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
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.