Topic: 65-66 Non-Power Brakes MC Cap Gasket Question

[RRod]

Which way does the larger Bendix Master Cylinder cap rubber gasket with bellows normally install on 65-65 front disc brake Mustangs?

Does the unexpanded bellows portion fit up into the domed cap area with the flat portion down onto the MC rim?  It looks like the cap dome was designed to fit this 3/8" worth of unexpanded bellows perfectly.  Or, does the 3/8" worth of unexpanded bellows drop into the MC, which if filled to the normal 1/4" from the top, will spill over during installation as the unextended rubber portion of the bellows displaces the brake fluild as it is lowered onto the rim?

There has been quite a bit of controversy over at the Corvette Forum as to which way is correct (the 65-66 non-power brake Corvettes used essentially a nearly identical Bendix MC).

http://forums.corvetteforum.com/c1-and-c2-corvettes/2812741-65-66-non-power-brakes-mc-gasket-cap.html

Personally, I don't think it matters as the bellows expands in both directions, however, the design of the domed cap seems to be giving us a clue the the flat side of an unextended rubber bellows gasket was intended to face down.

Thanks.

[J_Speegle]

Depends on the version - after the "fix" I believe there are ribs along the bottom (meeting the top lip of the master cylinder. Can't remember if the earlier version has them also.

The bellows are designed to move downward as the fluid is reduced - as you mentioned they will travel in either direction if it were needed.. Seen this take place on many of the dual style ones.  Believe for the seal at rest the "dome" was designed to fit up into the cap and not contact the fluid

Believe the TSB article  have a number of diagrams that show the differences between the early and late seal and installation 

[RRod]

Thank you Jeff ...... A similar opinion to your's was also reached just this morning over at the link for the Corvette Forum.

BTW, I'm not familiar with the "fix" issue you referenced ..... Could you kindly point me to a link or info so I can be sure to get the correct version of gasket, i.e. is it about there being outer edge concentric sealing ribs on both sides of the gasket rather than just on the top side?