Weeping Brake Caliper - 1985 R80RT

[QuixotesHorse]

Hi Everyone,

I'm having a problem where the bottom on some of the bleed screws (2 of 4) on my brake calipers are damp (1985 R80RT). It might be a bit hard to see but there is shininess on the cap's ring.

It's not a major leak; I've left the bike with the brake lever tied down for several days to observe but there are no drips, just dampness at the base of the screws. I'm looking for suggestions to rectify the situation. I've tried re-torquing, removing the screws and cleaning the mating surfaces best I can, and buying new bleeder screws but the dampness persists.
I've been thinking about taking one the bleed screws and filing off the threads (blue region in my poorly made diagram), then applying grinding paste to the bottom mating surface (red region) and gently rotating the smoothed screw inside the caliper to recondition surfaces akin to how we do valve lapping. Let me know if that sounds like a bad idea.

Thanks in advance!

 

[zer0netgain]

I was going to suggest a gasket, but my understanding of bleeder screws is that a gasket wouldn’t be thick enough to work. If it’s a standard sized bleeder screw, try replacing it and see if the replacement has the same issue?

 

[olironrider]

… piston seals seeping and brake fluid migrating ?

 

[QuixotesHorse]

I was going to suggest a gasket, but my understanding of bleeder screws is that a gasket wouldn’t be thick enough to work. If it’s a standard sized bleeder screw, try replacing it and see if the replacement has the same issue?

Are you suggesting a gasket at the bottom of the screw? I've seen copper "cone" seals before. I think those are usually for fittings but I might have to see if there are any that happen to match the size and angle of the bleeder screw.

… piston seals seeping and brake fluid migrating ?

I don't think so my calipers sit at 12 o'clock relative to the wheel with the bleed screws on top so piston seal leaks would leak down and away from the screws. Plus I replaced the seals since I had the calipers apart anyway.

 

[ccolwell]

It's a long shot but a dab of grease on the threads might be enough to seal it for a spell. If you put a lot of miles on it< I don't think that will last long.

 

[melville]

It's a long shot but a dab of grease on the threads might be enough to seal it for a spell. If you put a lot of miles on it< I don't think that will last long.

I've put Teflon tape on bleeder screw threads, mostly to facilitate either reverse or vacuum bleeding. That may help here.

 

[AntonLargiader]

Does not sound like a bad idea to me, but I'd have a really good look first to see if there are any blemishes in that surface.

 

[stevenrankin]

Make sure the teflon tape if used doesn't block the bleeder hole or you will have fun next time you bleed the calipers. St.