Mud for brake fluid?

[Guest]

Popped open my master cylinder to see what needs to be replaced. From the looks of the outside I didn't think it had any fluid in it. The outside is flacking and there is a gap at the bottom of the reservoir. I assumed it would hold liquid. I was surprised in three ways after opening it. First, it didn't leak, two it looks like it is full of mud and three pulling the lever still worked and would compress the pads.

What to do, what to do...

Obviously it needs to be cleaned and new gasket. Can this system be salvaged?

[tkent02]

Yes, disassemble and clean the master cylinder, both calipers, replace the lines. The "Mud" is brake fluid, water and rust particles caused by running old fluid forever, the water in the fluid builds up and rusts any steel things. The problem is that particles of rust can and will block the return port in the MC, and lock the wheel when you least expect it. Both front and rear brakes will be in similar condition, do them both. Yours are not so bad, the next phase is when the brake fluid turns to brown sugar, at that point it's a lot harder to clean everything out.

[Mop Bucket]

Thanks. New question, is new brake fluid the best thing to clean the parts with or can I use brake cleaner or something similar. I am worried about the rubber parts and plastic parts.

[almarconi]

Use clean brake fluid to clean everything.

[hikermikem]

I completely disassemble the calipers & master cylinders, then simply scrub everything clean in a bucket of warm soapy water... blow dry after wards.

I use an old toothbrush & q-tips to get it all clean. inspect all the parts & seals afterwards & determine if you need to replace anything. The OEM rebuild kits (caliper & MC) are the best value IMO if needed. You may be surprised to see how well the components clean up though...

the hard part is getting that circlip out, that holds the plunger in the MC.

[cowboyup3371]

the hard part is getting that circlip out, that holds the plunger in the MC.

He's right. I had to use my woodworking vise in the garage to hold it while I managed to get it out. Took a few minutes as you have to hold the plunger down at the same time with your other hand.

[Planecrazy]

The hard part is getting that circlip out, that holds the plunger in the MC.

He's right. I had to use my woodworking vise in the garage to hold it while I managed to get it out. Took a few minutes as you have to hold the plunger down at the same time with your other hand.

I haven't done this myself, but my first thought after reading these comments is: Why not use a small plastic clamp to hold the plunger down, so that both hands remain free to work off the circlip?

Regards,

[bobthebiker88]

trust me, I've TRIED holding the piston down with something while removin the circlip. doesnt work. whatever you use to hold it, gets in the path of your tools, and makes removal ALL but impossible. or mighty close.

[cowboyup3371]

You have to basically push it all the way into the cylinder hole and none of my clamps were small to do so.

[Planecrazy]

trust me, I've TRIED holding the piston down with something while removin the circlip. doesnt work. whatever you use to hold it, gets in the path of your tools, and makes removal ALL but impossible. or mighty close.

You have to basically push it all the way into the cylinder hole and none of my clamps were small to do so.

I HATE when that happens!

Regards,

[tkent02]

Long needle nose pliers, file the tips round, you are golden.

[Nessism]

I agree with Mike about using hot soapy water to clean the parts. After everything is clean you need to closely inspect the bore inside the master and on the caliper pistons; if there are any pits in the metal the parts are junk and must be replaced. Considering the condition of that brake fluid, I'll give you less than a 50% chance the parts are not corroded.

[jhicok]

sounds just like my headache i dealt with.. i bent a microtip flat screw driver to 90 degrees and hooked one of the eyelets. the circlip was all bent when it came out but it came out. the oem piston cup set from bikebandit.com came with a new one anyways. to get the new circlip back in i got both the eyelets back into the groove using two non-bent microtip flat screwdrivers. ( this is a pain!! ) once both the eyelets were in the groove i flipped a 12mm deepwell socket over the piston and gave it a light firm hit and bam!! the clip popped right in.

[jhicok]

also the piston cup set came with all new rubber pieces and i used brake fluid to clean everything. i also let it soak in acetone for a night to get off the gobs of crappy paint work done by the po.. it turned out good. dont forget to order a new diaphram to while you got it apart anyways

[sschering]

The original Front MC on my 78 GS750 was locked up solid..
Just for giggles I tore it down and tossed the body into the carb dip can..

I ignored it for a week then fished it out.. The piston had loosened up and could now be removed without damaging the bore..

Around my shop if it's metal and dirty it ends up taking a trip through the carb dip..
Burnt on oil, varnish, paint.. it all comes off..