Master Cylinder Copper Washer leak

Corvette1974

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Hello,

I recently installed the brake remote reservoir kit, and ever since then the master cylinder cap has been leaking at the crush washer connection. I have cleaned the mating surfaces and even completely sanded down the crush washer so it has no imperfections, yet it still leaks. I cannot really clean the surface of the master cylinder without removing it, and am trying to avoid that.

The leak is very slow, but it still leaks regardless. I cannot seem to find a crush washer anywhere for sale, either. Any ideas? I really don't want to pull the master, because I do not have a rebuild kit, and if it is off I want to rebuild it...

Please let me know.

Thanks,
Will
 

SCSG-G4

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Have you tried annealing the copper washer? IE, get it cherry red and drop it in cold water? Copper work hardens and becomes difficult to conform to other surfaces. The annealing restores the softness long enough to tighten it down.
 

FLYWHEEL

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Mine seeps a bit, but not enough to worry about. I think if I start messing with it, it will probably leak more.
I read on here about someone using a 1 1/4 square shoulder o ring from a plumbing supplier instead of the copper washer with good results. So it might be worth a search.
 
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63C20

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We learned early on ALWAYS REPLACE THE CRUSH WASHERS, we have a couple of Air Force Deuces, which have more than their fair share of these things. Fortunately the 1/2" crush washers are available from Pep Boys or NAPA as replacement oil plug washers. My brother's truck has a very slow, but aggravating leak that we need to address when we hit the lottery and can afford DOT-5. (just kidding, the MC needs to be topped up maybe monthly) We are lazy and will replace the washers when we rip off the front wheels and replace the seals, boots, slave cylinders, seals and brake lines
 

Bill W

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Mine seeps a bit, but not enough to worry about. I think if I start messing with it, it will probably leak more.
I read on here about someone using a 1 1/4 square shoulder o ring from a plumbing supplier instead of the copper washer with good results. So it might be worth a search.
DITTO
Back when I was installing my remote reservoir I bought two of these o-rings at the hardware store and put one in a container of silicone brake fluid for 3 months just to make sure it was compatable, the other one been on my deuce master cyl cap for years now.
 

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73m819

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.I got some crushable hyd. gaskets from a CAT repair tec. that took care of my master cyl. cap gasket leak, wish I had thought of the plumbing gasket..
 

Corvette1974

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Thanks for all of the great responses. The annealing idea is an interesting one. Might try that out haha I may have slowed the leak down to a very small rate, still have to check. I tightened the cap literally as tight as I could make it. Still need a new crush washer though....I will cross that bridge when I rebuild the axles/brake system.

If anyone finds a source for this crush washer, please post up so we can all order one! I cannot find one locally for the life of me. The plumbing washer is a great idea - but I cant find one of those either...

Will
 

Corvette1974

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The copper gasket actually "crushes" down so even if you sanded it to a mirror finish it still will not seal. You need a new copper gasket.
I agree, but I think it helped. You could see massive imperfections in it. Stop gap solution at best, though. I know I always replace the crush washer when doing a brake hose or similar, but how many "crush cycles" can a copper washer normally take?

Have you tried annealing the copper washer? IE, get it cherry red and drop it in cold water? Copper work hardens and becomes difficult to conform to other surfaces. The annealing restores the softness long enough to tighten it down.
Would an Oxy torch be too much, or just stick to a propane torch?

Will
 

rustystud

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I agree, but I think it helped. You could see massive imperfections in it. Stop gap solution at best, though. I know I always replace the crush washer when doing a brake hose or similar, but how many "crush cycles" can a copper washer normally take?

Only one cycle. Use it, replace it. I know most people don't replace there oil drain plug washers (which they should) and they seem fine. There are also other washers we always seem to reuse, but in hydraulic fluid and brakes and other areas that see pressure (even the low pressure of the master cylinder fill) they will leak if the copper washer is not in the "exact" location it was crushed in.
 

bonedoc

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I had the same issue with mine last summer when I replaced all my master cylinder, airpack, brake lines and all my airlines. I ended up using a plumbing o-ring in place of the copper washer. It worked great. Best part is you don't have to crank the lid down as tight either. Then I added some other parts to allow me to attach my remote reservoir line.

The first pic shows how it originally was set up. What I didn't like was 2 -fold.
1. When attaching the remote reservoir line, it is a pain to bleed the air out of it.
2. to make it easier to bleed the brakes and not have to remove the reservoir.

The way I set up gives me a shut off valve. and a plug that can be removed to bleed the air out of the remote reservoir line or bleed the brakes.

This combined with the rubber o-ring has stopped all seeping or leaks from the top of the reservoir. Now everything stays dry and if it isn't...I know there is a problem.
 

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Corvette1974

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I agree, but I think it helped. You could see massive imperfections in it. Stop gap solution at best, though. I know I always replace the crush washer when doing a brake hose or similar, but how many "crush cycles" can a copper washer normally take?

Only one cycle. Use it, replace it. I know most people don't replace there oil drain plug washers (which they should) and they seem fine. There are also other washers we always seem to reuse, but in hydraulic fluid and brakes and other areas that see pressure (even the low pressure of the master cylinder fill) they will leak if the copper washer is not in the "exact" location it was crushed in.
10-4 I tend to replace all copper washers when they are easy to get. Oil drains come to mind. I *think* I got my leak to stop by making the cap even tighter. I am not going to disturb it until I delve into the brake system and rebuild everything.
 

Corvette1974

Member
493
1
18
Location
Pennington, NJ
I had the same issue with mine last summer when I replaced all my master cylinder, airpack, brake lines and all my airlines. I ended up using a plumbing o-ring in place of the copper washer. It worked great. Best part is you don't have to crank the lid down as tight either. Then I added some other parts to allow me to attach my remote reservoir line.

The first pic shows how it originally was set up. What I didn't like was 2 -fold.
1. When attaching the remote reservoir line, it is a pain to bleed the air out of it.
2. to make it easier to bleed the brakes and not have to remove the reservoir.

The way I set up gives me a shut off valve. and a plug that can be removed to bleed the air out of the remote reservoir line or bleed the brakes.

This combined with the rubber o-ring has stopped all seeping or leaks from the top of the reservoir. Now everything stays dry and if it isn't...I know there is a problem.
Looks good. What are the specs on the plumbing o-ring you used? I don't want to reinvent the wheel when yours seems to work very well.
 
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