Brake Fluid Leak at Bleeder Screw Seats after Rebuild - Now What?

[WingMan71]

Hello GS forum members,

Been a long time since my last post and my restored 1983 GL650GL now has a new home. (Should never have sold it!)

That said, I have a question that applies to most all vintage bikes.

I'm restoring a 1983 Honda GL650I Silver Wing. This was a one-owner bike with a 1984 title! Great find.

I just finished a complete disassembly and rebuild of both front brake calipers. Used Brakecrafters rebuild kits, which I've used in the past. Also installed new pistons, Galfer SS braided brake lines, and rebuilt the master cylinder as well.

Everything is fine EXCEPT: I have very small leaks at both bleeder screws! Arrrgggghhhh ! ! !

Figured this means the bleeder screw seats in the calipers must be bad. But, I inspected them during the rebuild and they looked fine. Not pitted or out of round, etc.

I first used the new bleeder screws that came with the rebuild kits. Since those leaked, I decided to get the old original bleeder screws and put them back in place in the calipers. Even the old ones still have slight leaks when closed.

Many decades of rebuilding vintage bike brake calipers and I've never had this happen before. What the heck?!

I sure don't want to waste these just-rebuilt calipers. So, what next?

Has anyone else had a bleeder screw seat leak in old calipers and, if so, how did you fix it?

Any advice would be appreciated.

[BEW]

That is very odd as I’ve rebuilt and sold over 50-75 calipers over the last 8 years and never had that happen. You could look up the bleeder part # used for that model/ year bike and buy a new set. The other suggestion would be to wrap the bleeder threads with Teflon tape screw/ seat it and see if that stops the leak.

[WingMan71]

That is very odd as I’ve rebuilt and sold over 50-75 calipers over the last 8 years and never had that happen. You could look up the bleeder part # used for that model/ year bike and buy a new set. The other suggestion would be to wrap the bleeder threads with Teflon tape screw/ seat it and see if that stops the leak.

Yes, it IS very odd. Never had it happen before.

Thought of the Teflon tape, but it's not the threads that are leaking, it's the seat at the tip of the bleeder screw. The tape may stop the leak at rest, but probably not with pressure in the system when the brake is applied.

[Dogma]

Both? I could see maybe one getting some kind of accidental contamination, but both? Like you said, it's not the threads that seal, but the tip of the screw. Metal on metal seal by deforming one until it conforms to the other. Perhaps something got in there that your eyeballs can't see?

[rphillips]

accidental contamination? yep, maybe, but again on both sides???

[salty_monk]

Teflon tape if you're sure it's coming from the threads.... I've seen this before with people using new bleeders on old calipers. Normally the OG ones don't leak.

[BEW]

^ so true salty- monk!