'65 Master Cylinder Cap & Seal Assembly

[Jim B.]

Hello
My '65 standard brake car has had a persistent brake fluid leak at the master cylinder for a couple of months now. I am pretty certain it is leaking across the cap/seal and down the side of the cylinder. I have been studying the cap and the seal assembly and I am now wondering if the two were assembled incorrectly by the previous owner of the car. In the attached photo, the seal is shown in the cap as I removed it from the cylinder. In the second photo the flip side of the seal is shown. Which way is the seal supposed to be mounted in the cap? As the cap is fabricated to rise up above the top of the master cylinder about .5", shouldn't the seal be installed such that it projects up into the cap rather than project down into the reservoir? As installed when removed from the cylinder, the seal was mounted in the cap such that it projected down. If that is the correct orientation for the seal, why is there such a large empty volume above the seal in the cap?

Hoping someone can explain how this arrangement is supposed to work.

Thanks in advance

[Joe L.]

Re: '65 Master Cylinder Cap & Seal Assembly

Hello
My '65 standard brake car has had a persistent brake fluid leak at the master cylinder for a couple of months now. I am pretty certain it is leaking across the cap/seal and down the side of the cylinder. I have been studying the cap and the seal assembly and I am now wondering if the two were assembled incorrectly by the previous owner of the car. In the attached photo, the seal is shown in the cap as I removed it from the cylinder. In the second photo the flip side of the seal is shown. Which way is the seal supposed to be mounted in the cap? As the cap is fabricated to rise up above the top of the master cylinder about .5", shouldn't the seal be installed such that it projects up into the cap rather than project down into the reservoir? As installed when removed from the cylinder, the seal was mounted in the cap such that it projected down. If that is the correct orientation for the seal, why is there such a large empty volume above the seal in the cap?

Hoping someone can explain how this arrangement is supposed to work.

Thanks in advance

Jim------


It's easy to determine which is the correct orientation of the seal. The seal should be installed so that the center portion (the bellows) can expand down into the resevoir. It is designed to do this so as to take up the space of the brake fluid as its level drops due to wear on the brake pads. There should be only one orientation in which the bellows will expand into the resevoir. My vague recollection is that the correct orientation is as shown in your second photo, but I'm not 100% sure. Simply depress the bellows to see which way it extends and you'll have your answer.