411 brake problem

[GREG]

Maybe try bleeding the brakes first and then start the car with your foot hard on the pedal -- the pedal should drop slightly and this shows the booster is working !
Then look for leaks around wheels, callipers,hoses, pipes etc

I suspect that if you are not seeing leeks anywhere that one of the servo/boosters has failed and the fluid has leaked inside them.

Fit new seals or buy an exchange unit. -- lots of fun :-)