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Master Cylinder Seal Question

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J

jjscott

Senior Member
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I am rebuilding the drum brake dual master cylinder with the Moss kit (180-970). The main seals and washers fit the bores correctly. The secondary seal is to be stretched over the piston and then slid into the bore.

The pictures show the seal over the piston; I believe it is properly seated. The diameter is a good 1/32" greater than the bore. Do I just force it into the bore? I am afraid it will be so tight the spring won't return the piston. Have I done something wrong?

Jim
 

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Jim, i believe you have the seal on backward's. If you fit it the other ways around and lube it with a little brake fluid I don't believe you will have any problem's.

Kurt.
 
Problem Solved:

I pulled the seal back toward the center. Pulling it back revealed that the lip on the rear side had been rolled under and preventing the seal from fully seating in the groove in the piston. It wasn't on backwards, it was just on wrong. Thanks, Kurt, your post made me move the seal and disclose the real problem.

Picture correctly installed.

Jim
 

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That looks right, Jim. Should work fine now.

Kurt.
 
And it should be a bit of a snug fit in the bore, remember its pushing against the fluid and keeping it from running out the pushrod end of the master. Too loose and you get leaks.
 
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