• Required reading for all forum users!!!

    Welcome!
    Register to access the full functionality of the GSResources forum. Until you register and activate your account you will not have full forum access, nor will you be able to post or reply to messages.

    A note to new registrants...
    All new forum registrations must be activated via email before you have full access to the forum.

    A Special Note about Email accounts!
    DO NOT SIGN UP USING hotmail, outlook, gmx, sbcglobal, att, bellsouth or email.com. They delete our forum signup emails.

    A note to old forum members...
    I receive numerous requests from people who can no longer log in because their accounts were deleted. As mentioned in the forum FAQ, user accounts are deleted if you haven't logged in for the past 6 months. If you can't log in, then create a new forum account. If you don't get an error message, then check your email account for an activation message. If you get a message stating that the email address is already in use, then your account still exists so follow the instructions in the forum FAQ for resetting your password.

    Have you forgotten your password or have a new email address? Then read the forum FAQ for details on how to reset it.

    Any email requests for "can't log in anymore" problems or "lost my password" problems will be deleted. Read the forum FAQ and follow the instructions there - that's what we have one for...

  • Returning Visitors

    If you are a returning visitor who never received your confirmation email, then odds are your email provider is blockinig emails from our server. The only thing that can be done to get around this is you will have to try creating another forum account using an email address from another domain.

    If you are a returning visitor to the forum and can't log in using your old forum name and password but used to be able to then chances are your account is deleted. Purges of the databases are done regularly. You will have to create a new forum account and you should be all set.

Front Master Cylinder Leaking

Vmass

Vmass

Forum Sage
Past Site Supporter
I rebuilt the front brakes recently. I thought I did a good job, apparently not.

I noticed pressure loss and did a little checking. I thought I found the leak source when I rubbed my finger under the left front caliper and found some fluid. I ordered another rebuild kit in anticipation of rebuilding it over this weekend, along with replacing the tach seals.

I thought I would get a jump on the tach seal and pull the housing. I decided to check the front brake lever and it was very spongy.

Then I noticed a leak around the master cylinder. I drained the system and dismantled the reservoir.

It looks like it was leaking through the bolt holes that hold the MC/brake lever to the bars. Which if I am reading it right, means that fluid is getting into the chamber that is only meant for air? There was definately residual fluid in the second chamber.

Any ideas?
 
It looks like it was leaking through the bolt holes that hold the MC/brake lever to the bars.
Click to expand...

This part really confuses me. How is that possible? The fluid chamber is sealed to the screws at least the screws don't penetrate it.

Apart from that I would think that leakage could occur if the piston and seals weren't installed correctly or the sight glass was cracked or came lose.

Can you provide a pic to show?

Cheers,
Spyug
 
spyug said:
This part really confuses me. How is that possible? The fluid chamber is sealed to the screws at least the screws don't penetrate it.

Apart from that I would think that leakage could occur if the piston and seals weren't installed correctly or the sight glass was cracked or came lose.

Can you provide a pic to show?

Cheers,
Spyug
Click to expand...

You are thinking of a different MC. This is the rectangular type with the plastic see through reservoir, no sight glass.

Once the reservoir is removed, there are two chambers. One for fluid and the other for air. The bolts to hold the MC to the bars go straight through to the air chamber, where I believe the fluid was coming from.

I am not sure if my terminology is correct and I do not have access to pictures at this time.
 
The only way the MC can leak is if the O ring on the bottom of the reservoir (part no 59686-49000) is knackered or you have a rough edge on the bottom of the reservoir. When you re-assembled the MC did you twist the reservoir to line it up and was the o ring dry? If so it can tear / buckle etc.

However, have you checked the piston bore? MC leaks can be deceptive.

For your caliper leak have a real close look at your pistons (use a magnifying glass). I had one with the tiniest pock mark on it - I probably wouldn't even be able to see it with my eyes now - and that was enough to fail. Or again, you may have twisted a seal if you put it back together dry.
 
hampshirehog said:
The only way the MC can leak is if the O ring on the bottom of the reservoir (part no 59686-49000) is knackered or you have a rough edge on the bottom of the reservoir. When you re-assembled the MC did you twist the reservoir to line it up and was the o ring dry? If so it can tear / buckle etc.

However, have you checked the piston bore? MC leaks can be deceptive.

For your caliper leak have a real close look at your pistons (use a magnifying glass). I had one with the tiniest pock mark on it - I probably wouldn't even be able to see it with my eyes now - and that was enough to fail. Or again, you may have twisted a seal if you put it back together dry.
Click to expand...

I have a new rebuild kits on the way, for both the MC and caliper.

I recall having a heck of a time with the MC, just don't recall exactly what the issues were.

I am thinking that I could have damage something or intalled something incorrectly, within the master cylinder assembly.

If I did, is it possible for the fluid to get it the reservoir that is not sealed...because that is what it looked like.
 
Justa follow up describing the leak in more detail as well as asking the question again:

It appeared to me as if the fluid had come up through the air passage hole in the unsealed reservoir, located under the cup. The fluid then came out of the bolt holes that hold the MC to the bars.

Has anyone seen this happen before? The brakes actually were performing quite well. A little spongy by todays standards, but adequate.
 
Well, I rebuilt the caliper again and it seems fine know. I am not 100% certain, but I believe the piston cup set was not seated properly, allowing fluid to get on the wrong side of the piston and get pushed up in to the dry reservoir.

Got it?
 
You must log in or register to reply here.
Back
Top