Is my master cylinder done for?

[Christophe]

Hi all,

I was bleeding my front brakes today and noticed that brake fluid was leaking from my MC onto the ground. Luckily it did not fall on any other parts but just hit the ground. I checked it out and saw that the spring for the brake lever had punctured that rubber boot of the MC. I took a picture of the part I am talking about, but cannot get close enough to show the damage. Is this part replaceable or am I done for? I have seen rebuilds on Yoyodyneti but don't know if this particular part is replaceable.

Link to photo:
http://picasaweb.google.com/jeannelc/DucatiMasterCylinder



Thanks for the help,

Chirstophe

[Christophe]

Also let me know if the link to the photo works. I am not sure if it is set to public.

Thanks

[Speeddog]

It may just be a little brake fluid that's leaked past the seals, and now it's getting out through the rip.

But probably not.

[Speeddog]

Oh, yes, the pictures work.

These rebuild kits appear to have that boot:
http://www.yoyodyneti.com/Category.aspx?CategoryID=3016

Not sure which one you need, but give 'em a call.

[bigiain]

Is this part replaceable or am I done for? I have seen rebuilds on Yoyodyneti but don't know if this particular part is replaceable.

It definitely is on the coffin style masters (I did my clutch master a few years back with a kit from a Brembo dealer here in Sydney, cost me $26(AUD) from memory), but Brembo are a little bit weird about rebuild parts for some things, you can't get a seal kit for the rear caliper - Brembo say you've gotta buy a new one (I'm pretty sure Yoyo will sell you some seals that fit, but they wanted to charge me ~$20 for the seals plus $60USD for courier them over here so I bought a 2nd hand caliper for about that price instead...)

big

[Fresh Pants]

I just noticed my clutch master is in almost the same state, not leaking (yet), but the boot is definitely ripped.
It's never really felt quite right, but as it was my first bike, I figured it being one of those Ducati things. Hmmm.
Probably time to take it apart and figure out what's going on.

[Howie]

I can't see well enough in the photo, but if there is brake fluid in that boot you have a leak, but when they manufacture the part they do use silicone grease in the boot.  When you check out YoYodyne for the kit also check out the price for a brand new replacement.  Do speak to Fred before ordering.

[mangeldbug]

So Yoyodyno has caliper piston seals and master cylinder rebuild kits??  I have an '02 M750S.  The local Ducati dealer said Brembo doesnt offer either.

I dont think its a fluid leak in my rear caliper, my pistons on the one side are really tight and the pads are dragging.  Cleaned it VERY thoroughly and that helped a little, but still dragging.  Im going to replace the caliper pin and spring to see if that frees up pad movement.

Front master cylinder may have a tiny leak behind the boot - its been looking a little grimy at my lever pivot point.  I saw it a while ago, but assumed it was just road ick since I ride in the rain.  Lately though the front brake has been really mushy, like its pulling air from somewhere.  I bleed it, get a little air out, feels great, but then the slop in the fr. brake lever is back in a week or so.  Ive cracked the bleeder, zip tied the lever to the bar and left it overnight and it feels awesome after that, but a week later the slop is back.  Frustrating.  I really dont want to buy all new calipers &/or master cylinders.

[Howie]

I would call Fred at Yoyodyne direct and ask about availability  973 386 0040   Seal kits are quickly vanishing.  The good news is Fred sells new coffin cylinders and rear masters at a very reasonable price.

[mangeldbug]

Argh...  Well if it is my MC and/or calipers, there are no parts or rebuild kits available for the '02 750. 

Fred was busy, but he said I could call back to maybe help me diagnose what the most likely problem is.  I dont want to replace everything when the issue is only with one or neither of the things I am suspecting.

I just want to know what the heck happened to make my brakes go kaplooie!  I only have 12000 miles on the bike...

It did sit for 4 years prior to my buying it, and I immediately switched out the brake fluid for regular DOT4 (@ 2000 miles).  I just recently switched out the brake fluid for 5.1.  Since it is lower viscosity, could adding that have cleaned out the gunk that had built up from sitting before and now its got a leak?   

[mangeldbug]

Fred is an awesome guy.
He could have easily said "its probably your _____, new one costs $____ from me" but he took the time to troubleshoot my issues.

Here is what I learned!

Brake cleaner = bad

Brake cleaner will suck out the brake fluid in the gap where the piston fits in the caliper and will dry out the seal not allowing it to retract properly (like in my rear, brakes dragging) or hyper-retract causing slop (like in my front).

He said air feels different than what I am describing. Air feels mushy the entire way, but I just have more lever travel until the brakes engage in front - then they are nice, strong, and predictable as usual. I told him we tied the lever to the bar which helped making us suspect air, but he said that works because it allows the stuck piston(s) to get back up to the pad and the piston seal can slip back to where it is supposed to be. Feel is good temporarily, exactly like I experienced.

He said to verify, press on the lever/pedal and see if any piston(s) lag behind the rest or get sucked into the caliper. To fix it, put a few drops of brake fluid in the gap around the piston and work it in pushing the piston in and pumping it out a few times to relubricate the seal. For the rear, check the brake pedal and rod position to see if there is any load on the brake when it is not engaged.

He said there is nothing wrong with using 5.1 brake fluid.
If I dont have to buy any expensive Brembo parts to solve this problem, that would be cool.