Leaks in the cooling system and the operation of the safety valve in the cap of the expansion tank can be checked using a special device for testing the system under pressure.
Connect control device (1) to the neck of the expansion tank (2).
Using the hand pump on the appliance, pressurize the reservoir to approx. 1.2 bar. If the pressure drops, then there is a leak in the cooling system through which the coolant will exit.
Release pressure and unscrew the connection on the expansion tank.
To check the safety valve in the plug of the expansion tank, connect a tester (1) to the cork (2). Pressurize with hand pump. At a pressure of 1.4 to 1.6 bar the safety valve should open.
Check the coolant level and, if necessary, add coolant to the mark «MAX».
Install the plug on the expansion tank and, if the rubber sealing ring is damaged, replace it.