Wash the hood outside and wipe dry. Unlock the service cover from the inside. Unlock the hood "arrow" and pull it forward a little. Remove the hood and lay it down with the side protected by the cover down. Disconnect hose "1" from the mount. Remove the engine casing. Unscrew the plug "arrow".
Connect the tandem pump tester "VAS 5187" as shown in the figure. Connect the diagnostic complex "VAS 5051". Start the engine and increase the speed to 1500 rpm. Observe the pressure readings on the pressure gauge: Prescribed value: at least 3.5 bar. If the specified value is not reached: replace the tandem pump.
After disconnecting the measuring device, tighten the plug to a torque of 25 Nm. The sealing ring must be replaced.