Help with Master cylinder seals any help please

[dsan1964_imp]

What’s happening fellow CBer’s. I had the great idea to re-cycle take out old and add new,clutch fluid and brake fluid , and I put the tops back on and it seems that I keep getting a little leak or blow back mist of fluid. I have thoroughly cleaned and they are not over full I’m thinking about getting new gasket does anybody know any tricks or ran into this thanks.


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[Lord Popgun]

On the advice of my dealer’s service manager (old time Honda mech) I change mine every time I do fluid service. He said leaks are common on re-use. They are not really expensive and mine get changed every 2 years when I change the fluid (clutch and brake).

[max]

Having just worked quite a bit on my brakes and found that i only fill to half of the sightglass, i think the small amount of air below the black "bellow"seal on top of the fluid can only contain a small amount of moisture, not enough to cause a problem and need to be dried and wiped especially on the seam area to stop fluid seeping out of the lower part of the lid when mounted back in place and attacking the painted area, i also apply some grease under the lid and the screw threads to slow corrosion in those area's and provide more protection for the exposed aluminium.

The scews need to be only tight enough, if done up more they start to deform the aluminium lids, that can be checked by placing the lid on the body without the seal and white breathing plate, tightening the screws and check for a small gap between the lid and the body, maybe with feeler gauges, a piece of paper or similar.

As you have noticed before no leaks should happen in the seal area and no sealant should be used in the process, the fluid is meant to stay under the black seal and no moisture should be on top of it, the white plastic spacer has a tiny hole in the middle to let air pressure equalize as the fluid level gets lower and the pads wear down over time using some fluid from the reservoir.

Just wondering if you have also replaced the old fluid inside the slave cylinders by cleaning the dust on the pistons from the outside and then pushing the pistons back into the housing, taking the old fluid out and bleeding the line until the fresh fluid comes out after which the pistons can be released to come to their working position behind the brake pads.

A bit long winded and you may just go with popgun's advice.

Maybe some more advice is coming your way, in the meantime all the best!

[Lord Popgun]

Max makes a good point about the screw tightness. The torque spec on the screws is only 1.1 ft lb. So don’t crank them down!

[peterbaron]

What’s happening fellow CBer’s. I had the great idea to re-cycle take out old and add new,clutch fluid and brake fluid , and I put the tops back on and it seems that I keep getting a little leak or blow back mist of fluid. I have thoroughly cleaned and they are not over full I’m thinking about getting new gasket does anybody know any tricks or ran into this thanks.


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There are no tricks, but proper diagnosis..is your lever/pedal soft, spongy or you have leaking fluid...or something else, specify, please.
Cover gasket has nothing to do with pressure.
It is very rare that after flushing brake/clutch fluids your seals/o-rings failed and are not holding proper pressure..
If bleeder was not tight enough follow Max & Popgun advice

[dsan1964_imp]

Max makes a good point about the screw tightness. The torque spec on the screws is only 1.1 ft lb. So don’t crank them down!

Yes, that would seam to be the problem to tight! Took a bit of fluid out and snugged screws down


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[max]

dsan thanks for the feedback, we appreciate it and most importandly the readers find out what works and what doesn't.

It is actually very importand to let the group know what the end result is and close the loop, results good or bad are more importand than the actual question and also provides the opportunity to elaborate and keep looking for the right solution.

Sometimes we don't get to know what the end result is and nobody is the wiser......

So thanks very much for the feedback and thanks popgun for pointing out the bit that fixed it.

[Cormanus]

Good point, Max.

Just for clarity, was the solution, not tightening the screws too much, reducing the quantity of fluid in the cylinder, or a combination of both?

[max]

Hi cormanus, i could not decipher the attached pics and i think the clue was in there but i think the screws were the deciding factor, a new seal is bigger and softer in this area and if the black bellows are not in the same position or swapped i guess that could make a difference, and if they are tight enough the middle of the lid will bend enough to allow for some fluid to get out.

I left my fluid level where i can see it, so there is no case of " is it empty or full? " when i look at the sightglass, different story with a factory fill where they fill to account for use in the slave cylinders over time, so they get filled more.

[Cormanus]

Max, thanks for the clarification.

I don't think there were any pictures in dsan's second post. Just Apple emojis that don't always translate in the Forum software.