If you would like to test your flex hose for constrictions, [ which is common on vintage systems],
I use this simple test.
Raise each wheel to be tested off ground. Have someone press pedal down firmly for a moment. Then, after releasing pedal, try to turn the wheel by hand. If it does not release, quickly open the bleeder. If tire now turns, hose
is constricting.
The bad hose acts like a one way valve because the pedal pressure is so much more than the return pressure.[ hardly none].
So, essentually, the breaks work, but don't release.