Brake booster/servo hazard check
 

Only noticed something amiss when following a truck down a steep Dorset hill with a T-junction at the bottom. First two brake presses alright then pedal very hard, and two feet needed on the pedal to stop car and just avoid collision – seemed brake servo (or booster) had insufficient vacuum reserve to power repeated brake use.

Safely home, the problem was any or some of - actual servo, its external one-way valve, the vacuum pump, and the tube connecting them.

Tube and valve proved alright, unfortunately, so expensive replacement looked likely.

Servo removal takes longer than in the past. One of the nuts on the four mounting studs above and behind the brake pedal requires patience, and brake pipe disconnection at the master cylinder is unavoidable. Once out, the cause of the problem was clear and is the reason that these few paragraphs are written.

Rainwater penetration through the driver’s side wiper spindle is intended to drain away through a funnel and tube arrangement incorporated in the wiper component mounting frame and away under the o/s /f wing. If this funnel is blocked with leaves and similar debris, water overflows and is channelled along the wiper frame to empty – you’ve guessed it - directly over the servo. Confirmation was found under the bellows at the pedal end – a semi-circle of heavy rusting. Water above this mark was apparently being drawn into the rear of the servo, resulting in its failure after 37K miles and 7 years.

Visual checking of the funnel and drain is possible by lifting the plastic panel at the rear of the engine bay on the driver’s side – just the same as when replacing pollen filter on the passenger side. The panel is held by plastic plugs - on mine removal is by pressing the centre down and gently levering.

Jaguar part number is XR856588 and can cost over £400.