

Also double check the seat in the union. Sometimes the flare cuts a crescent into the bottom of the seat. BTDT and no amount of tightening will get it to seal.