Master Cylinder & Bleeding Brakes
The master cylinder:
This is where the pressure is created & converted from non - hydraulic pressure to hydraulic pressure. Brake fluid is held in the reservoir, when the brake pedal is applied it pushes against the push rod which then pushes the piston. At the end of the piston is a L-type seal which helps keep the pressure & stops the fluid getting past into the non - pressure side of the cylinder.
Brake Bleeding
When bleeding brakes a small hose is usually connected to the bleeder nipple & using an 8mm spanner to open the nipple. Pump the brakes till pressure starts to build up, then hold the pedal, Open the nipple & the pressure will release by pushing on the pedal. This will push out any old fluid & all so get rid of any air bubbles if there are any.
Further down this blog is more ways to bleed brakes.
The master cylinder contains:
2x Pistons - Primary piston is at the front, Secondary piston is at the back.
1x Reservoir - which holds the fluid
1x master cylinder body
3x L-type seal
1x O ring
1x Circlip - This helps hold in all of the above
Pressure Testing The Master Cylinder:
When pressure testing the master cylinder first we must block off the primary & secondary circuit with a couple of bolts.
Fill the reservoir up fluid, then slightly loosen the bolts. Then proceed to push on the primary piston with something solid, this will push out all the air bubbles, then tighten the bolts back up.
Then we push back on the primary piston, if there is no pressure build up on the pistons & pressure is being lost then we there is a problem/ leak somewhere inside.
The video below is showing how this is all done!
There are many ways you can drain the fluid from the reservoir.
1. Gravity fed - This is where a small hose is attached to the bleeder nipple. The bleeder nipple is then opened & the fluid slowly drips in to a container.
2. Attach small hose to bleeder nipple & pump the fluid out by pumping the brakes.
3.Attach a Vacuum Brake Bleeder to the bleeder nipple, open nipple. Vacuum Brake Bleeder will then suck the fluid out.
The video below will show how we got the fluid out of the reservoir.
Gravity Drip
Brake Vacuum Bleeder
To the left is the vacuum bleeder.
This is hooked up to a air compressor & the white hose is connected to the brake bleeder nipple.
When the vacuum bleeder is connected the we connect the reservoir filler, after it has been filled with brake fluid.
The vacuum is then switched on & the old fluid is sucked out & replaced with new fluid straight away.
The video below shows the vacuum brake bleeder working!
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