Rear Brake Bleeding Problem (2011 Ninja 250) - Caliper Valve Sucks Back Fluid/Air

MovingUp7 · January 27th, 2013, 05:20 PM

I've spent hours searching forums for a possible solution to my issue -- and I've learned a ton! But apparently not enough.

Background on my bike: Purchased it 6 months ago with 10k miles and pretty great maintenance kept up on it. In great shape. To my knowledge, my rear brake had no issues prior to my attempt to bleed.

Problem surfaces: After successfully bleeding my front brake, I moved to the rear. Things started fine, when not 15 minutes into it, pushing the brake pedal all the way down and opening the caliper nipple/valve resulting in no more fluid being pushed into the tube. In fact, if I held the brake pedal down and left the valve open, it would suck air/fluid back into the valve. Odd. I even put my mouth on the other end of the tube and sucked in. Not much different.

Troubleshooting began. I unscrewed the MC banjo joint to open up the top of the MC. I pushed the brake down, covered the hole with my finger, and let the brake up (which evidently sucked fluid from the reservoir as the level in the MC eventually rose nearly to the top). It sat there for a moment, then I heard a gurgle, and fluid was magically pushed back up into the reservoir. Huh? I repeated the finger over the hole process, then put the banjo back on and tried bleeding again, no dice. I altered the angle of the bike so it wasn't leaning as much (air bubble near reservoir, perhaps?), and unscrewed the banjo joint right on top of MC. I blew fluid through the tube into the caliper until it came out at the banjo joint. I then resumed bleeding and progress was normal with some air mixed with fluid. Then, it started happening again! Nothing was going into my bleed kit tube, and after a little longer, it wanted to suck what was in the tube back into the caliper.

Somehow a vacuum is forming inside the line causing it to suck in through the valve, but not from the reservoir as it should. I read somewhere that pushing the brake all the way down can push the MC past where it usually goes in its bore tunnel and disrupt gunk, possibly leading to damaging the seals. By the way, the pistons and pads are pushed all the way out to the disc if that helps at all.

I am open to any and all words of advice/wisdom/tips!

Motofool · January 27th, 2013, 10:19 PM

Welcome to the site, Allan !

Sorry, I cannot understand your explanation; but someone else will post to help you soon.

cuong-nutz · January 27th, 2013, 11:16 PM

sounds like a bad MC or bad seals. I want to say you can disassemble the rear MC and take a gander at the seals. Is the rear brake adjusted properly?

MovingUp7 · January 28th, 2013, 08:46 AM

Cuong - I think you are right. I'll probably need to take it apart and look at it tonight. Never done it before, but I hope it is clear when something isn't working.

The fact that I'm not sure what you mean by the rear brake being properly adjusted probably means it isn't.

I didn't notice any problems before attempting to bleed though... Are you referring to brake pad movement?

January 27th, 2013, 05:20 PM	#1
MovingUp7 ninjette.org newbie Name: Allan Location: Nashville, TN Join Date: Jan 2013 Motorcycle(s): 2011 Ninja 250R Posts: 3	Rear Brake Bleeding Problem (2011 Ninja 250) - Caliper Valve Sucks Back Fluid/Air I've spent hours searching forums for a possible solution to my issue -- and I've learned a ton! But apparently not enough. Background on my bike: Purchased it 6 months ago with 10k miles and pretty great maintenance kept up on it. In great shape. To my knowledge, my rear brake had no issues prior to my attempt to bleed. Problem surfaces: After successfully bleeding my front brake, I moved to the rear. Things started fine, when not 15 minutes into it, pushing the brake pedal all the way down and opening the caliper nipple/valve resulting in no more fluid being pushed into the tube. In fact, if I held the brake pedal down and left the valve open, it would suck air/fluid back into the valve. Odd. I even put my mouth on the other end of the tube and sucked in. Not much different. Troubleshooting began. I unscrewed the MC banjo joint to open up the top of the MC. I pushed the brake down, covered the hole with my finger, and let the brake up (which evidently sucked fluid from the reservoir as the level in the MC eventually rose nearly to the top). It sat there for a moment, then I heard a gurgle, and fluid was magically pushed back up into the reservoir. Huh? I repeated the finger over the hole process, then put the banjo back on and tried bleeding again, no dice. I altered the angle of the bike so it wasn't leaning as much (air bubble near reservoir, perhaps?), and unscrewed the banjo joint right on top of MC. I blew fluid through the tube into the caliper until it came out at the banjo joint. I then resumed bleeding and progress was normal with some air mixed with fluid. Then, it started happening again! Nothing was going into my bleed kit tube, and after a little longer, it wanted to suck what was in the tube back into the caliper. Somehow a vacuum is forming inside the line causing it to suck in through the valve, but not from the reservoir as it should. I read somewhere that pushing the brake all the way down can push the MC past where it usually goes in its bore tunnel and disrupt gunk, possibly leading to damaging the seals. By the way, the pistons and pads are pushed all the way out to the disc if that helps at all. I am open to any and all words of advice/wisdom/tips!

January 27th, 2013, 10:19 PM	#2
Motofool Daily Ninjette rider Name: Hernan Location: Florida Join Date: Mar 2011 Motorcycle(s): 2007 Ninja 250 Posts: A lot. MOTY - 2016, MOTM - Dec '12, Jan '14, Jan '15, May '16	Welcome to the site, Allan ! Sorry, I cannot understand your explanation; but someone else will post to help you soon. __________________________________________________ *Motofool* *.................................Never ride faster than your guardian angel can fly* "Mankind is composed of two sorts of men — those who love and create, and those who hate and destroy. Love is the bond between men, the way to teach and the center of the world." - José Martí

January 27th, 2013, 11:16 PM	#3
cuong-nutz RIP Alex Name: Cuong Location: Houston, TX Join Date: Apr 2011 Motorcycle(s): '10 250r, '09 265r Posts: A lot. Blog Entries: 2	sounds like a bad MC or bad seals. I want to say you can disassemble the rear MC and take a gander at the seals. Is the rear brake adjusted properly? __________________________________________________ HalfFast Racing Team Serving Greater Houston Area Riders:WFO Riders MotoHouston HPC CMRA Ride Smart Fastline Lone Star Track Days

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January 28th, 2013, 08:46 AM	#4
MovingUp7 ninjette.org newbie Name: Allan Location: Nashville, TN Join Date: Jan 2013 Motorcycle(s): 2011 Ninja 250R Posts: 3	Cuong - I think you are right. I'll probably need to take it apart and look at it tonight. Never done it before, but I hope it is clear when something isn't working. The fact that I'm not sure what you mean by the rear brake being properly adjusted probably means it isn't. I didn't notice any problems before attempting to bleed though... Are you referring to brake pad movement?