Crankcase air bleed system (VW Golf 2)

The crankcase air exhaust system consists of an oil separator in the valve cover, connected to the air filter by a rubber hose. The reduced pressure generated in the air filter causes gases to be sucked in from the space above the valves. This space is connected to the crankcase. During combustion of the mixture, some of the gases (together with the remains of unburned gasoline) gets between the cylinder walls and the piston, under the piston or into the crankcase. It must be possible to freely pass these gases from the crankcase into the air filter, since the increasing pressure would cause oil to escape through the crankshaft seals or other gaskets. Since an oil mist is formed in the main crankcase during engine operation, the result of blocking the air outlet channels is that oil leaks out through the weakest gaskets. To prevent this, an air outlet system is used. In earlier models, the air outlet was screwed to the crankcase. In current models, the air outlet is built into the valve cover, where the oil is separated from the passing gas (photo 1.51), which then goes into the main crankcase. Hot oil vapors, as well as exhaust gases, together with unburned gasoline, are sucked into the air filter. This has two advantages: the car emits fewer pollutants and reuses unburned fuel. The amount of gases entering the air filter from the main crankcase can be used to assess the tightness of the piston-cylinder pair working together. The condition of the wire connecting the valve cover to the filter should be checked periodically. Cleaning the wire is only necessary for used engines.