FUSO 4M4 – LUBRICATION – STRUCTURE AND OPERATION – Oil Cooler and Oil Filter

Bypass valve
โ€ข When the engine oil is cool and its viscosity is high, or when the oil cooler element becomes clogged and restricts the flow of the engine oil, the bypass valve opens to let the engine oil bypass the oil cooler and flow directly to the oil filter.

Regulator valve
โ€ข When the oil pressure in the main oil gallery exceeds the specified level, the regulator valve opens to adjust the oil pressure by allowing part of the engine oil to escape to the oil pan.