Attention! If the cooling system leak test is performed after replacing the cylinder head gasket, warm up the engine to operating temperature first and then allow it to cool. This ensures the tightness of the cylinder head gasket.
Attention! With a hot engine, place a thick cloth over the filler cap before removing the radiator filler cap to prevent burns from hot coolant or steam. Remove the cover only when the coolant temperature is below +90°C.
1. Turn cap on expansion tank 1/2 turn to the left to release pressure before removing cap.
2. Move the interior heating control to the maximum heating power position.
3. Check up level of a cooling liquid in a broad tank and if necessary add a liquid.
4. Install the device for checking the tightness of the cooling system on the filler neck of the expansion tank. Apply a pressure of approx. 1.4 bar using the hand pump of the measuring instrument (see illustration).
Attention! The illustration shows a non-A-class expansion tank.
If the pressure drops, check for leaks in the cooling system. Due to the high pressure, the coolant will leak where there are leaks.
If the test pressure drops but there are no coolant leaks, this could be due to loss of coolant inside the engine, such as a defective cylinder head cover gasket or a cracked cylinder block.
Exhaust valve - check
The outlet valve is located on the expansion tank filler cap. It is designed to open the cooling system when a certain pressure is formed in it.
When the coolant is heated and expands, accompanied by the appearance of excess pressure, it opens and the excess coolant flows into the expansion tank.
5. Screw cap 2 of the radiator filler neck onto control device 1 (see illustrations 6.5).
The illustration shows a non-A-Class filler cap.
6. Pressurize the system with the gauge pump.
The outlet valve should open at an overpressure of 1.3-1.4 bar. Otherwise, replace the cap with a new one.
Attention! The opening pressure of the outlet valve of the new cover is 1.4-1.5 bar.
Attention! There is an inscription on the cap indicating the pressure at which the exhaust valve opens. This pressure is indicated as «bar x 100». This means that if, for example, a number is indicated on the cover «140», the valve opening pressure is 1.4 bar.