I have a 93 XJS with ABS brakes. What I get is the pedal to the floor with no pressure at all. Pumping does nothing. I flushed the system and still nothing. Logic would say the master cylinder is bad, but this is an ABS system and I am lost. There are no fluid leaks anywhere. Help!!

 

As your pedal is going straight to the floor it could well be the master cylinder. The master cylinder is a convoluted assembly that Jag calls an 'activation unit' and it basically combines a master cylinder with a hydraulic booster and all kinds of valves. Unfortunately there does not appear to be a rebuild kit for the MC which is strange? New ones are very pricey but you may be able to find a used or rebuilt unit for $500-800. I'm not sure why they made it so complex, they went back to much simpler design in 1995.

Cheers,

Allan