Master Cylinder brake issues - ZX6R Forum
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post #1 of 28 Old 04-10-2017, 09:38 AM Thread Starter
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Question Master Cylinder brake issues

Hello all,

I recently fully flushed the front brake system and reset the caliper pistons on my 2001 ZX6R which has stock calipers, stainless lines and a 19RCS brembo master cylinder.
I don't believe I pulled the lever in at any time while the master cylinder was dry. I introduced Dot 5.1 back into the system by pouring it into the reservoir and then started to bleed the brakes by starting at the furthest caliper... I have now spent around 7hrs attempting to bleed and try various recommendations like syringes and other bleeding tips. I am to the point where I figure maybe the master cylinder has an issue because I have the brakes to a point where they get hard when you pump them but every initial lever pull is super easy and bottoms out quick...
I can hear an air sound when I pull in the brake lever and so I sprayed soapy water onto the rubber that the lever pushes into and whenever I pull the lever in it would bubble. I am not sure if that means the seals are gone or possibly a friend mentioned the plunger is stuck inside the master cylinder. I did zip tie the lever in last night and still no luck today. I am about to go out and try a few more things but I don't think it will help. Any help would be really appreciated as I suck with any brake jobs! If you need pictures or video to easen the mind I can try to come up with them.
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post #2 of 28 Old 04-10-2017, 10:11 AM
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From what you describe, I'd have thought it would be the seals in the M/C. If the piston were stuck, it should still maintain pressure within the system. Leaking seals would allow the pressure that sits in the M/C to escape.

A zip tie on the lever would only really work to get any tiny bubble of air that may still be caught in the line. If you're able to pull back right to the grip, a zip tie isn't going to do anything useful.

Assuming you didn't disconnect the calipers, lines, M/C or reservoir, I'd probably start by checking the internals on the master cylinder.

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post #3 of 28 Old 04-10-2017, 10:38 AM
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I could easily imagine you getting bubbles just from the motion of the rubber grommet on the MC. This may not be a good way of identifying issues there.

That said, I've had experiences where, 'Squeeze, crack the bleeder, tighten, repeat' was not working. I found that opening the bleeder, pulling a vacuum on a line from the bleeder (I did this with a long hose and my mouth) and making sure you're fed from the fluid reservoir is the best first step. Do this on the lowest caliper first, then the next, then the MC. This gets to the point where I can bleed normally.

Try that above if you haven't tried something like that yet. Otherwise, you might have an air leak somewhere. It could be time to inspect calipers, replace crush washers, check bleed nipples, and make sure you're airtight.

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post #4 of 28 Old 04-10-2017, 11:04 AM
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Sometimes the brembo can be a pain to bleed after flushing. You really need to start at your MC and work top to bottom. You gotta get some fluid going through the MC in order to bleed at the calipers. Also there is another way to bleed besides pump a few times, hold and then opening your zerg fitting. Try this:

1) Start at MC
2) Open Zerg Fitting
3) Pull break lever AND HOLD
4) Close zerg fitting
5) Pump breaks
6) Repeat

Its another way to bleed and anytime I do a flush its how I bleed the two calipers and MC and then go back around the other way. Also... Speed Bleeders are one of the most convenient upgrades I have done to my bike, available at STG.
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post #5 of 28 Old 04-10-2017, 11:07 AM
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Here, just found a STG video on youtube explaining this method. Its long but covers everything. Again notice how he STARTS at the MC and the method he uses.

Open
Pull break and hold
Close


Repeat until no air bubbles are present in tubing

Also, I use the bag he is showing, its about 11 bucks, and it really makes this job super clean and fast. The speed bleeders made by the same company really takes bleeding to an insanely easy process.

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post #6 of 28 Old 04-10-2017, 01:02 PM
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Any update bud?
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post #7 of 28 Old 04-10-2017, 03:05 PM
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I use a vacuum pump.. In your case.. Get a big horse syringe, PUSH the fluid back into the master cylinder.
They REALLY don't move air well.
Every Brembo I've seen have a bleeder at the master cylinder. Start there.
Will throw out a huge warning, in case you don't know.
Brake fluid strips paint better than most paint strippers. Cover ALL painted surfaces with a nice thick blanket.
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post #8 of 28 Old 04-11-2017, 01:34 AM Thread Starter
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Hey guys,

Here's for an update.. just to clarify I actually did fully take off the calipers and flushed them out so I could completely clean out the gunk of the calipers and reset the pistons..
I did adjust the 19RCS M/C to the 20 setting cause I read somewhere it may be better for 6pots. After doing so I couldn't hear a air sucking noise anymore.

I went out last night after posting this and tried firstly to bleed the M/C then undo the banjo at the M/C put my finger over the brake line hole while I pull in the lever slowly to make sure it shot fluid out.. ( which it did). I then didn't touch the lever before putting the banjo/lines back into the M/C. I then started bleeding with the M/C first. pump, loosen, tighten, repeat..
I gave up at the 3 hour mark due to frustration and loss of patience. The lever still pumps up really hard but always bottoms out on the initial pull. At this point I feel like I have heard every possible recommendation there is. Even passer bys claiming they could bleed it right up within 10 minutes failed. I do know with brakes any amount of air can make you start over.

I already came to the conclusion for the paint that it will need to be redone

Last edited by rageyoudown; 04-11-2017 at 01:36 AM.
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post #9 of 28 Old 04-11-2017, 04:11 AM
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Did you purchase this Brembo MC new? Have you used it before or did you just put it on now?

A picture of the way your lines are routed might also help as clearly something is not right.
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post #10 of 28 Old 04-11-2017, 04:23 AM
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Quote:
Originally Posted by PainfullySlo View Post
Did you purchase this Brembo MC new? Have you used it before or did you just put it on now?

A picture of the way your lines are routed might also help as clearly something is not right.
I hope its not one of those $99 eBay Brembo MC specials...
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post #11 of 28 Old 04-11-2017, 11:48 AM Thread Starter
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The Brembo MC has always been on the bike since I bought it and only recently started having issues when the reservoir bracket broke. I have stainless lines 1 going to each caliper. I took it to a garage and when they tried a vacuum bleed even after the nipple was closed on the MC it still had air coming out.. We swapped the nipple to one that wouldn't leak air and adjusted the lines at the banjo fitting but still wouldn't properly pressurize.

If incase I have to purchase another MC any recommendations on the cheaper side? The older fireblade/CBR master cylinders don't look bad.
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post #12 of 28 Old 04-11-2017, 12:02 PM
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Did you re-use the crush washers?


Are you sure they are all good and all the banjo bolts are tight?

if yes.......... pull the caliper off the fork/rotor..........push all the pistons all the way in---essentially forcing all fluid and air in that caliper and line up into the master and eventually harmlessly into the reservoir

reinstall caliper

then do the other side

then pump it all up and start the bleeding procedure

depending on how full your reservoir is, you may have to empty it some to do this
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post #13 of 28 Old 04-11-2017, 01:02 PM
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Quote:
Originally Posted by rageyoudown View Post
The Brembo MC has always been on the bike since I bought it and only recently started having issues when the reservoir bracket broke. I have stainless lines 1 going to each caliper. I took it to a garage and when they tried a vacuum bleed even after the nipple was closed on the MC it still had air coming out.. We swapped the nipple to one that wouldn't leak air and adjusted the lines at the banjo fitting but still wouldn't properly pressurize.

If incase I have to purchase another MC any recommendations on the cheaper side? The older fireblade/CBR master cylinders don't look bad.
If you're gonna bin it, I'd give the Brembo MC a shot, see if I couldn't make it work.
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post #14 of 28 Old 04-11-2017, 02:51 PM
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Quote:
Originally Posted by rageyoudown View Post
[...] If incase I have to purchase another MC any recommendations on the cheaper side? The older fireblade/CBR master cylinders don't look bad.
I got a radial master cylinder from an '07 model (although, it was fitted to a ZZR1400) and it works beautifully. It was only about 45 quid on eBay. Admittedly, it's a very tight fit. I've been told the units from the '06+ model R1/R6 are smaller and work really well. There's a few of those floating around too.

Unless the Brembo has a cracked body that's causing the leak, it'd probably be cheaper to try to get it repaired than replace it. Service kits, nipples, etc are much cheaper.

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1999 ZX6R (G2) - Pipewerx exhaust (dB killer removed) | Dynojet Stage 1 | K&N air filter | flushmount front LED indicators | Clear LED tail light with integrated indicators | Scottoiler eSystem | Pyramid Plastics hugger | HID headlight | Stubby levers | HEL braided steel lines | 07 ZX6R radial master cylinder | Bar-end mirrors | Double-bubble screen | Crash bobbins | one hell of an anal-retentive owner.
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post #15 of 28 Old 04-12-2017, 03:34 AM Thread Starter
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When I was bleeding last night I could never get any air out of the calipers just straight fluid, but the M/C on the other hand would pull tons of air each time and never actually just do full fluid. No matter how many times you pumped and bled.

This is after I changed the nipple to one that wouldn't leak air and adjusted the lines to not push on each other.
My next and maybe last couple ideas is to change all of the copper crush washers but I'm not sure completely on what size to get.

Last edited by rageyoudown; 04-12-2017 at 03:41 AM.
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