The Engine Lubrication System:
The life of an engine largely depends on its lubricating and cooling systems. Without a proper supply of oil or the ability to dissipate high temperatures, an engine will be quickly destroyed. The lubricating system plays a vital role in engine longevity, performing several important functions that keep the engine operating smoothly and efficiently. The engine lubrication system is a complex but essential network of components working together to protect the engine from wear, heat and contamination. From the oil pump that circulates oil through the system to the filter that removes harmful particles, each component serves a specific purpose in maintaining engine health. Understanding how these components work together helps in recognizing the importance of regular maintenance and oil changes. Without proper lubrication, even the most well-built engine would fail prematurely, highlighting the critical role this system plays in overall engine longevity and performance.
Role of the Lubrication System:
The engine's lubricating system does more than simply reduce friction. It holds an adequate supply of oil to cool, clean, lubricate, and seal the engine. The system also removes contaminants from the oil and delivers oil to all necessary areas throughout the engine. This multi-functional approach ensures that engine components receive proper protection under various operating conditions.
Engine Oil:
Engine oil is specially formulated to lubricate and cool engine parts. The moving components of an engine are fed a constant supply of oil, which is stored in the oil pan or sump. The oil pump draws the oil from the sump and passes it through a filter where dirt and other contaminants are removed. After filtration, the oil is moved throughout the engine via oil passages or galleries. Following circulation through the engine, the oil returns to the sump, completing the continuous cycle.The Oil Pump:
The oil pump serves as the heart of the lubricating system. Just as the human heart circulates blood through veins, an engine's oil pump circulates oil through passages in the engine. The oil pump pickup consists of a line that runs from the oil pump to the oil stored in the oil pan. This pickup usually contains a filter screen that remains submerged in the oil at all times. The screen serves to keep large particles from reaching the oil pump and should be cleaned any time the oil pan is removed. In some designs, the pickup may contain a by-pass valve that allows oil to enter the pump if the screen becomes totally plugged. Because the oil pump operates as a positive displacement pump, an oil pressure relief valve is necessary to prevent excessively high system pressures from occurring as engine speed increases. Once oil pressure exceeds a preset limit, the spring-loaded pressure relief valve opens and allows the excess oil to bypass the rest of the system and return directly to the sump.The Oil Pan or Sump:
The oil pan attaches to the bottom of the engine block and serves as the reservoir for the engine's oil. It is designed to hold the amount of oil needed to lubricate the engine when running, plus a reserve. The oil pan also helps to cool the oil through its contact with outside air. Oil is drawn out by the pump, pressurized, and sent to the main oil gallery where it is channeled off to bearing surfaces and the valve train. After use, the oil drains back into the pan, maintaining a continuous flow throughout the engine. This configuration is commonly referred to as a wet sump oil system because the sump always contains oil.
Pan Baffles:
In a wet sump system, oil can slosh around during hard cornering or braking. During these maneuvers, oil may move away from the oil pump's pickup, causing a temporary halt in oil flow through the engine, which can lead to destruction. Sloshing also affects the rotation of the crankshaft; as the crankshaft rotates through a thick puddle of oil, it meets resistance and slows down. To help prevent sloshing, many engines incorporate baffles in the oil pan to limit oil movement.Dry Sump Systems:
To eliminate the possibility of oil sloshing, some OEM engines are fitted with a dry sump oil system, as are most race engines. In a dry sump system, the oil pan does not store oil. Instead, the dry oil pan merely seals the bottom of the crankcase, and the oil reservoir is a remote container set apart from the engine. Rather than having a single path for oil travel, dry sump pumps can feed oil directly to the crankshaft, valve train, and turbocharger. Normally one external oil pump is used; however, some systems employ two pumps. The second pump pulls all the oil out of the sump and returns it to the reservoir while also lowering the pressure inside the crankcase. Dry sump systems provide immediate oil delivery to critical areas of the engine and prevent oil starvation caused by acceleration, braking, and cornering forces. Because the dry sump is smaller than a wet sump, the engine can be placed lower in the frame to improve overall vehicle handling.
The Oil Filter:
All oil that leaves the oil pump is directed to an oil filter. This ensures that small particles of dirt and metal suspended in the oil will not reach the close-fitting engine parts. Filtering stops these impurities, which can cause premature wear, from circulating through the engine while also increasing the usable life of the oil.The filter assembly threads directly onto the main oil gallery tube. Oil from the pump enters the filter and passes through the filter element, then flows back into the engine's main oil gallery. A typical oil filter assembly is a disposable metal container filled with specially treated paper or other filter substances such as cotton or felt. Some engines feature a separate cartridge that fits into a metal casing. The filter is usually mounted on and sealed to an adapter bolted to the block, though it may also be attached to the timing cover or remotely mounted with oil lines connecting the filter to the oil galleries in the block. Some oil filters incorporate an antidrainback valve. This valve prevents oil drainage from the filter when the engine is not running, allowing for a supply of filtered oil as soon as the engine is started and oil pressure builds. The oil filtration system used on today's vehicles is commonly referred to as a full-flow system, meaning all oil going to the engine bearings passes through the filter first. However, should the filter become plugged, a relief valve in the filter will open and allow oil to bypass and go directly to the bearings. This provides the bearings and the rest of the engine with necessary, though unfiltered, lubrication.
Oil Coolers:
To control oil temperature, many diesel, high-performance, and turbocharged engines have an external engine oil cooler. Oil flows from the pump through the cooler and then to the engine. An oil cooler looks like a small radiator mounted near the front of the engine or within the radiator. Heat is removed from the oil as engine coolant flows through or around the cooler and air passes through it. This cooling function is important because hot oil mixed with oxygen breaks down and forms carbon and varnish. The higher the temperature, the faster these deposits build. An oil cooler helps maintain the oil at its normal operating temperature.Engine Oil Passages or Galleries:
From the filter, oil flows into the engine oil galleries. These galleries consist of interconnecting passages that have been drilled completely through the engine block during manufacturing. The outside ends of the passages are blocked off so oil can be routed through these galleries to various parts of the engine. The crankshaft also contains oil passages to route oil from the main bearings to the connecting rod bearing surfaces. Engines with a remote oil filter, an oil cooler, or a dry sump system have external oil lines that move the oil to designated areas.
Oil Seals and Gaskets:
Seals and gaskets are used throughout the engine to prevent both external and internal oil leaks. The most common materials used for sealing are synthetic rubber, soft plastics, fiber, and cork. In critical areas, these materials might be bonded to metal for enhanced durability and effectiveness.Monitoring Oil Level and Pressure:
Dipstick:
The dipstick is the primary tool used to measure the level of oil in the oil pan. The end of the stick is marked to indicate when the engine oil level is correct. It also features a mark to indicate the need to add oil to the system.Oil Pressure Indicators:
All vehicles have an oil pressure gauge and/or a low-pressure indicator light. Oil gauges are either mechanically or electrically operated and display the actual oil pressure of the engine. The indicator light only warns the driver of low oil pressure. In a mechanical gauge, oil travels to the back of the gauge where a springy, flexible, hollow tube called a Bourdon tube uncoils as pressure increases. A needle attached to the Bourdon tube moves over a scale to indicate the oil pressure. Most pressure gauges, however, are electrically controlled. An oil pressure sensor or sending unit is screwed into an oil gallery. As oil passes through the sender, it moves a diaphragm connected to a variable resistor. This resistor changes the amount of current passing through the circuit. A gauge on the dashboard reacts to the current and moves a needle over a scale to indicate oil pressure, or the current is translated into a digital reading on the gauge.Warning light systems are simpler electrical circuits. The indicator light comes on when the circuit is completed by a sensor. This sensor has a diaphragm connected to a switch inside the sensor. Under normal conditions, the sender switch remains open. When oil pressure falls below a certain level, the reduction of pressure causes the diaphragm to move and close the sender switch, completing the electrical circuit. When this happens, electricity flows and turns on the warning light on the dashboard.
Electronic Oil Level Indicators:
Some late model vehicles are equipped with an electronic oil level indicator. When the oil level in the oil pan drops below a predetermined level, a sensor completes the warning lamp circuit and the lamp lights, alerting the driver to the need for oil.
How lubrication system work?
The lubrication system operates as a closed loop cycle, beginning with the engine oil stored in the reservoir either the oil pan in a wet sump system or a remote external container in a dry sump system. The process is driven by the oil pump, which acts as the heart of the system. The pump draws oil from the sump through a pickup tube. This pickup is fitted with a filter screen that remains submerged in the oil to catch large debris. Should this screen become totally plugged, a built in by pass valve allows oil to still enter the pump to prevent starvation. Once the pump pressurizes the oil, the system must manage that pressure. Because the pump is a positive displacement type, a spring loaded pressure relief valve opens when pressure exceeds a preset limit, allowing excess oil to bypass the rest of the system and return directly to the sump. From the pump, all pressurized oil is directed to the oil filter in what is known as a full flow system. The filter removes small particles of dirt and metal to prevent premature wear. However, if the filter becomes plugged, its internal relief valve opens to allow unfiltered oil to bypass directly to the engine bearings, ensuring lubrication continues even if filtration temporarily stops. In many diesel, high-performance, and turbocharged engines, the oil is then routed through an external oil cooler. This small radiator removes heat via engine coolant and airflow, keeping the oil at its normal operating temperature to prevent it from breaking down and forming carbon and varnish.The filtered and possibly cooled oil then flows into the engine’s main oil galleries interconnecting passages drilled through the engine block. From these galleries, the oil is channeled off to all critical areas simultaneously: it reaches the bearing surfaces, the valve train, and also travels through oilways inside the crankshaft to reach the connecting rod bearing surfaces. Engines with external components have dedicated external oil lines to move oil to these designated areas. After circulating through and lubricating these moving parts, the oil drains back down by gravity into the sump. In a wet sump system, baffles are used to limit oil sloshing during hard cornering or braking, preventing the oil from moving away from the pickup. In a dry sump system, the pan does not store oil but merely seals the crankcase. A second external pump actively pulls all the oil out of the sump and returns it to the remote reservoir, while also lowering the pressure inside the crankcase. Throughout this entire cycle, the system relies on seals and gaskets made of synthetic rubber, fiber, and cork to prevent internal and external leaks. Finally, the driver monitors the system via the dipstick to check the reservoir level and via an oil pressure gauge or low-pressure warning light, which alerts the driver if pressure drops below safe limits. This continuous, uninterrupted flow of oil is what protects the engine from destruction caused by friction and heat.
0 Comments