Topic: Weird Master Cylinder Fluid Weep - 500 Four

[paulbaker1954]

I seem to have a small amount of brake fluid appearing under the rubber boot around the end of the master cylinder.

I have replaced both banjo washers with new copper ones and replaced the bolt. There is no fluid on the hose or around the hose end so I think its not coming from the hose.

If I wipe it all clean and leave for a day or so I find fluid around the inside of the top of the rubber boot again.

If you squeeze brake lever I cant see any obvious leakage and brakes are working a treat and are firm.

Given that fluid can't climb up from the joint into the boot this is now mystifying me

Anyone got any bright ideas.

[pjlogue]

 If the banjo fittings are not leaking there are two possibilities.  1) if the break lever was pressed too far and the plunger went past the opening in the bottom of the reservoir the fluid can get behind the plunger where it will weep out by the lever.  Or 2) the plunger rubber is deteriorated or the MC bore is corroded and allows fluid to get past the plunger.  The fluid will weep from beneath the end rubber seal at the end of the plunger.

-P.

[Bodi]

This is the brake line end, correct? With nothing under the boot except the butt end of the MC and the brake line banjo/washers/bolt?
Very very odd. Could the MC casting be porous or cracked? Or the banjo fitting? Is the a tiny leak from the hose/banjo joint?
Try leaving the boot off overnight with the MC compressed - wrap a bungie around the lever and bar? That might show you where the ooze is coming from.

[jonda500]

Did you try tightening the banjo bolt just a tad more? - that's what I had to do, but I didn't use new washers...
John 

[754]

Two things that may matter, be sure the end of mc is clean, may mean running a file across it, and examine for evidence of something that dug into the surface.
Same think with bolt head, if its not machined where it sits against crush washer, it may not be bearing down evenly..dont think the OEM ones have this problem.

[Scott S]

 I had some cheap copper washers from Harbor Freight or somewhere that must not have been annealed correctly. They leaked no matter what I did. Replaced them with proper brake line washers from the auto parts store and that cured it.