Part: Master Cylinder CAP

[jimgnj]

Strange thing I noticed: Brake fluid on the top of the Master Cylinder cap. I looked and sure enough saw a pin hole sized air bubble. Anyone have cap for sale or know where to get one? Thanks.

Jim

[Matt Cashion]

Unless I'm mistaken there is brake system pressure under the cap when the brakes are applied. I don't think solder or JB Weld would be a proper repair.
If there is one pin hole how long before another shows up. I think a new cap, or good used cap, would be the proper repair.

[jdsnoddy]

Unless I'm mistaken there is brake system pressure under the cap when the brakes are applied. I don't think solder or JB Weld would be a proper repair.
If there is one pin hole how long before another shows up. I think a new cap, or good used cap, would be the proper repair.

Good comment. Perhaps the ultimate solution would be to get a new duel reservoir master cylinder. Brakes are a vital safety feature with no room for error. Thanks Matt. John
P.S. I think White Post Restorations could hook Jim up with whichever solution he chooses. Jds

[jimgnj]

I found a good used cap...I think. The emergency brake is working correctly!!! (ha ha intended). I probably will eventually go with a modern dual master, but I just got it so I'm sorting things out. I did actually adjust the e brake after lubing the system. Brakes, they are NOT overrated!

[lld]

Most brake system reservoirs are vented, either through the cap or somewhere else, so that atmospheric pressure can act on the fluid in the reservoir and a vacuum does not develop as fluid is drawn from the reservoir into the master cylinder cavity. Therefore, a small hole in the top of the cap would normally not be an issue unless the reservoir is overfilled. I would expect the real fluid level would be at least 1-1.5" below the top of the cap.

Unfortunately, my car is away having a grille hockey stick bring ground, polished, and rechromed for a better fit so I can't look to see if the cap itself is vented and the height of the cap versus the reservoir level..

Larry

[Roger Zimmermann]

The cap is vented, otherwise the system would not function properly. If brake fluid is coming out at the cap, the compensating valve may be no more tight: it closes the fluid path between the reservoir and the hydraulic cylinder during a brake application.

[jimgnj]

The cap is vented by a pin hole? Makes sense. I did fill it to the top when I got it. Perhaps I made a mistake, it's possible. I was due to make one! Thanks for help.

[Roger Zimmermann]

Exactly, a pin hole. The master brake cylinder is like a radiator: don't fill it up to the top!

[jimgnj]

Thanks,I now a spare cap with.... a pinhole vent!!! Live and learn.