Hydraulic Brake Servo System, Checking Operating Pressure

Test Prerequisites

-- Reduce operating pressure by depressing brake pedal approx. 20 times with engine NOT running.

If operating pressure is reduced, this can clearly be felt in brake pedal stroke (brake pedal stroke is shortened).

-- Remove left air duct.

-- Disconnect wiring from warning switch.

-- Remove warning switch.

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-- Connect hose of tester Pressure Gauge:VAG1441 to hydraulic brake servo using banjo bolt and copper seals that come with tester.

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NOTE:

Place thick seal between brake servo and fitting.

Place thin seal between fitting and banjo bolt.

-- Let engine idle until operating pressure shows over 140 bar (:2030 psi).

If pressure is not obtained:

-- Stop engine.

If the hydraulic pump is OK, pressure relief valve in pressure accumulator is malfunctioning:

-- Replace pressure accumulator.

-- Measure operating pressure again.

-- Reduce operating pressure by pumping brake pedal approx. 20 times with engine not running.

-- Remove tester Pressure Gauge:VAG1441 .

-- Install warning switch and check for leaks.

Tightening torque: 20 Nm (15 ft lb)

-- Check hydraulic fluid, top off if necessary.