Engine crankcase ventilation (VW Golf 3)

Engine crankcase ventilation helps avoid excess pressure in the crankcase (arising from pressure losses during combustion). The gases are fed to the air filter housing and from there they enter the cylinder again, participating in the combustion process. A side effect, consisting in the gases carrying away oil particles, is used to lubricate the wear-prone inlet valve seat rings: The oil droplets lubricate to some extent the surfaces of the valve seals and valve seats. At the same time, there are not too many droplets and there is a pressure control valve at the outlet of the crankcase ventilation system, located on the cylinder head cover.

The picture shows the crankcase ventilation system of a turbodiesel engine. The pipe (3) leads from the cylinder block to the pressure regulating valve (2). The further channel goes straight from the cylinder head to the pressure regulating valve. From there a hose (1) goes to the intake part of the turbocharger. The arrow points to the safety clamp that holds the ventilation pipe at the junction with the engine block.

Note: The greater the loss of combustion pressure and the greater the wear of the pistons, piston rings and cylinder surfaces, the greater the smoke from the crankcase ventilation tube when the engine is running. With the oil filler hole open, pressure losses can be easily determined. Professionals can determine the degree of engine wear by the portion of air emitted.