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Cannot for the life of me bleed my brakes

3K views 33 replies 14 participants last post by  a_morti 
#1 ·
I have a 2005 ZX10r I'm fixing up and I'm on the last legs. All i have left to do is clean up the wiring, bleed the brakes, put everything back on and she's all done for now. Easy, right? I've done all of that before. I am completely stuck on the brakes.

I replaced the brake lines, so now there's two brake lines in the front, one to each caliper. Admittedly, I've never had to bleed an empty system before. Anyway, I have gone through almost two bottles of brake fluid going with my "traditional method." I filled the reservoir up, and let gravity do the work and waited for fluid to start dripping out both calipers bleed valves, then tightened them up. Then I went one caliper at a time pressing the lever, opening the valve, closing, and repeating. Neither caliper has any air coming out and my brake lever still has precisely zero feel, literally no pressure or anything. I'm at a bit of a loss of what to do, I'm going to try reverse bleeding next.

Does anyone have any advice? I haven't tried reverse bleeding them yet, but I don't think my brake lever should have zero feel, even if there are some air bubbles left there should be some pressure right?
 
#3 ·
I’ve had pretty good luck using the banjo bolt at the M/C as a bleeding point. I place a rag under the fitting and just loosen the bolt enough to break the seal while moving the lever in. The bolt is usually the highest point in the system so air can naturally travels there.

Later, Doug
 
#5 ·
You can get banjo bolts with a bleed nipple on them.

 
#8 ·
Dowty washers?

Could be that the master cylinder seal has failed. There is one seal to build pressure and one to hold the fluid in. If the pressure seal fails, you'd never get pressure up. Can happen from it drying out over a period of being empty, also when bleeding the piston travels further than in normal use and can find dirt or corrosion spots it wouldn't usually hit, and tear the seal.
 
#12 ·
It would not be that unusual. When bleeding, the lever will come back all the way to the bar which it won't usually do. Plenty of chance to damage the seal. Or as it's been dry, the seals may have dried out. Won't cost you anything to pop the circlip out and have a look.

Or keep pumping gallons of fluid through, hoping for a different result.

Also would not be unusual to have a deformed copper washer. They can be just bad enough to let air in but not leak a noticeable amount of fluid.
 
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#17 ·
I ran duel lines on my zx9. Same issue there. I simply cracked the banjo bolt at the top like you would on the bleeder at the caliper. It gets the air out of the master. You will get lever pressure. Bleed at calipers after it stiffens up from bleeding you master and your good to go. If it still feels a little soft repeat process at master.

Sent from my SM-G960U using Tapatalk
 
#18 ·
Bled all the banjos a few times, still absolutely ZERO pressure. I'm going to go with the master cylinder rebuild since I don't really see any other option.

A thought I had, When I got the bike the guy who fixed it before me made it just passable to ride. One of the brake calipers wasn't connected and I assumed the previous owner didn't want to shell out money for 2 brake lines or maybe he didn't know it had 2 calipers when he bought the brake lines. But maybe it's something else. Is it possible that the caliper has an air leak somewhere? There are no fluid leaks but could air get in through a worn seal or something? Perhaps that's why that caliper was not connected to the brake system.

Sorry for the kinda dumb questions, I've honestly never had a problem with bleeding brakes and haven't yet needed to troubleshoot something like this up until now. Every brake system I've bled (besides this one, clearly) was pretty straightforward.
 
#22 ·
A caliper seal could be missing or torn. One of the seals between the halves could be missing or torn. We can't tell you what's wrong as we aren't holding the parts. But somewhere or other, you have air getting in, which is likely (but not definitely) also letting fluid out.

Brakes aren't hard, strip everything apart, inspect, clean/replace, put back together without getting fluid, oil or grease anywhere it doesn't belong... Can't go far wrong.
 
#23 ·
A caliper seal could be missing or torn. One of the seals between the halves could be missing or torn. We can't tell you what's wrong as we aren't holding the parts. But somewhere or other, you have air getting in, which is likely (but not definitely) also letting fluid out.

Brakes aren't hard, strip everything apart, inspect, clean/replace, put back together without getting fluid, oil or grease anywhere it doesn't belong... Can't go far wrong.
 
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#24 ·
#27 ·
Dude, haha. Go to Tractor Supply and a buy a 2 pack of syringes for livestock. Get the ones with the ends made for screw-on needles and you can screw your hose on to the end of the syringe. Hose won't pop off while pushing hard on the plunger. Last time I bought them they were $5 for a 2 pack. Save your blowing skills for da club. :fu:
 
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