Correct removal of master brake cylinder reservoir

Orig65Tiger

Bronze forum user
Messages
25
As part of a brake system rebuild, I need to removed the fluid reservoir on my master brake cylinder. The reservoir is the type that attaches directly to the top of the master cylinder. It is not the remote version.

I don't want to destroy any seals/washers that may be impossible to replace. Do I simply loosen the nut accessible from inside the reservoir and and then lift off the entire unit? (I haven't done this since the nut is surprisingly tight.) Then do I loosen the base piece that is threaded into the body of the master cylinder to remove it? Are the seals/washers that I need for reassembly readily available hardware or auto store items or something special?

Also, the rubber washer inside the top of the cap needs replacing. I know I can get a replacement moisture barrier for inside the cap, but is the washer not replaceable with an O ring or rubber washer of the correct size?

I appreciate the help, Jim
 

Orig65Tiger

Bronze forum user
Messages
25
Since I couldn't come up with any advice from this forum or outside, I went carefully ahead in the removal of my fluid reservoir. This little project leads to having my brake master cylinder sleeved.

I mounted the master cylinder in a vise with protected jaws. The nut inside the fluid bowl was very tight. With the nut removed, the washer beneath the nut and the bowl lift straight up. The nut is tightened to a shoulder cast into the top of the threaded fitting that feeds brake fluid from the reservoir into the master cylinder. The sealing washer under the bowl was undamaged. I think it could be replaced with a hardware store O ring or washer if need be.

The threaded brake fluid fitting can now be removed. The retaining nut was also very tight. One side of the nut is partially recessed into the body of the master cylinder. You need a perfect fit with a socket or wrench to make sure you get a good grip on all sides of the nut. I wasn't sure if this needed to be removed before sleeving the master cylinder so I sent the cylinder to the shop with the fitting attached. I'm not a big fan of taking apart more than necessary especially when it's tight and can be damaged.

I still don't know the answer my last question about the moisture barrier inside the cap. In my case, the large rubber washer inside the cap is worn but not torn. I can't tell how the center section in the cap works. Does anybody know how to test if the moisture barrier is good or bad?

Jim
 

o2bdriving

Gold forum user
CAT Member
Messages
166
Poking around, I found this posting. I just noticed that the reservoir was a bit loose. Drained the fluid from the reservoir and noticed that the fluid had a grey tint. Upon removing the reservoir nut, washer and bowl it appears that pipe dope was put on the male threads of adapter that extends into the master cylinder main body. There was a rubber seal under the bowl Hoping that is correct as I'll likely do the same when reassembling.
 
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