I am getting those same Brake and ABS lights on my dash too when I hit the brakes. The accumulator ball / sphere has a warning on it that it has brake fluid under pressure and to not loosen or remove. What procedure did you use to relieve the pressure before you removed the accumulator ball? Also, is the ball held in place by just that hex nut/bolt on top?

 

The accumulator stores fluid at around 100 bar/1,450 psi. I believe you can relieve the pressure by pressing and releasing the brake pedal repeatedly, with the engine off, until the pedal feels rock hard. Repeat at least 24 times to be safe.

The system is explained in the manual at this link:

Jaguar XJ40 Power Hydraulic System

The accumulator sphere is threaded onto the pump manifold. You may be able to loosen it using the hex socket, but I have typically used a strap-type oil filter wrench or a rubber-strap wrench.

Cheers,

Don

 

Thank you for the clear and concise answers. And the advice for removing the sphere is something that I may never have considered but seems like a great solution.