Thread: Odds and Ends
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Old 11-17-2013, 01:35 AM
BillGrissom BillGrissom is offline
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Join Date: Aug 2010
Location: Sacramento, CA
Posts: 2,748
I used a regular round cross-section O-ring (from a Harbor Freight kit) with a rebuilt MC because the square one that came with it seemed a bit too thin to seal well.

It seems many 1990+ cars have a vacuum seal between the MC and booster. That allows the booster to be much thinner. In 60's U.S. cars, there is an inner bellows around the brake rod to make the seal. The disadvantage of the design in our cars is that a leak past the MC cylinder sucks brake fluid inside the booster, rather than just running down the firewall. I use DOT 5, so less concern with what the fluid will do.
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