BMW N73B60 - Oil Pump and Pressure Control; Oil Pump Description; Pressure Control Explanation

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N73B60 Engine - Diagnosis
Oil Pump
The oil pump is mounted at an angle to the crankshaft bearing cap and is driven by the
crankshaft using a roller chain. The oil pump is a two-stage gear oil pump with two gear
clusters.
1. Mounting points
2. Oil pump drive shaft
3. Oil pressure from pump to engine
4. Control valve (Pump Stage/Pressure
Control)
5. Oil pressure control tube from the
engine to the control valve.
6. Oil pickup strainer
7. Pressure relief valve (over 15 Bar)
8. Oil filter
Pressure Control
The oil pressure control valve in the oil pump has two functions:
1. Deactivates stage two oil pump circuit above 2 bar. Stage two is only active in the
lower speed range. This is to ensure that there is always sufficient oil pressure for
the VANOS units even at high oil temperatures and low speeds. The oil pump power
consumption is reduced by deactivating stage two.
2. Monitoring the required oil pressure for the engine. The piston in the control valve is
moved by a spring against the engine control pressure which is returning from the
engine. This means that precise monitoring of the actual engine oil pressure is pos-
sible.
AA sseeppaarraattee pprreessssuurree rreelliieeff vvaallvvee iinn tthhee ooiill ppuummpp aauuttoommaattiiccaallllyy ooppeennss aatt tthhee mmaaxxiimmuumm pprreess--
ssuurree ooff aapppprrooxxiimmaatteellyy 1155 bbaarr.. TThhiiss pprreevveennttss ddaammaaggee iinn tthhee ooiill ppuummpp eessppeecciiaallllyy aatt llooww ooiill
tteemmppeerraattuurreess..
• Disassemble oil pump for visual inspection.
KT-9614
Oil Pump