Master cyl venting question

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Jun 12, 2007 | 10:25 AM

brider

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From: Orange, CT

Master cyl venting question

It occurred to me as I was about to replace the M/C on my '66, that there is NO vent at all in the top screw-cap, unlike more modern M/C caps that are vented.

So how does the brake system allow for pad wear or excessive pedal travel (brakes out of adjustment) without causing a vacuum in the M/C itself?

Jun 12, 2007 | 10:45 AM

norvillebob

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From: mountaintop, Pa

The rubber boot just collapses under the lid.???

bob

Jun 12, 2007 | 01:00 PM

brider

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From: Orange, CT

Never thought of that, does the big screw-on cap on my '66 HAVE a rubber boot? Then the boot would have to be vented, also, and I just don't see a vent...

Jun 12, 2007 | 01:05 PM

norvillebob

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From: mountaintop, Pa

HMM ya know what I was thinking dual chambered. That was the first mod I did from a 68 with Drum/drum.

bob

Jun 12, 2007 | 02:24 PM

NumberDummy

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From: Simi Valley, CA

What "modern" master cylinder cap is vented?

Jun 12, 2007 | 02:56 PM

airharley

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From: Escondido, CA

Bill they are refering to the air gap that exists between the rubber gasket and the cover assembly.

For the single master cylinders there is only a pin hole near or under the retaining clip or for screw ons almost dead center of the cap. Dual masters have what looks like a pinch mark in the metal cap over each side of the reservoirs.

Jun 13, 2007 | 07:07 AM

brider

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From: Orange, CT

The reason I focused on the "venting" is because I have an older non-Ford truck with dual-chambered master cyl, and the (2) separate chambers have obvious vent holes in the caps. Makes obvious sense; if the fluid level changes (whether by actuation or pad wear), AIR has to take up the space, or a vacuum will occur.So the old screw-on cap IS vented? Good enough for me.