Brake Master Cyl vent or screw ?

[bayo500]

The brake m/cyl has a large screw on lid with a small screw in plug in the centre, should this have a fitting and vent hose instead of the plug, the reason i'm asking is after a test run i had fluid bubbling around the copper sealing ring on the lid and it's on pretty tight, do they normally leak or am i causing a pressure build up that should be vented? Thanks.

[Bob W]

A master cylinder cap needs to be vented. Normally a CJ-3A cap is vented with a baffle and a small hole. Sounds like you may have a cap from an M-38 where a vent line ran up to the air filter for underwater fording purposes.

[rocketeer]

Bob's right, it's probably an M-38 cap. However, you will need to vent it. You can try to find a CJ3A cap or you could replace the plug with a fitting and attach a tube that extends upward at least a foot or more.

Vernco did something similar to add a remote reservoir but it will give you the general idea:

http://www.vernco.com/brakes/id262.htm



Larry

[bayo500]

Thanks guys I'll sort it boxing day, happy Christmas...