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Message started by LockeClone on 02/19/18 at 09:00:29

Title: Master cylinder busted?
Post by LockeClone on 02/19/18 at 09:00:29

...Or did I forget how to bleed brakes?

OK, so I flushed the system, changed out my pads and put a new braided line on.

Then I started the good ol' brake bleeding dance: pull lever, open system, close system, release lever and repeat. I did so until brake fluid was coming out with no bubbles. All good...

Except, when I pump the lever it never builds ANY pressure. It just bottoms out on the handle. I pumped it for 5 minutes straight and nothing. I took a screw driver handle and thumped at all the parts to try and dislodge air bubbles.

I have not bleed brakes for a good 5 years and I did nothing special to "prime or bleed the master cylinder" if that's a thing.

Thanks for the help.

Title: Re: Master cylinder busted?
Post by verslagen1 on 02/19/18 at 09:18:10

You seem to be saying several things out of order.

Once you replace the line, you've basically 'flushed' the system, as getting all the air out will require a small can of fluid.

Getting it to start is the tricky part. Seems if you got a bubble in the master it won't flow by pumping it.

A vacuum bleeder really helps, but you can loosen the top banjo bolt and pump it with the palm of your hand to start it. Once it leaks at the banjo bolt tighten it. Then you can start the bleeder dance.

Title: Re: Master cylinder busted?
Post by justin_o_guy2 on 02/19/18 at 09:25:31

did so until brake fluid was coming out with no bubbles. All good...

Once you get there, close the nipple, pump it up,

If she no pump up, and you got the air out, even if you had a bubble in it, you should get enough pressure to keep the lever off the bar.

Were you having a problem before you did all this?

Title: Re: Master cylinder busted?
Post by LockeClone on 02/19/18 at 18:16:50

@verslagen1
My order of operations was: Remove the fluid, remove the old line, remove the caliper, remove the old pads, install the new pads, replace the caliper, install the new line, put fluid in the reservoir...

Then, close the bleed valve, grab the handle, open the valve, close the valve, release the handle... The new fluid was running through the system, eventually without bubbles. But no pressure will build.

@ justin o guy2

I pumped for several minutes, hundreds of times after closing the nipple with a fluid-full system. No pressure, and the caliper doesn't move. I've done this before (years ago) and had an easy time of it, so I'm very frustrated.

Also, no problem before. My brakes were just a bit spongy so I wanted a braided line.

Title: Re: Master cylinder busted?
Post by Gary_in_NJ on 02/19/18 at 18:31:46

You've got trapped air. Go to a CVS and get a large syringe and then get some clear tubing..draw brake fluid into the syringe and fill the brake system from the caliper up to the brake reservoir. Once filled from the bottom up, rebleed the system.

Title: Re: Master cylinder busted?
Post by LockeClone on 02/19/18 at 21:47:34

Thanks Gary, buying a syringe sounds much better then looking for a master cylinder. I'll be able to try this sometime this week and I'll let yall know how it turns out.

Title: Re: Master cylinder busted?
Post by verslagen1 on 02/19/18 at 21:52:49

you might need to wrap the bleeder threads with teflon to minimize leakage.

Title: Re: Master cylinder busted?
Post by Dave on 02/20/18 at 03:13:32

To help with stubborn master cylinders.....I took a bleeder screw and drilled a hole through the center. The bleeder screw can then be tightened down and seated - but the hole allows a straight path though the screw and no air leakage. I use a vacuum bleeder to pull the fluid through.

After bleeding you can put a piece of Saran rap on the top of the master cylinder and wait for the gravity flow to stop......then remove the bleed screw and hoses with no additional loss of fluid from the master cylinder. Then when you have the stock bleed screw back in you can take the Saran wrap off the top of the master cylinder.