Connect the test device (1) to the neck of the expansion tank (2).
Using the hand pump on the device, create a pressure of approximately 1.2 bar in the tank. If the pressure drops, there is a leak in the cooling system through which the coolant will leak.
Release the pressure and unscrew the connection on the expansion tank.
To check the safety valve in the expansion tank cap, connect the test device (1) to the cap (2). Create pressure with the hand pump. At a pressure of 1.4 to 1.6 bar, the safety valve should open.
Check the coolant level and, if necessary, top up the coolant to the "MAX" mark.
Install the cap on the expansion tank and, if the rubber sealing ring is damaged, replace it.