Mercedes-Benz OM 471 Introduction Into Service Manual page 193

System components
Front side, without drive gear (9)
1 Oil pump
3 Oil strainer
5 Oil intake manifold
6 Suction pipe
8 Pressure line
12 Safety valve
14 Oil duct (to pressure regulator valve
(10))
15 Impeller
Function
The drive gear (9) for the oil pump (1) which is driven by the
crankshaft gear drives the two impellers (15).
The rotational movement of the impellers (15) and the design of
the pump chamber cause the engine oil to be suctioned up and
delivered to the oil outlet (13) along the inner wall of the pump.
When sucked in, the engine oil in the oil pan (2) flows first to the
oil strainer (3) and the suction line (6), before passing through the
oil inlet (11) into the oil pump (1).
The engine oil flows first through the oil outlet (13) into the
pressure line (8) before then flowing through the return flow
check valve (7) and the main oil duct's feed line into the engine oil
circuit.
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Regulation of the engine oil pressure takes place via the pressure
regulator valve (10).
The pressure regulator valve (10) has the oil pressure applied to it
via the engine oil in the oil duct (14) which is connected with the
main oil duct. A certain amount of engine oil is fed via the
pressure regulator valve (10) on the suction line according to the
oil pressure in the oil duct (14). This regulates the engine oil
pressure on the one hand and reduces the operating energy input
of the oil pump (1) on the other.
Impermissibly high pressures in the oil circuit are avoided via the
safety valve (12) which can occur in the cold start phase of the
engine if the engine oil is not yet viscous.
The safety valve (12) opens at a pressure >10 bar and routes some
of the engine oil back into oil pan (2).
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