Warm up the engine while driving until the coolant temperature gauge shows normal operating temperature.
Check and, if necessary, top up the coolant level, see section "Maintenance work".
Remove expansion tank cap.
Attention: When the engine is hot, before opening the cap of the expansion tank, in order to avoid burns from hot liquid or steam, cover the cap with a thick rag. Open the cover only when the coolant temperature is below +90°C.
Attach the tester with adapter to the filler neck of the expansion tank. Using the hand pump of the device, create an overpressure of approx. 1 bar. If the pressure drops by more than 0.1 bar within two minutes, the leak must be found and the cause eliminated. Leaks are detected by leaking coolant.
If no coolant leaks are visible, and the pressure in the system drops or even rises, then it can be concluded that there is a loss of coolant in the engine itself, for example, as a result of a defective cylinder head gasket or a crack in the housing.
To check the steam-air valve in the cap of the expansion tank, the cap must be connected to the device. Create an overpressure of approx. 2 bar with a pump. At the same time, steam (safety) the valve in the lid must open, otherwise the lid must be replaced.
Create a vacuum under the cover. At a vacuum of 0.1 bar, the air valve in the lid should open.