Topic: HELP! Newbie needs help with Master Cylinder leak

[johnl]

Hi everyone,

Well I've been immersing myself in the forums here lately, and it really has been pretty danged inspirational, to the point that I'm now feeling brave enough/motivated enough to tackle something myself.  I recently had installed a nice condition, rebuilt master cylinder assembly.  I had it bled today so that it had good pressure at the lever, but I don't wonder if something went wrong when it was being bled.  I now have a fluid leak where the lever pushes/contacts the cylinder piston (?), which I can only assume pushes the fluid through the line.  I looked at the exploded view on one of the sites that show the parts fiches, but unfortunately that part isn't described on any of the sites I looked at (no longer available apparently).  The exploded view shows it as #33 I believe.  Also, I did some research in the forums, and I'm wondering if what follows is what happened (I copied the following from one of the forums I found when searching -- see the warning in ALL CAPS):

"Another way is to bleed the m/cyl itself first.

Fill with fluid & then pull the lever in slowly & gradually

When an air bubble pops from the hole in the bottom of the reservoir STOP, let sit for 30 seconds & pull lever in again

You'll get three or four air bubbles each time

DON'T PULL THE LEVER IN ALL THE WAY or you'll have to pull the cylinder apart to reseat the piston seal

This method takes about 20 minutes  ('till theres no air bubbles) & then you bleed as normal from the caliper(s)

I've used this for eons on bikes/trucks/cars etc etc"



Is it possible my piston seal came UNSEATED?  The fluid has leaked enough now to the point that it's way below the fill line inside the master cylinder.  Also, the guy who bled it today filled the system with some sort of DOT 4 racing fluid, so hopefully that has nothing to do with the leak.  I appreciate all suggestions/remedies, but please keep in mind I'm a novice.  If you tell me I'm going to have to take something apart, you'll have to be pretty detailed.  Thanks so much for your suggestions, I look forward to hearing them. 

"It would be a cold, dark world without beer."  -- Anonymous

[johnl]

Hi again everyone,

I originally posted this pretty late on Friday night, so I can only assume that's the reason for no response from the experts around here.  Just to quickly recap, is it possible my piston seal came unseated (SEE ABOVE)?   I'm pretty sure the lever DID get pulled in all the way (I didn't do it myself) when the brake was being bled.  It was bled with one of those vacuum bleeder devices.  Really I'd just like to know if the seal came unseated so I know what I'm up against -- or if the 'nice' rebuilt master cyl. I bought is possibly too worn out to rebuild.  Like I said above, it sure does LOOK nice like it came off a good bike, but then again one has to wonder why it came off the other bike in the first place.  Someone HELP!

[750goes]

sorry you had no reply,

you possibly need to rebuild the master cylinder if there is fluid leaking from the lever end ......

[Gordon]

Who rebuilt the master cylinder that you installed?  Sounds to me like it either wasn't rebuilt at all or rebuilt poorly. 

[Bob Wessner]

I have no idea if this is your problem as I'm sure nobody else would do something like I did my first time. I stripped, cleaned and rebuilt the M/C and caliper, then filled and successfully bled the system. Felt real proud of myself. Next morning went out to the garage and found some brake fluid on the garage floor directly below the lever end. Hmm? I found out that the seal is supposed to mounted ON the piston, not in front of it, like I had done. This was pointed out to me after posting a pic of my handiwork. After, unfortunately, having to disassemble the M/C and do it correctly, it worked and still works fine three years later.. imagine that. I hadn't interpreted the bracket on the parts diagram correctly. Just thought I would mention it as a possibility, however remote.

[johnl]

Hi Every one,

Thanks for all the replies.   The M/C was rebuilt by someone at Western Hills Honda, who I'm sure a lot of you are familiar with.   They just rebuilt it last week before they shipped it to me.  Thing is, it wasn't leaking when originally filled with fluid, but the guy who installed it couldn't get any resistance at the lever.  I assumed it still had air in it, and I had it vacuum bled, and after that there was nice resistance at the lever.  But shortly after getting it home and taking it for a ride, I noticed fluid dripping out onto the garage floor.  So, if it wasn't leaking at first before the air was out of the system is that possibly just because there was no pressure at the lever?  Or, I'm still wondering, is it possible for the piston seal to come unseated as in my first reply above? 

RE:  Bob Wessner's post, I'll take a good photo of what it looks like in there so maybe someone can tell me if it looks like the seal is mounted on the piston like it should be.  Again, thanks for all the replies.  I really want to get this resolved because it's really the only issue the bike has now (that I know of!).  Cheers.

[Bob Wessner]

I do find it hard to believe someone at Westernhills would do what I did. Pictures might help somehow though.

[johnl]

Here's a photo I just took -- I hope no one was expecting to see all the parts out of the M/C!

[Bob Wessner]

Sadly, it doesn't show much. Assuming assembly isn't an issue, what was the condition of the piston bore before the rebuild? Was is smooth?

[johnl]

Bob, Unfortunately, I don't know much more than you do.  Just got it in the mail and this ex-Honda mechanic I know installed it.  Woe is me!

[Bob Wessner]

I know you don't want to hear this, but your problem is one that needs resolution. I think that means taking the M/C apart and having a look. Sorry.

[johnl]

Bob, I'm past the point of not wanting to hear the worst.  I am expecting that the M/C will have to come apart to resolve this issue.  I can't seem to get all the fluid bled out of the system but at this point the M/C is pretty much empty.  If I (can) pull the circlip and start removing parts, will I have to worry about a lot of brake fluid spewing out?

[Bob Wessner]

I would cover the nearby parts of the bike, particularly the paint work (brake fluid is a great paint remover) and disconnect the brake line at M/C and try to catch anymore fluid on something. Try suspending the brake line while it is off. Then remove the M/C. At least that's how I would go about it.

[johnl]

Thanks Bob.  I've already removed the M/C and am now going to do a little searching here on removing that dad-gummed circlip.  Wish me luck!

[johnl]

OK, I removed the little clip holding the rubber boot on, but now I can't seem to get the rubber boot itself off.  The dreaded circlip is behind the rubber boot,. right?  and there's nothing else holding it on correct?

[Bob Wessner]

Yes, once the round spring clip is out, then comes the rubber boot. It just protects the innards from dirt. Try grasping it and gently with some needle nosed pliers, tugging it at various places around the circumference. Can't guarantee it won't be damaged. I didn't concern myself with it too much when I did mine as a replacement came with the rebuild kit.

[johnl]

Thanks again Bob.  Got the rubber boot off, and not even damaged!   After that I used the awls I bought at Home depot to go after the circlip.  Long story short, I was just starting to get to the point where I was ready to use some 'colorful' language aimed at the circlip and thought, it's getting late, best to leave it for another day.  I think I'm going to dream about circlips tonight.  Thanks for all your help.

[Bob Wessner]

I went through the same "colorful language phase." I eventually went out and picked-up a pair circlip pliers. Even if I only used it one other time in my life, it was worth the cost. Had the clip out in a jiffy. Good luck. Let us know what you find once you get in there.

[Jonesy]

Try pushing the plunger down. I used a screwdriver leveraged against the brake lever pivot bolt. It makes accessing the snapring much easier with standard snapring pliers.