1996 Jaguar XJ12 Brake Service (ONLINE REPAIR MANUALS)

Master Cylinder

• Remove master cylinder as previously described.
• Carefully pry out master cylinder hydraulic line adapters from sealing grommets.
• Remove sealing grommets from master cylinder by levering out using suitable screwdriver.
• Press primary piston stop pin in to relieve secondary piston stop pin pressure.
• Remove front grommet sealing housing stop pin. Maintain pressure on primary piston and remove circlip.
• Remove primary/secondary pistons and spring assemblies by tapping master cylinder open flanged end on suitable wooden block. Compressed air may have to be applied to master...

Inspection

The following tests on the vacuum system should only be performed if the hydraulic system is in satisfactory condition.

• Raise and support front of vehicle. Ensure one wheel will rotate freely.
• Start engine and allow vacuum to accumulate.
• Apply brake pedal several times. Ensure wheel is free to rotate immediately after pedal is released.
• If brakes bind, booster is faulty.
• With engine running, apply brake pedal several times and check operation of pedal.
• If response is sluggish, check condition of vacuum hoses and booster unit air filter.
• Allow vacuum to build up, then...

Master Cylinder

• Remove brake fluid reservoir cap cover and disconnect brake fluid level indicator wires.
• Remove reservoir cap and filter.
• Drain fluid from master cylinder using suitable syringe.
• Disconnect and plug master cylinder brake lines.
• Oper...

Brake System Bleed

Bleeding the ABS system is not a routine maintenance operation and is only required when part of the system has been disconnected or the fluid is contaminated.

During the bleeding procedure, it is important that the level of fluid in the reservoir is maintained at approximately .0787 inch below the bottom of the filler neck. Motor/pump unit cannot charge accumulator if air and not fluid, is standing on low pressure side of pump.

If motor/pump unit, fluid intake hose or hydraulic unit of ABS system has been removed or disconnected, bleed as described under "Fluid In... "

• Raise and support vehicle.
• Start bleeding procedure at righthand rear wheel.
• Remove bleeder screw dust cap, then attach suitable one-way bleed valve and hose to bleed screw.
• Place hose end in suitable container, then loosen bleed screw ^1/2 turn.
• Pump brake pedal until clear, air...

The hydraulic booster increases pedal force by means of hydraulic pressure. The dynamic circuit of the rear brakes is supplied from the hydraulic accumulator via a control valve in the booster.

The pressure in the booster and rear brake circuit is proportional to the pedal force. The booster is composed of an actuating piston (1) and a booster piston (2), Fig. .

The movable , mechanical connection between the control valve (3) and two pistons is made by means of a scissor-lever mechanism (4), Fig. .

The control valve (3) opens the pressureless booster chamber to the reservoir (9). Sim...