Emission Control Systems: Description and Operation

Engine Emission Control

Crankcase Ventilation

System Overview

NOTE: The vehicle emission vacuum routing diagrams are contained in the Description and Operation of Evaporative Emissions.

NOTE: Do not permanently remove or render inoperative any part of the vehicle emission control system including related hardware. Failure to comply may violate applicable state and federal laws.

The crankcase ventilation system gathers blow-by vapors from the crankcase and returns them to the intake manifold and air cleaner for combustion.

Component List

The crankcase ventilation system consists of the following components:

- a crankcase vent oil separator located on the engine block

- a valve cover vent hose connected to the air cleaner

- a crankcase vent oil separator hose connected to the intake manifold

- a crankcase pressure regulator located inside the crankcase vent oil separator housing

System Components

The crankcase vent oil separator removes vaporized oil from the blow-by vapors and returns the separated oil to the crankcase.

The crankcase pressure regulator controls the return of the blow-by pressure to the intake manifold through the crankcase vent oil separator hose.

The valve cover vent hose vents excessive crankcase pressure to the air cleaner and allows fresh air into the crankcase to prevent premature degradation of the engine oil.

System Operation

During high intake manifold vacuum situations the blow-by pressure flows through the crankcase pressure regulator and is returned to the intake manifold through the crankcase vent oil separator hose. During low intake manifold vacuum situations the crankcase pressure regulator restricts flow to the intake manifold causing blow-by pressure to flow through the valve cover vent hose to the air cleaner.