Crankcase ventilation system — general information [Toyota RAV4 XA20]

1. When the engine is running, a certain amount of gases formed as a result of fuel combustion penetrate through the piston rings into the engine crankcase (crankcase gases). To reduce emissions of unburned hydrocarbons (HC) from the crankcase into the atmosphere, the crankcase ventilation system operates in a closed cycle, crankcase gases and oil vapors are extracted from the crankcase and fed into the intake manifold and then into the combustion chambers for subsequent afterburning in the cylinders during engine operation.

2. Crankcase gases and oil vapors pass through a hose connected to the valve cover into the intake air duct. The oil separator in the valve cover separates oil particles contained in the crankcase gases and feeds them back into the engine crankcase. Once in the intake manifold, crankcase gases mix with incoming fresh air and are burned during the normal fuel combustion process.

3. A coked oil separator, vent valve or hose will cause excessive crankcase pressure, leading to oil leaks and crankcase deposits. The condition of the components of the crankcase ventilation system should be checked in a timely manner and, if necessary, they should be cleaned or replaced. Before blaming the crankcase ventilation system for a malfunction, you should make sure that the main engine components are in good condition.

(View the original source on the website ToyotaMAN.ru)