D330, D333, 3304, 3306 – Lubrication System

The arrows show the approximate direction of oil flow in the engine. 1. Oil filter base (includes bypass valves). 2. Engine oil cooler. 3. Turbocharger oil reservoir in center section. 4. Oil passage through rocker arm shaft. 5. Oil cooler bypass valve. 6. Timing gears (in front compartment). 7. Oil pump (in front part of oil pan). 8. Oil filter case. 9. Oil pan (sump). 10. Oil filter bypass valve. 11. Oil manifold (in cylinder block assembly).

The lubrication system consists of a sump (oil pan), oil pump, oil cooler and oil filter. The cylinder block contains an oil manifold and oil passages to direct the oil to the various parts.

The pump draws oil from the sump and forces the oil through the oil cooler, oil filter, and into the oil manifold. Oil flows through connecting passages to the external and internal engine parts. A regulating valve in the pump body controls the maximum pressure of the oil from the pump.

When the engine is started, the lubricating oil in the oil pan is cold (cool). This cool viscous oil does not flow readily through the system. This cool oil forces bypass valves, in the oil cooler to open, and allows an unrestricted oil flow through the engine.

As the temperature of the oil increases, the viscosity and pressure of the oil decreases, and the bypass valves close. Now, only filtered oil is delivered to the engine parts.

A dirty or clogged oil filter element will not prevent lubricating oil from being delivered to the engine parts. The oil filter bypass valve will open, allowing oil to bypass the element.

The oil manifold directs lubricant to the main bearing supply passages, timing gear bearings, to a passage leading through the cylinder head to the valve rocker arm shaft, and the rocker arms and valves.

Oil spray orifices in the engine block, near the crankshaft main bearings, spray oil on the underside of the pistons. This cools the pistons and provides lubricant for the piston pins, cylinder walls and piston rings.

The connecting rod bearings receive oil through drilled passages in the crankshaft, between the main bearing journals and connecting rod journals.

Oil draining from the valve rocker arms lubricates the valves, push rods and lifters. On six cylinder engines, the camshaft cams, and the camshaft intermediate and rear bearings, are splash lubricated. On four cylinder engines, the camshaft cams are splash lubricated and the camshaft bearings are pressure lubricated.

All timing gear bearings, except the accessory drive gear bearing, are pressure lubricated. Oil is supplied to the bearings through passages in the cylinder block. The accessory drive gear bearing is lubricated by oil draining from the accessory drive shaft housing.

When the engine is warm, and running at rated speed, the oil pressure gauge should register in the “operating range.” A lower pressure reading is normal at idling speeds.

A small orifice in the gauge connection prevents rapid gauge fluctuation. Check this orifice for dirt if the gauge becomes inoperative.

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