[caddor38]

Guys,
I am having a heck of a time attempting to get my brake lines sealed at the master cylinder. I was wondering if any of you have encountered the same issue? The two brake line connections at the Master Cylinder to the proportioning valve has a tiny leak. I dry off the lines and come back a few minutes later and drag a completely dry paper towel across the fitting threads and where the line comes out of the fitting and there is a ever so tiny moist spot on the paper towel and there is no dripping so far, but over time this cant be good. It's not even a drop, however my expectations is that the fitting will be completely dry? I have gone through three sets of lines and they all look good and two master cylinders,
I performed the tightening method where you tighten it a bit and back off 4 times and retighten, but I cant find the root cause of the problem.

[rolling money pits]

As I’m sure you’re aware…the threads do nothing for sealing.

Lines pre-bent or did you make them yourself? Are they SS, parts store bundyflex, or nicop? SS line * can be * notoriously hard to seal due to being so hard relative to the others. What do the line seats look like in the MC?

If I’m reading your post correctly, you appear to have a tiny sealing issue at the seat.

[Sirrotica]

If you want to sidestep all the pitfalls of stainless, and steel lines, I highly recommend the Nicopp line. They are simple to form, and flare.

The one drawback is they are a different color than OEM lines, so for a correct restoration you'd probably be docked points in a judged car show.

The only surefire way to do the flares on stainless, and steel is with a hydraulic flaring tool, 2-$300 for a good one.

Another alternative is flare gaskets made of soft copper that go between the flare and the seat, to seal a leaking flare. They are made in 3/16".

Link to Parker flare gaskets:

https://www.amazon.com/s?k=flare+gas...f=nb_sb_noss_1

You mention that 3 sets of prebent lines have already leaked, you might take a magnifying glass and look closely at the seat in the M/C to see if it's damaged or cracked. That seat is the common denominator of the leak.

Hopefully one of these suggestions will get your leak to stop.

[caddor38]

Hey guys thanks for your response. Yeah i just ordered the 1/4” copper flares because the lines are slightly bigger than the 3/16. Its the lines from the master cylinder to the proportioning valve? If i made a mistake there please let me know.

I previously had a master-cylinder that was a disk to drum master cylinder, but i converted to all disk brakes. I did notice the disk to drum Master cylinder had smaller openings than the disk to disk master cylinder where the fittings connected.

I hope the flares will work but just worried about using the 3/16 or 1/4 flare?

[caddor38]

Originally Posted by rolling money pits

As I’m sure you’re aware…the threads do nothing for sealing.

Lines pre-bent or did you make them yourself? Are they SS, parts store bundyflex, or nicop? SS line * can be * notoriously hard to seal due to being so hard relative to the others. What do the line seats look like in the MC?

If I’m reading your post correctly, you appear to have a tiny sealing issue at the seat.

Yeah pre-bent steel? The line seats look okay but the holes are little larger in diameter than my original master cylinder that didnt leak. I ordered 1/4 cone pieces as mentioned in my post and hope thts the right size.

[JLMounce]

Check the depth of the threads in the master cylinder. I have seen reports that some new masters are not threaded deep enough which causes a false seal.

Probably not likely, but worth checking.

[GtoFM]

The flare gskt should take care of the imperfect flare problem and may also compensate if the threads are not tapped deep enough. The gskt should not interfere with the sides of the MC opening so don't force it. It should be the same size as the flare on the tubing. Get the 3/16" if in doubt.

[Sirrotica]

On GM vehicles the line that runs to the rear brakes is usually 1/4 inch, and the front lines are usually 3/16 inch. Thats not a hard, and fast rule, but more times than not that's what sizes GM used.

[NeighborsComplaint]

I've made my own lines with NiCopp and they are easy to form and even a mediocre flare will seal due to the crush you get with the soft material.

The steel lines that come packaged with no-name master cylinders from you-know-where quite often have irregular flared surfaces and some just won't seal because the steel doesn't crush. I had a fuel line with one fitting that would not seal and used a copper, tapered seat crush washer between the seat and fitting to seal it up. They are made by Parker and come in the typical brake line sizes.

Amazon sells packs of 10 but If I recall correctly, they sell them individually at NAPA .

[caddor38]

Okay guys, after about two weeks of cursing it appears the brake line leak issues between the master cylinder and the proportioning valve have been resolved. Thanks to you guys I purchased some of the copper sleeves from Amazon and Earls sleeves from summit. The Summit ones did not work and I only got 4. The copper sleeves from amazon finally worked after a couple of attempts and I hope to never loosen my brake lines again for the existence of the car.