Jaguar S-TYPE & XJ 350/ 358 brake servo swap

Rob Hawkins travels to North Wales Jag Centre to find out how to fix this common problem with these models.

Brake servo failure on Jaguar’s S-TYPE and XJ 350/358 models is a frequent issue. Usually, when it happens, the brakes remain applied and can overheat the discs and pads. Gentle braking can give the feeling that the brake pedal is being pulled down. The brake pedal may feel hard and ineffective, and can fail to return to its original position.

Renewing the brake servo doesn’t affect the brake fluid in the braking system, so there is no messy brake bleeding required, unless the brakes have overheated and the brake fluid has boiled – in which case, the fluid must be renewed.

Although the job appears to be quite straightforward, Matt Norbury at North Wales Jag Centre warns against removing the brake light or cruise control switches in front of the brake pedal when changing

the servo. If they need to be detached for any reason, he says: “They must be removed with the brake pedal in its rest position, to avoid the switches firing the pins out. Likewise, when refitting them, do so last of all once the brake pedal is set and in its rest position. If removed, it is important to check they are set in the correct position.” Matt explains that the symptoms of incorrectly setting these switches include the brakes binding and the vehicle struggling to move in 'Drive' while at idle without the need for the accelerator to be pressed (the car should move on its own once in ‘D’ on the autobox). For example, if one switch is in the correct position and the other is fully extended, this may raise ABS and cruise control faults due to a pedal correlation issue.