Low pressure brake , shop not sure ; help

Took car to shop, not sure, of fix! Low brake pressure ! Brake pedal locked at top FULL TIME, no time does it go down! Can’t drive. Tried fill mineral oil , to find oil push up out all over inner fender, hitting brake to stop. So not oil. Jag Bits said most likely not hyd pump. What can I have 2nd shop look for help please, desperate ! Not rich , and need fixed . Please help , don’t have but only glovebox service book. . No place can I find info but “take to dealer” abs light flashed couple times then was replaced by low brake and locked pedal. . If pressure goes back to reservoir , would this be valve open allow back to reservoir , and cause brake low pressure and lock pedal? Valve fail? Which one? Help please , what is way of telling hyd pump fail, worst hope ? 89 ( 88-89 early version, accumulator under radiator) xj40 VP