Leaky Master Cylinder

[GLRnTX]

I went to ride my truck a few weeks ago and found very quickly I had no brakes. I checked the Master cylinder and found it empty. I did not see a drop of brake fluid on the garage floor, but I discovered a slow leak on the output side of the MC.

My question: Is OK to use RTV to provide additional sealing to the crush washer that is usually used? or would an O-ring work better?

I bought a 18" long 1 7/8" wrench to tighten the screw cap to the MC and it just keeps leaking. You can see a drop in the photo.

The one shown installed is a brand new MC. I tried to rebuild the original and could not get it to stop leaking. I figured it was too badly scored. The cap and ring photo are the original parts.

Greg

 

[vwnate1]

Leaky Flange

My old '46 3100 did this too and sorely vexed me .

In time , I got a 6 point socket and long breaker bar and had at it ~ I figured since it leaked anyways , no hard if I stripped or cracked the M/C .

NO you MUST NOT use RTV on the plug to seal it ! .

Maybe a new crush washer is in order here ? solid copper ones seem to seal the best IMO .

 

[GLRnTX]

Unfortunately, the new crush washer is copper and does not seem to help.

 

[vwnate1]

Leaks

Hm ;

Maybe an aluminum one ? .

Your picture doesn't show any rusting/pitting on the open end of the cylinder bore , maybe you could lap it a bit ? .