Brake servo 334/D9781 JCB, OEM

Brake servo 334/D9781 is an OEM part for the JCB machines.

The brake servo sits between the pedal and the brake master cylinder and increases the force the operator applies to the pedal. The servo body is divided by a diaphragm into two chambers: one holds the low pressure from the vacuum pump, and atmospheric air enters the other when the pedal is pressed. The pressure difference pushes the diaphragm and adds force to the master cylinder piston. If the diaphragm tears or the servo valve leaks, the pedal becomes hard, much more force is needed to brake and a hissing sound may be heard when the pedal is pressed. The seal or O-ring between the servo and the master cylinder is renewed as well, since fluid leaking there can damage the servo diaphragm. After the servo is changed, pedal height and free play are checked against the maker's values.

Specifications

Compatibility

According to the product card, 334/D9781 is a brake servo. Fit is confirmed by the part number. The catalogue also has the aftermarket version of this part. Other parts are in Vacuum pumps and brake boosters.

Fitting

Before removing the servo, stop the engine and press the pedal several times to release the vacuum. If the master cylinder can be separated from the servo without disconnecting the lines, leave them in place. After fitting, check the push rod setting, bleed the system if necessary and test the brakes at low speed.