Expert: Sean Halliday - 5/2/2009

Question
I have a '96 Land Rover Discovery VIN starting with SALJY1242TA... It has a WABCO ABS system that is supposed to be rock-solid.
The brakes on this Rover used to 'cycle' every 5 or 6 presses of the brake pedal.  This cycling is somewhat disconcerting because the pedal pushes back against your foot during this cycle and you have no brake until pressure balances.  Previously you could release the pedal and reapply pressure to get brakes.
Recently while stopped at a drawbridge the brakes locked, even under full gas the Rover would only go about 5 mph.  Placing the car in Park, turning off the vehicle and restarting allowed the brakes to return to their 'normal' state.  The car made a thumping noise (engine side of the firewall) when the locked brakes released.
Within 30 miles the brakes completely failed.  No pedal pressure and the only way to stop the car is with the emergency lever.
I have replaced the master cylinder and attempted to bleed the brakes but get no pressure (looks like a gravity bleed) at the calipers.
One lead from the Master Cylinder goes directly into the Wabco ABS control and the other leads to a 1 in/3 out distribution block on the inside of the wheel well, adjacent to the steering column.  There appears to be moisture around that distribution point and it has an electrical connector on it.
What can I do to further trouble shoot without replacing these rather pricey components?
I've been told the ABS units very rarely go bad and the $6500 price tag is more than a bit prohibitive.
Any help or guidance you can give is greatly appreciated.

Answer
Did you consider the brake booster?The cycle factor is unusual and i would think this is not good.This system would need each component checked.This would be beyond the home mechanic as the abs unit is under extreme pressure and cannot be serviced without the proper tools.The abs unit as you say hardly ever goes out so im thinking the booster is leaking.I have seen these symptoms on a car that the booster failed.There is also the abs module to check,again,its a shop scanner to read this.