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Bleeding brakes....

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OneWheelDrive
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Bleeding brakes....

Post by OneWheelDrive on Mon 02 Mar 2015, 6:37 pm

Hello,

  as part of my ongoing bike refurbishment, I've fitted braided brake-lines front and back.  I drained most of the brake fluid from both reservoirs at the same time and now I've refilled the rear reservoir and spent the evening trying to bleed the rear system.

  The problem is that, no matter how much pumping of the brake lever I do, no fluid goes into the system from the reservoir and no pressure builds up.  So far, I've tried pumping the brake lever with the reservoir cap and diaphragm on and off, with the bleed-nipple open and closed and every combination of the two I can think of.  The Haynes manual says I should pump the lever with the bleed-nipple closed and then open it with the lever held down, but as no pressure builds up, no fluid comes out of the nipple (I've got a bleeding kit with a one-way valve attached to the nipple).

  Everything I've read says that bleeding the CB500 brakes is so easy, it's nigh-on impossible to get it wrong, so what's going on?

  The brakes were working fine before I fitted the new hoses...any thoughts would be much appreciated!

Thanks Smile
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teamster1975
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Re: Bleeding brakes....

Post by teamster1975 on Mon 02 Mar 2015, 7:20 pm

Did you replace the copper banjo washers? (Or anneal them?)
It sounds like air getting in somewhere.
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OneWheelDrive
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Re: Bleeding brakes....

Post by OneWheelDrive on Mon 02 Mar 2015, 7:38 pm

Hello,

  yep, the new lines came with new washers and they're all torqued up properly - there's not fluid leaking out anywhere - the level in the reservoir doesn't change at all and no air comes up from the master cylinder...

  I was wondering whether I should try to "prime" the new lines by filling them with fluid...I don't really know how I'd do that, though...

  Thanks for your help, though Smile
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jchesshyre
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Re: Bleeding brakes....

Post by jchesshyre on Mon 02 Mar 2015, 7:41 pm

I would start by pumping the lever with the bleed nipple open until fluid does come out, then proceed with the bleeding procedure.

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Re: Bleeding brakes....

Post by Guest on Mon 02 Mar 2015, 7:42 pm

How about holding in the brake lever and then suck out the air via the bleed nipple?
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teamster1975
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Re: Bleeding brakes....

Post by teamster1975 on Mon 02 Mar 2015, 7:50 pm

I highly recommend a vacuum bleeding kit. It makes life so much easier!

For now though, undo the banjo at the caliper end and see if you can get fluid to it by pumping the pedal!
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Stooby2
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Re: Bleeding brakes....

Post by Stooby2 on Mon 02 Mar 2015, 8:12 pm

Undo the banjo bolt at the reservoir end as if it was a bleed nipple - press the lever in, loosen the bolt, let air out, tighten - and repeat until only fluid comes out. Then bleed from the bleed nipple. Put plenty of cloth under the resevoir to catch the fluid. 

I had exactly the same problem and this cured it.
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HomeBrew
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Re: Bleeding brakes....

Post by HomeBrew on Mon 02 Mar 2015, 8:17 pm

Buy the vacuum pump. Seriously it saves a hell of a lot of hassle http://www.ebay.co.uk/itm/UK-Deluxe-Hand-Held-Brake-Bleeder-Tester-Set-Bleed-Kit-Vacuum-Pump-Car-Motorbike-/251501769708?pt=LH_DefaultDomain_3&hash=item3a8eac73ec

Otherwise your new lines are full of air that can't be pumped by the master cylinder, you have to suck the new brake fluid down the line. It won't hurt if it gets in your mouth, just make it numb.
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OneWheelDrive
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Re: Bleeding brakes....

Post by OneWheelDrive on Mon 02 Mar 2015, 8:39 pm

Thanks very much, all - that makes sense.

I'll definitely give the banjo-bolt loosening method a go - if I have no luck that way, I think I might give the taste of brake-fluid a miss, so the vacuum kit off ebay looks like the best bet Smile

Thanks for your help!
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OneWheelDrive
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Re: Bleeding brakes....

Post by OneWheelDrive on Mon 02 Mar 2015, 9:41 pm

Well...seeing as everything on TV tonight was spherical and in the plural, I went out to the shed and tried the whole loosening off the banjo-bolt at the reservoir end method - I had the brakes full of fluid and bled in under five minutes...in fact, probably in under two minutes!

As far as top tips go, that's one everybody should know!

Thanks, Stooby2!
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eternally_troubled
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Re: Bleeding brakes....

Post by eternally_troubled on Tue 03 Mar 2015, 3:14 pm

Glad to hear you got it working.

I suspect that loosening one of the top banjo bolts provides an easier method for air to escape, which means the brake fluid drains more easily out of the reservoir into the line. Once the line is mainly full (when the fluid spills out of the open banjo, rather than the air) you don't have the air-lock problem and it works 'like normal'.
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badseeds
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Re: Bleeding brakes....

Post by badseeds on Tue 03 Mar 2015, 3:21 pm

This should be made a sticky post. I don't know how Sad
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Stooby2
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Re: Bleeding brakes....

Post by Stooby2 on Tue 03 Mar 2015, 5:21 pm

Glad you got it sorted  cheers
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teamster1975
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Re: Bleeding brakes....

Post by teamster1975 on Tue 03 Mar 2015, 6:20 pm

@badseeds wrote:This should be made a sticky post. I don't know how Sad

You can do that you know matey Wink
I'll knock up a quick how-to as it's not obvious Smile
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ceejay
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Re: Bleeding brakes....

Post by ceejay on Thu 12 Mar 2015, 11:44 am

@HomeBrew wrote:Buy the vacuum pump. Seriously it saves a hell of a lot of hassle http://www.ebay.co.uk/itm/UK-Deluxe-Hand-Held-Brake-Bleeder-Tester-Set-Bleed-Kit-Vacuum-Pump-Car-Motorbike-/251501769708?pt=LH_DefaultDomain_3&hash=item3a8eac73ec

Otherwise your new lines are full of air that can't be pumped by the master cylinder, you have to suck the new brake fluid down the line. It won't hurt if it gets in your mouth, just make it numb.

I want to buy one of these as I could do with one for my car as well, just wondered if anyone with experience of them can see any obvious differences between the one above and this one below and if so is it worth the price difference?

http://www.ebay.co.uk/itm/Hand-Held-Brake-Bleeder-Tester-Set-Bleed-Kit-Vacuum-Pump-Car-Motorbike-Bleeding-/380763094231?pt=LH_DefaultDomain_3&hash=item58a73fbcd7

Thanks
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HomeBrew
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Re: Bleeding brakes....

Post by HomeBrew on Thu 12 Mar 2015, 4:21 pm

No they look exactly the same. Mine cost £17. The rubber O ring for the bottle can fall out watch out.
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ceejay
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Re: Bleeding brakes....

Post by ceejay on Thu 12 Mar 2015, 4:28 pm

thanks, worth a go for 14 : )
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teamster1975
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Re: Bleeding brakes....

Post by teamster1975 on Fri 13 Mar 2015, 5:17 pm

A little tip, put a jubilee clip around the bottle to stop it collapsing with the vacuum Smile

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