New Brake Master Cylinder Leak

[mgm60]

This seems pretty simple but I'm about to bust a gasket trying to stop this leak on a new Master Cylinder in my 36 Roadster. This started with upgrading the 48 Ford front brakes to the Boling Brothers 39-48 kit. While I was at it, I replaced the master cylinder and used the original outlet bolt, brass fitting and stop light switch. Leaked between the outlet fitting and new Master cylinder where pictured. Tried thread sealant on the outlet bolt and tightened with a BF Wrench. Leaked. Bought another new Master Cylinder, new outlet bolt, new outlet fitting and new stoplight switch. Used Permatex 54540 Hydraulic sealant and a couple of club members suggested I heat the copper washers so I did that too. Reinstalled. Leaks in the same spot. The bubble you see on the very bottom edge of the Master Cylinder is brake fluid.

Master Cylinder is located on a juice brake conversion bracket bolted to the X member and frame.

Suggestions?

[petehoovie]

Originally Posted by mgm60

This seems pretty simple but I'm about to bust a gasket trying to stop this leak on a new Master Cylinder in my 36 Roadster. This started with upgrading the 48 Ford front brakes to the Boling Brothers 39-48 kit. While I was at it, I replaced the master cylinder and used the original outlet bolt, brass fitting and stop light switch. Leaked between the outlet fitting and new Master cylinder where pictured. Tried thread sealant on the outlet bolt and tightened with a BF Wrench. Leaked. Bought another new Master Cylinder, new outlet bolt, new outlet fitting and new stoplight switch. Used Permatex 54540 Hydraulic sealant and a couple of club members suggested I heat the copper washers so I did that too. Reinstalled. Leaks in the same spot. The bubble you see on the very bottom edge of the Master Cylinder is brake fluid.

Master Cylinder is located on a juice brake conversion bracket bolted to the X member and frame.

Suggestions?

[19Fordy]

I bet your leak would be solved if you used brand new copper washers.

Here's an idea: Perhaps this sealant will work. Worth a try as it's resistant to gasolene.
May also work with brake fluid?
https://www.youtube.com/watch?v=IPhqDxApCwA

[Conrad Rossi]

Probably you have checked this already. I will check a) the flares for kinks or small nicks b) ensuring using the right oem washer as sometimes it could interfere with the tightness of the threaded nut, and c) replacing the washer in case you over tighten the flared nut. Thanks.

[Flathead Fever]

some of the old brake brass washers had a bunch of circles pressed into them or maybe they were machined into them that helped them seal. I know they existed because we had a box of them at the shop that had been there since 1950. I was a mechanic and sometimes I had the leaking problem on disc brakes when I used the new smooth washers that came with the calipers. I'd switch out the washers that came with the calipers for the original washers with the sealing circles and the problem was solved. A lot of parts already have the antileak circles machined into the cylinders or hoses so the smooth washers will work on them. Some of the new parts are smooth and don't have those sealing rings, a smooth surface and a smooth washer can leak. You might check to see if the master cylinder and brass "T" fitting have those machined sealing circles.

[mgm60]

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Also installed new copper washers on both replacement Master Cylinders. They are the flat washers from CW Moss.

[19Fordy]

Originally Posted by mgm60

Also installed new copper washers on both replacement Master Cylinders. They are the flat washers from CW Moss.

Do your brass fittings have the circles machined into them (as shown above) so your new copper washers can "bite" into the brass and seal the two mating surfaces?
Will applying Sealall to between the copper washer and brass surface help?

When you installed your flared brake lines into the brass fitting did you first apply brake fluid to the thread fittings ? I find this makes for a tighter fit as the threads aren't being assembled "dry".

[leon bee]

I anneal new washers nowadays as well as the old ones. Just hit em with a propane torch till they turn orange. When they cool you can feel the difference. May not be your problem, you'll get it sooner or later.

[Conrad Rossi]

Great tip! Thanks for sharing.

[Terry,OH]

I added a third washer and the leaks stopped.

[Newc]

Annealing copper washers is an old standard method. heat till good red and then dunk in water. Aircraft spark plug gasket washers- did hundreds of them. Newc

[38coop]

I had to use two washers to stop my leak.

[69a]

leon bee is correct! To anneal copper you need to heat it until it turns orange. The method of cooling it. Has no effect on its hardness. You can quench it in water or just leave it.

[deuce lover]

Washers like this?

[glennpm]

Originally Posted by 69a

leon bee is correct! To anneal copper you need to heat it until it turns orange. The method of cooling it. Has no effect on its hardness. You can quench it in water or just leave it.

Yes!

[51woodie]

I was helping my Grandson replace the calipers and brake hoses on the front of his '98 Dodge D250, and used the new copper washers that came with the hoses. After bleeding, we found that both connections to the calipers were leaking fluid. We found that the new washers were only half as thick as the originals, and that the fitting on the end of the hose came up tight to the caliper housing, before enough squeeze was put on the washer to make a seal. We annealed the old washers, used them, and problem solved. The fitting on your picture of the master cylinder seems to show there is no clearance between the fitting and the MC. I guess washers of half the thickness is cheaper to make than the full thickness of an original. Or, made in China with metric specs?

[petehoovie]

Originally Posted by deuce lover

Washers like this?

[mgm60]

Got new washers, annealed and did not use sealant this time. Reinstalled. Leaks from the same connection where the outlet bolt goes into the MC. Brake line connections never leak, always dry.
These washers are thin and smooth, don't have the rings on them like the ones Deuce Lover posted. But the brass outlet fitting has those circles machined into it on both mating surfaces. So when you tighten it does leave an impression in the copper washers.
Back to the drawing board. Will try doubling the washers as suggested. Somebody over on the HAMB mentioned using Stat-O-Seal washers but those I'd have to order so will probably do that too just in case.

[deuce lover]

If you can use the 2 (1 is new) I pictured PM me and I'll mail them to you ,Free.
PS they are 3/8 ID.

[tubman]

Several years ago I was able to source quality copper washers with concentric circles from Pegasus Racing Supplies.