How do U test this unit to see if it works,, I have bled all wheels and checked this system.. pedal is about l" from floor and hard..car seems to take too much pedal pressure to come to a complete stop...How do I test the diaphram to see if it is working? there is also an inline plastic valve which keeps vacuum in unit..how do I test this

The plastic valve is a check-valve, it is possible for one to stick closed. Quick test would be to bypass it and see if you had power brake function.

All of the brake booster failures I've had on domestic and Jap cars were evident by hard braking and quite a vacuum leak type noise from the unit when the pedal was depressed.

Justin B.