Checking Brake Master Cylinder [EK4]

Checking Brake Master Cylinder





- Ignition off.





- Connect test box and check ground points as per JA. Connecting test box. Connecting Test Box [JA]





- Disconnect control module.

First connect a temporary lead between #34 and #1 on test box. Then connect further temporary leads between #20, #38, #54 and #1 on test box.

NOTE: When the ignition is switched on, the inlet valves close. To prevent valves overheating, do not leave ignition on for more than 20 seconds. Wait at least 30 seconds before next test.

- Ignition on.





- Push brake pedal down hard as if braking suddenly.

Brake pedal should feel stiff and should not travel more than 40 mm (1.57").

- Ignition off.
- Remove the temporary leads.

If brake pedal is working OK:
- Try another hydraulic unit.

If brake pedal feels 'soft' or sinks:
- Try another brake master cylinder.