911 CARRERA NON-TURBO
Components of system include a connecting vent hose between crankcase and oil tank, a main vent hose with orifice between the oil filler tube neck and air intake duct above throttle, an auxiliary vent between oil tank and intake port below throttle, vacuum control, air switching valve, and temperature switch.
Crankcase vapors and blow-by gases flow into oil tank, where excess oil is separated from gases. At temperatures above 50°F (10°C), gases are drawn into intake manifold through main vent system. At temperatures below 50°F (10°C), temperature switch opens allowing vacuum to open auxiliary vent passage in air switching valve. Gases are then drawn into engine through auxiliary vent to prevent throttle icing.
Crankcase Ventilation System (911 Carrera - Non-Turbo). Scheme 1
911 CARRERA TURBO
Components of the system include an oil trap, oil tank breather line, crankcase breather line and oil return flow line.
An oil trap, located on the right-hand side of the engine compartment, is connected to the crankcase breather line. Crankcase gas flows from the crankcase, passes through the oil trap and enters the air cleaner. A return line from the oil trap connects with the crankcase.
Crankcase Ventilation System (911 Carrera - Turbo). Scheme 2
928S
During idle and low speeds, crankcase gases travel from the oil trap, (at base of oil filler neck), through connecting hose to cylinder valve cover between cylinders No.1 and 2. Gases pass through another oil trap (inside valve cover), into a restrictor (inside elbow on valve cover), through connecting hose to the intake air distributor.
A safety valve, installed in oil filler neck, opens at pressure of 80 to 100 mbar to guide the crankcase gas direct to the air guide housing.
At high speeds, crankcase gases pass through a restrictor (at top of oil filler neck), to mix with fuel tank gases through a connecting hose into the intake air distributor.
Crankcase Ventilation System (928S). Scheme 3
944, 944 TURBO
Blow-by gases leave crankcase through a cast riser bore and then enter ventilation dome in the oil filler neck. The ventilation dome acts as an oil trap for gases. From the trap, gases are routed to engine intake through a flow valve and connecting hoses for combustion.
Any trapped fresh oil passes through a drain tube and into the oil pan. The flow valve prevents blockage due to freezing by very low ambient temperature.
Crankcase Ventilation System (944). Scheme 4
TESTING
Note. Testing information not available.
MAINTENANCE
Inspect the system's operation and hoses every 30,000 miles. For proper operation of crankcase ventilation system and engine it is important that oil filler cap and all connections be tight, not allowing the intake of any additional air.
Poses Online