C9.3 Tier 4 Final Engines Lubrication System Caterpillar


Lubrication System
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1.1. References
2.1. System Operation

References

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Illustration 1g06301698

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System Operation



Illustration 2g01950413
Lubrication system schematic
(1) Passage to the rocker arms
(2) Cylinder head gallery
(3) Passage to pushrod lifters
(4) Piston cooling jets
(5) Oil supply line for the fuel pump
(6) Oil supply line for the air compressor
(7) Main bearings
(8) Camshaft bearings
(9) Main oil gallery
(10) Turbocharger oil supply line
(11) Supply for the number 4 main bearing
(12) Passage to camshaft idler gear bearing
(13) Oil filter bypass valve
(14) Passage
(15) Oil cooler bypass valve
(16) Engine oil filter
(17) Engine oil cooler
(18) Auxiliary engine oil filter (if equipped)
(19) Engine oil pump
(20) Oil pump bypass valve
(21) Engine oil pan

Engine oil pump (19) is mounted to the bottom of the cylinder block inside the engine oil pan (21). The engine oil pump (19) pulls oil from engine oil pan (21). The engine oil pump pushes the oil through the passage to the engine oil cooler (17). Oil then flows through engine oil filter (16). The filtered oil then enters the supply for the number 4 main bearing (11), turbocharger oil supply line (10), and main oil gallery (9). The supply for the number 4 main bearing (11) supplies oil to the number four camshaft bearing.

The main oil gallery (9) distributes oil to main bearings (7), piston cooling jets (4), and camshaft bearings (8). Oil from main oil gallery (9) exits the front of the block. The oil then enters a groove that is cast in the front housing.

Oil enters the crankshaft through holes in the bearing surfaces (journals) for the main bearing (7). Passages connect the bearing surface (journal) for the main bearing (7) with the bearing surface (journal) for the connecting rod.

Oil supplied from the main oil gallery (9) is directed to cylinder head gallery (2) and through passage (1) to the rocker arm mechanism. Also, the oil is supplied to the oil supply line for the fuel pump (5) and oil supply line for the air compressor (6).

Oil from the front main bearing enters a passage (12) to the camshaft idler gear bearing. Oil passages in the crankshaft send oil from all the main bearings (7) through the connecting rods to the connecting rod bearings.

The passages send oil from the camshaft bearings (8) to an oil passage in the side covers. The oil then enters a hole in the shafts to pushrod lifters (3). The oil lubricates the bearings of the lifter.

Note: Engines that are equipped with an auxiliary oil filter (18) will receive oil at a port. The filtered oil will be returned to engine oil pan (21).

The oil circuit consists of a common pressure circuit. The pressure circuit typically operates at a pressure of 240 kPa (35 psi) to 480 kPa (70 psi). The pressure circuit provides engine oil that has been filtered to the lubricating system of the engine. Oil is drawn from the engine oil pan (21). Oil is supplied through the engine oil cooler (17) and engine oil filter (16) to the engine.

After the lubrication oils work is done, the lubrication oil returns to the engine oil pan.

The oil pump bypass valve (20) limits the pressure of the oil that is coming from the engine oil pump (19). The engine oil pump (19) can pump more than enough oil into the system. When there is more than enough oil, the oil pressure increases. When the oil pressure increases, the oil pump bypass valve (20) will open. This opening allows the oil that is not needed to go back to the suction side of the engine oil pump (19).

The bypass valves (13) and (15) will open when the engine is cold (starting conditions). Opening the bypass valves achieves immediate lubrication of all components. Immediate lubrication is critical when high viscosity cold oil causes restrictions in oil flow through engine oil cooler (17) and engine oil filter (16). The engine oil pump (19) sends the cold oil through the bypass valves around the engine oil cooler (17) and engine oil filter (16). This bypass allows supplies oil directly to the turbocharger oil supply line (10) and the main oil gallery (9) in the cylinder block.

When the oil gets warm, the pressure difference in the bypass valves decreases and the bypass valves close. After the bypass valves close, there is a normal flow of oil through the engine oil cooler and the engine oil filter.

The bypass valves will also open when there is a restriction in the engine oil cooler (17) or engine oil filter (16). This design allows the engine to be lubricated even though engine oil cooler (17) or engine oil filter (16) are restricted.

The engine oil cooler bypass valve is also activated by pressure. If the oil pressure differential across the engine oil cooler reaches 125 ± 30 kPa (18 ± 4.5 psi), the valve will open. Opening the valve allows the oil flow to bypass the engine oil cooler (17).

The main oil flow now reaches the main engine oil filter (16). When the oil pressure differential across the oil filter bypass valve (12) reaches 125 ± 30 kPa (18 ± 4.5 psi), the valve opens in order to allow the oil flow to go around the oil filter (16). The oil flow continues in order to lubricate the engine components. When the oil is cold, an oil pressure difference in the bypass valve also causes the valve to open. This bypass valve provides immediate lubrication to all engine components when high viscosity cold oil causes a restriction in oil flow through filter (16). The bypass valve will also open when there is a restriction in the engine oil filter (16). This design allows the engine to be lubricated even though engine oil filter (16) is restricted.

Note: Refer to Specifications, "Engine Oil Filter Base".

Filtered oil flows through the main oil gallery (9) in the cylinder block. Oil is supplied from the main oil gallery (9) to the following components:

  • Piston cooling jets

  • Valve mechanism

  • Camshaft bearings

  • Crankshaft main bearings

An oil cooling chamber is formed by the following two items: the lip forged at the top of the piston skirt and the cavity behind the ring grooves in the crown. Oil flow for the piston cooling jet enters the cooling chamber through a drilled passage in the skirt. Oil flow from the piston cooling jet returns to the engine oil pan (21) through the clearance gap between the crown and the skirt. Four holes that are drilled from the piston oil ring groove to the interior of the piston drain excess oil from the oil ring.

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