Tinat

I sent off my master cylinder and wheel cylinders to get sleeved and cannot get the m/c to stop leaking. I have replaced the brass washers, brass block & bolt, and rebuilt it with a new master cylinder kit twice.
It seems to leak around the big nut.
Any advice would be so appreciated. At wits end here.
Wondering if I should have it magnafluxed for a crack?
Thanks so much.
Oh.....it's on the 1960 vette

Pilot Dan

Check around the M/C casting and fitting and the big nut to make sure
the casting is not cracked. I have heard on occassion that a casting can crack during sleeving.
Rare, but is DOES happen. Rule that out, and all that is left is the fitting and new copper washers.
Let us know what you find. Pilot Dan

emccomas

I have the same problem on a 56 M/C after it was sleved and rebuilt. I don't know what kind of shape it was in before the rebuild.

It is more of a seap than a leak. I have replaced the brass block once, and the washer set twice.

I am looking for an alternative that gets rid of the brass block and washer arrangement. Originality is not an issue for me right now.

I wish I could find an adapter that screws into the end of the MC, and the brake lines screws directly into that.

Redbird

Are the washers actually crushing/sealing? If I recall the machined surface on both sides of the block have a circular surface, and the washers crush into the grooves to seal the mating surface.

Tinat

I have seriously checked all of these and can't seem to find the problem. Should I have it magnafluxed?

56Heap

I had the same thing after I rebuilt a 56 master cyl. I used a 1/2" air gun with a 6pt socket and just gave the nut a few quick burps with the master mounted in place....problem solved .....must have been just enough to set the copper washers???

Redbird

Amen!

Pilot Dan

Here's a picture of a recent rebuild I did for reference:



First off, are you sure the leak is coming from the big nut and not the plug above?? Was the plug removed? Assuming that the leak is from around the nut, make sure the M/C surface under the nut is undamaged and smooth (and any old washer or material is removed) then place a single new washer under the nut and tighten it down enough to crush the washer and then about another 1/8 turn (you are not going to hurt it). I never had to used an air gun on one (should not be necessary to tighten it that much). I like to use a big 6 point socket and torque by hand so I can feel the washer crush.

Next, is the brake fitting and bolt that attaches to the big nut. Is this possibly the leak point?? Make sure your brass fitting is not craked and you are using another new copper washer between the fitting and the top of the big nut. Pilot Dan

vettefred

Just replaced mine....leaked until I cranked on the big bolt. That apparently seated the copper washers and the leak stopped.