I'm rebuilding a master cylinder and all is going well enough except I'm not sure what the valve here is for or which way it is supposed to be assembled. If I knew what it was for I might be able to decide what to do with it! The pic is of a Kawasaki 50z loading shovel brake tandem master cylinder. I've laid out the bits of the valve leading to the rear brake line. Right now I'm thinking of inserting the spring, then the black cap with rubber side facing out then the retaining nut containing a valve assembly for the rear brake line. The black cap is a valve assembly according to the parts manual, i just don't know what the valve is for. There is another valve like this for the front brake line, I've it laid out beside it... minus a spring.. here somewhere.. Any thoughts?
Don't know exactly how they go in that particular master cylinder but I believe they are a residual pressure check valves, they hold fluid in the lines so your pedal will be firm near the beginning of the stroke instead of way down. You may or may not be missing a couple parts. Here's a picture of a similar master cylinder:
Ah yes that makes sense. I'm missing no. 18 on you're diagram, maybe it's no. 36 on mine which is down as an "element", I don't have it anyway. Hopefully it might work without it, I doubt it was installed before I got it and the brakes worked then. Have you ever seen a tipping valve and inlet cap like below? I can't seem to find them anywhere and am just hoping the rubber will seal ok.. after 30 years lol It looks like a moulded seal on it and I can't get it anyway. I originally wanted to replace all the springs and seals but I'll have to settle for most of the seals instead. I'm assuming that the seal on the tipping valve is super important to build up pressure to work the brakes. The flat part of the silver valve on the right seals on the inner ring of rubber on the cap. Maybe I could remove the old seal and use some rubber grease on it and reinsert it to get it more evenly seated or something if I can't get a new one.
No, haven't seen that before. Doesn't look terrible to me, I think if it was bypassing you might see more damage than that but I am no expert. If you find you absolutely have to replace that seal an o-ring for the outside and a quad ring with some gel super glue on the inner one? Brake fluid might dissolve the glue though. What was the original problem, leaking down or?
There should be a glue somewhere that resists Dot 4, and the quad ring might work then... I'll see how it goes when all is re-installed and freed up. The brakes stopped working years ago, I think that they could build up pressure for a while with a lot of pumping but not too sure. There was a lot of oil around the master cylinder, fairly messy. When I took it apart last week the pistons were stuck, almost seized. I've freed up and smoothed everything and put new seals on the pistons. The old ones were fat and soft. When all reassembled I blew air through the rear brakes outlet and could hear a faint whistle of air through the tipping valve. Swapping the cap moved the noise to the front brakes. I'm hoping the Dot 4 seals better than air, not too hopeful tho.. The cylinder is back in and now I'm looking at opening up the corroded/stumps of bleed valves, disconnecting the lines from the calipers and freeing up the calipers.
Are you sure it is supposed to be DOT 4? I know nothing about Kawasaki, but if it's supposed be something else, like hydraulic oil, that'll cause fat and soft o-rings, and other problems.
Or vice versa as it has a hydraulic booster the master cylinder bolts to. If the booster leaks and the vent port is plugged you fill the master cyl with hydraulic oil. Or if somebody mixes fluids unknowingly.
Dot 4 is what it always got back when it worked and is what was in the bottles when I opened it up. I'd thought about it alright, just glad it wasn't mineral oil, can be a pain to get seals for that stuff.
There was oil in the plunger area but I think it was brake fluid, I never ran the engine with to check for leaks from the booster. Here's hoping! As for super glue with a seal and Dot 4, it seems that is a non runner, Dot 4 is just too good at reacting with stuff.