One man brake bleeder kit

DIYspanner said:
I've only flipped the master's seals once on an Astra back in the 80s. My practice of pushing caliper pistons back in the day was by using a lever which I believe pushed the fluid back up into the master too fast for the seals to cope with.
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With the brake pedal released, the port is open between brake lines and master cylinder, so pressure in the brake lines shouldn't affect the master cylinder piston seal at all. One way, the common way to bleed brakes is to pump it down from the master, towards the wheel cylinders. The less common way, sometimes used where the common methods fails, is to pump fluid in via the bleed nipple at the wheel, under pressure. Some even suggest this is the more logical way to bleed them, forcing air the way it naturally wants to go, up.
 
Makes sense, though it's not a smooth, continuous down hill run from master cylinder to calliper; if it were they would self bleed.
As long as the strategy employed moves the brake fluid fast enough that it's quicker than the speed a bubble drifts backwards against the flow when the bubble has encountered a local hill (such as a brake flexi hose that is a hump shape) then the system should bleed successfully.

Strategies that achieve a continuous flow may well do better than pulsed flow but you'd hope that the designers of brake systems would have the presence of mind to ensure that the volume of fluid moved by a depression of the pedal is sufficient to move an air bubble out of a place where it is stuck (top of a local hill) and to a place where if it came to rest it wouldn't drift back particularly quickly!
 
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