I have been working on the brakes for my T-bird and Raybestos tech gave me a
good diagnostic technique for air in the lines.
If you have bled your brakes and the pedal still pumps up you can find the
circuit with air in it this way. First be sure the master cylinder is full.
Then at all the brakes wrap the flex line in protective rubber (old inner
tube) and clamp the lines off with vice grips. Then test the pedal, it should
be high and hard, if not the master cylinder is where your problem begins.
If the brake pedal is high and hard the master cylinder is OK. Then start at
any brake position position you want to and release one of the vice grips.
Test the brake pedal again. If the pedal is high and hard the circuit tested
is not the problem. Replace the vice grip and test the remaining circuits one
at a time, always reclamping the lines after testing, until you find the
circuit that lets the brake pedal go soft. That is the circuit with the air
in it.
Best regards,
Tom
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