Brake failure on 1994 Jaguar XJS

'94 XJS with 88K miles, ABS brakes. Normally excellent brakes. Now pedal pressure is spongy and stopping is very poor (dangerous). No leaks, fluid remains topped off. On occasion, left front caliper drags, smokes, and pedal goes to floor with virtually zero stopping ability. What part(s) might likely be responsible? Please help.....

Asked by for the 1994 Jaguar XJS
Have your car towed to a good shop that can deal with Jaguar ABS and brake hydraulic problems ASAP, before you have an accident!!
There are several components that can cause this such as defective calipers, defective ABS solenoids etc.

here are some shops:
1 more answer
Owner's followup: Talked with service manager at Jaguar dealership, and several mechanics specializing in Jaguars. All said that it would take diagnosis (shop time, prices ranged from $60 - $120/hour) and sounded "expensive." Brother-in-law and I spent a couple of hours bleeding the brake lines. Pedal is now high and firm (normal) and the car stops very smoothly. It appears like the previous owner had a new rotor, pads and caliper rebuild on the left front wheel. Probably didn't properly bleed the lines. I am still driving it cautiously....but it appears to be cured.