General information
The crankcase ventilation system prevents exhaust gases from entering the atmosphere. Fresh air is directed through the air filter through the ventilation hose into the engine crankcase and mixed with the purge gases there. The exhaust gases are sucked in by the intake manifold through the crankcase ventilation valve. The crankcase ventilation valve raises the piston depending on the given intake manifold pressure and thus regulates the flow of exhaust gases. In other words, when the engine load is low, the exhaust gases help to stabilize the engine, and when the load increases, the flow increases, thereby improving the ventilation capacity.
Pic. 6.1. Diagram of the crankcase ventilation system
Pic. 6.2. Location of the crankcase ventilation valve 4G1 | 
Pic. 6.3. Location of the crankcase ventilation valve 4G9 |