Crankcase ventilation - Function - ra01006010040x(0040)

A. Standard version, B.Naturally aspirated and turbo-engines with exhaust gas re-circulation, Engines 601, 602 (except 602.98), 603 

A. Standard version 

Fig 1: Identifying Crankcase Ventilation - Standard Version

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Crankcase ventilation, naturally aspirated engine, standard version

Engines 601.91, 602, 603.91

The crankcase ventilation on standard version naturally aspirated engines is a closed, maintenance-free system.

The blow-by gases from the crankcase flow through the oil separator (126) into the cylinder head cover and a hose to the distribution pipe (140) on the intake manifold depending on the intake manifold vacuum.

These gases are distributed uniformly to all cylinders by the intake manifold and sucked into the combustion chambers together with the intake air.

The oil deposited in the oil separator runs back to the cylinder head through the return pipe (127).

Fig 2: Identifying Crankcase Ventilation - Standard Version Turbo-Engines

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Crankcase ventilation, standard version turbo-engines

Engines 602.96, 603.96, 603.97

The crankcase ventilation for the standard version turbo-engines corresponds to that of the naturally aspirated engines.

However on the turbo-engines after removal of the engine oil the blow-by gases flow from the cylinder head cover to the intake hose.

B. Naturally aspirated and turbo-engines with exhaust gas recirculation 

Fig 3: Identifying Crankcase Ventilation - Exhaust Gas Recirculation

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Crankcase ventilation on engines with exhaust gas recirculation

Engines 601.91, 602.91, 603.91

Engine 601.913 as of start of production

Crankcase ventilation on engines with exhaust gas recirculation

Engines 602.96, 603.96/97

Fig 4: Identifying Crankcase Ventilation - Naturally Aspirated Engines With Exhaust Gas Recirculation

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

The crankcase ventilation on naturally aspirated engines with exhaust gas recirculation differs from that of the standard version by addition of a built-in pressure control valve (141).

The pressure control valve is required because on engines with exhaust gas recirculation an additional throttle valve installed in the intake system results in significantly higher vacuums.

If the vacuum were too high, the engine oil would be sucked out of the crankcase.

The pressure control valve prevents this by keeping the vacuum constant above a certain value.

Pressure control valve

Engines 601.91, 602.91, 603.91

The pressure control valve is designed as a diaphragm-type valve and built into the oil separator in the cylinder head cover.

A hole is present in the cylinder head cover to vent the diaphragm chamber in the pressure control valve (arrow). This hole must not be plugged by dirt or preservation agents.

Fig 5: Locating Hole Is Present In Cylinder Head Cover

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Fig 6: Identifying Pressure Control Valve

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Pressure control valve, engines 602.96, 603.96

Turbo-engines with exhaust gas recirculation are also equipped with a pressure control valve (141a). For space reasons this valve is installed in the rear section of the cylinder head cover.