Diesel Engine Lubrication System


The lubrication system of a diesel engine is basically the same as that of a gasoline engine. The diesel engine uses a specially-designed oil filter because it generates more carbon particles during combustion than a gasoline engine. The diesel engine also has an oil cooler to maintain the oil’s lubrication performance because the combustion temperature and combustion pressure is higher than that of a gasoline engine.

1. Oil Cooler

Most oil coolers are the water-cooled type, and are installed on the front or side of the engine, or under the radiator. The oil, which is drawn from the oil pan through the oil filter by the oil pump, is provided to each part where friction occurs after being cooled at the oil cooler. To prevent oil cooler damage, a relief valve is installed.

2. Oil Nozzle

In many diesel engines, oil nozzles are provided in the cylinder block to cool the pistons. Part of the lubrication oil pumping from the main oil gallery in the cylinder block passes through the check valve and is injected from the oil nozzle to cool the inside of the piston. The check ball closes the oil passage by the spring force when the oil pressure drops below approx. 14kPa (1.4 kgf/cm2). This is to prevent the oil pressure in the lubrication circuitry from dropping too low by closing the oil passage.


Two Types of Check Valve

There are two types of check valves used for the diesel engine.

1.One type uses a single check valve for all the oil nozzles.

2.The other type uses one check valve for each individual oil nozzle.

Diesel Engine Cooling System

The cooling system of the diesel engine is basically the same as that of the gasoline engine. However as the heat efficiency rate is better, the coolant temperature is slower to rise. Thus, some for the cold area specification engines have an auxiliary heater.

1HD-FTE engine viscous type power heater:

When the idle up switch is turned on, the drive belt drives the power heater, and the internal silicon oil is stirred up to generate the heat. This heat generation warms the coolant.


Here are some other types of auxiliary



Electrical type power heater

Combustion type power heater

PTC (Positive Temperature Coefficient) heater etc.

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