Brake Master Cylinder(Getting Pressure back)

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Brake Master Cylinder(Getting Pressure back)

Postby Gman » Thu Jul 16, 2009 1:02 pm

It commonly comes up that once the level of the Master Cylinder has dropped whilst servicing the brakes people have trouble
getting the fluid to flow back through the system.Some people buy expensive Vacs to do the job.These are not needed.It's very easy once you know how.

1:Slack off the bleed nipple on one of the brake calipers and fit your brake bleed kit(I use a clear plastic pipe in a Clear Glass with some old brake fluid in it and the pipe under the fluid).

2:Top up MC

System 1:A Spit on your hand or not allergic smear some clean brake fluid on it and press onto the top of the MC to form a seal.When you now pump the lever with a bleed nipple open you should feel a vacuum form and pull at your palm,

System 2:

Remove Main MC Banjo bolt.
Place your index finger of your right hand over the MC hole whilst holding the banjo bolt and line ready

4:Pump the lever smoothly a few times.
You should feel pressure build and push your finger away a little in "B" above or just come through in"A" but keep pressure on and off the hole by feel.After a few squeezes you should get fluid squirting through.

5:Quickly get the Banjo bolt in and tighten.

6:Medium speed pump and hold the lever several times and you should see air bubble start to appear in the clear can now keep pumping until all the air is out.I do the right hand side and then the left and then the right and then the left again on my Dual disc CX just to be certain.

If you don't get any pressure at 4 then there's a fault with your Master Cylinder.
The above technique has never let me down and is a lot easier than typing it in practice.
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Re: Brake Master Cylinder(Getting Pressure back)

Postby Weevee47 » Tue Mar 09, 2010 6:05 pm

Also, if after bleeding the system through, your brake lever feels spongy, pump it a few times until it gets as hard as it is going to get, hold the lever in and place a cable tie around the lever and handlebar, keeping the pressure on. Leave until next day and cut off the cable tie, presto, nice firm lever pressure!
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Joined: Wed Oct 07, 2009 10:22 pm
Location: Peterhead, NE Scotland.

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