D 250 Pickup L6-359 5.9L DSL (1992)
Oil Cooler: Description and Operation
Fig. 7 Lubrication System Components & Flow
The lubricating gerotor type pump draws oil from the pan and forces it through the lubrication system. The pressure regulation valve controls the oil
pressure in the system. This valve is designed to keep the oil pressure from exceeding 60 psi. When the oil pressure is greater than 60 psi, the valve
opens uncovering the dump port so part of the oil is routed to the oil pan. The filter bypass valve ensures a supply of oil in the event the filter becomes
plugged. The bypass valve, located on oil cooler cover, will let the oil flow bypass a plugged filter. The valve is designed to open when the pressure drop
across the filter is more than 20 psi, as with a plugged filter. The piston pins are lubricated by the splash from the piston cooling nozzles. The oil pump
idler gear bushing is pressure lubricated. The remainder of the front gear train is lubricated by oil carry over and splash.
The oil coolers are full flow, plate type cooler. The oil flows through a cast passage in the cooler cover and through the element where it is cooled by
engine coolant flowing past the plates of the element. After the oil is cooled, it flows through the filter. From the filter oil flows to the turbocharger and
engine.
The turbocharger receives cooled and pressurized oil through a supply line from the filter head. A drain line connected to the bottom of the turbocharger
housing returns the oil to the oil pan.
