D439E Service Manual 2. Engine Mechanical System (D439E)
102
Oil Cooler
Oil cooler is equipment for heat exchange between
the coolant and oil fed from the crankcase water
jacket and oil pump, respectively. The oil cooler has
a bypass valve that opens when the element (1)
becomes clogged.
Bypass Valve
When the oil viscosity is high (in cold) or oil path
shows high resistance depending on the element
load, the bypass valve (1) opens and oil goes
directly to oil filter without passing oil cooler.
Regulator Valve
When oil pressure in main oil gallery exceeds the
specification, regulator valve (1) opens and some
engine oil drains to the oil pan to adjust the oil
pressure.
Oil Pressure Switch
If the pressure of engine oil which is sent to the main
oil gallery is below the specification, the built-in relay
in the oil pressure switch (1) is closed, then the
warning lamp in the instrument panel is on to inform
the driver of abnormal pressure.
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