Caution! If the cooling system tightness test is performed after replacing the cylinder head gasket, first warm up the engine to operating temperature and then let it cool down. This ensures the tightness of the cylinder head gasket.
Caution! When the engine is hot, place a thick cloth on the radiator filler cap before removing it to avoid being burned by hot coolant or steam. Remove the cap only when the coolant temperature is below +90°C.
1. Turn the cap on the expansion tank 1/2 turn to the left to relieve pressure, and only then remove the cap.
2. Move the interior heating control to the maximum heating power position.
3. Check the coolant level in the expansion tank and top up if necessary.
4. Install the cooling system leak tester on the filler neck of the expansion tank. Using the hand pump of the measuring device, create a pressure of about 1.4 bar (see illustration).
[Original material on the website: www.mercedesman.ru]
Please note! The illustration shows an expansion tank that does not apply to A-class vehicles.
If the pressure drops, locate the leaks in the cooling system. Due to the high pressure, coolant will leak where there are leaks.
If the test pressure drops but there are no coolant leaks, this may be caused by coolant loss inside the engine, for example due to a faulty cylinder head gasket or a crack in the cylinder block.
Exhaust valve - check
The release valve is located on the filler cap of the expansion tank. It is designed to open the cooling system when a certain pressure is formed in it.
When the coolant heats up and expands, accompanied by the appearance of excess pressure, it opens and the excess coolant flows into the expansion tank.
5. Screw the radiator filler cap 2 onto the control device 1 (see illustrations 6.5).
The illustration shows a filler cap that does not apply to A-class vehicles.
6. Increase the pressure in the system using the measuring device pump.
The outlet valve should open at an excess pressure 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 cap is 1.4-1.5 bar.
Attention! There is an inscription on the cover indicating the pressure at which the outlet valve opens. This pressure is indicated as "bar x 100". This means that if, for example, the number "140" is indicated on the cover, then the valve opening pressure is 1.4 bar.