DESCRIPTION
The crankcase ventilation system for Audi vehicles consists of a rubber hose containing a metered orifice. Some models may contain an in-line PCV valve instead of a restricted orifice. The hose is connected to cylinder head cover at one end and the air cleaner at the other. The system is sealed and prevents crankcase vapors from reaching the atmosphere by drawing them into the air cleaner through a hose.
COUPE, 4000 & 5000
Crankcase vapors and blow-by gases from the crankcase are drawn into the cylinder head cover. Engine vacuum at the air cleaner draws the gases through the metered opening (or PCV valve) and into the hose which directs the gases to the air cleaner.
Here, the vapors and gases mix with the fresh incoming air and are drawn into the engine with the air/fuel mixture to be burned. This reburning of the vapors lowers the emission output of the engine.
QUATTRO
On Quattro models, at idle speeds, the PCV valve is nearly closed so that most of the crankcase fumes flow through a restrictor to the air duct above the air sensor plate. As pressure in the intake rises, the PCV valve opens directly to intake manifold. Under boost conditions, the PCV valve shuts and fumes are again routed to the air duct above the air sensor.
TESTING
Note. Testing information not available.
MAINTENANCE
Visually inspect the rubber hose between air cleaner and cylinder head for cracks, damage or restrictions about every 15,000 miles or once a year. If a strong smell of hot oil or increased engine noise is evident, check the system for leaks or possible disconnected hoses.
