Toyota 3S-GE Repair Manual page 390

EG-376
ENGINE -— LUBRICATION SYSTEM
OIL
OIL
OIL
A pressure feeding lubrication system has been adopted to supply oil to the moving parts of this
engine. The lubrication system consists of an oil pan, oil pump, oil filter and other external parts
which supply oil to the moving parts in the engine block. The oil circuit is shown in the illustration
at the top of the previous page. Oil from the oil pan is pumped up by the oil pump. After it passes
through the oil filter, it is fed through the various oil holes in the crankshaft and cylinder block.
After passing through the cylinder block and performing its lubricating function, the oil is
returned by gravity to the oil pan. A dipstick on the center left side of the cylinder block is
provided to check the oil level.
PUMP
The oil pump pumps up oil from the oil pan and feeds it under pressure to the various parts of the
engine. An oil strainer is mounted in front of the inlet to the oil pump to remove impurities. The
oil pump itself is a trochoid type pump, inside of which is a drive rotor and a driven rotor. When
the drive rotor rotates, the driven rotor rotates in the same direction, and since the axis of the
drive rotor shaft is different from the center of the driven rotor, the space between the 2 rotors
changes as they rotate. Oil is drawn in when the space widens and discharged when the space
becomes narrow.
PRESSURE REGULATOR (RELIEF VALVE)
At high engine speeds, the engine oil supplied by the oil pump exceeds the capacity of the engine
to utilize it. For that reason, the oil pressure regulator works to prevent an oversupply of oil.
During normal oil supply, a coil spring and valve keep the bypass closed, but when too much oil
is being fed, the pressure becomes extremely high, overpowering the force of the spring and
opening the valves. This allows the excess oil to flow through the valve and return to the oil pan.
FILTER
The oil filter is a full flow type filter with a relief valve built into the paper filter element. Particles
of metal from wear, airborne dirt, carbon and other impurities can get into the oil during use and
could cause accelerated wear or seizing if allowed to circulate through the engine. The oil filter,
integrated into the oil line, removes these impurities as the oil passes through it. The filter is
mounted outside the engine to simplify replacement of the filter element. A relief valve is also
included ahead of the filter element to relieve the high oil pressure in case the filter element
becomes clogged with impurities. The relief valve opens when the oil pressure overpowers the
force of the spring. Oil passing through the relief valve bypasses the oil filter and flows directly
into the main oil hole in the engine.