Quote:
Originally Posted by rusnak
Have the helper pump the pedal several times, then hold it down hard like in a panic stop. Open the bleeder screw with the helper holding the pedal down. If there is air, it'll come shooting out like crazy. Put a block under the pedal to keep it from going to the floor.
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This is very important for old cars and parts.
When the pedal is pushed fully to the floor:
-The piston/seal in the master cylinder bore travels to the end of the normally unused cylinder section.
-This section will be corroded and lumpy with rust after a decade or two.
-That action can break the high pressure M/C old rubber seal, resulting in a permanent sinking peddle with loss of brake pressure.
FWIW, the M/C reservoir gravity port and system is closed off with only an inch or two of pedal travel.
Sealed system then.