Engine oil circulates within the engine’s passages primarily to provide lubrication, but it also plays a significant role in cooling.
The Role of Oil in Cooling
To briefly discuss cooling, oil absorbs heat from components that do not interact with the coolant. Typically, the coolant draws heat from the cylinders and exhaust pipes in the cylinder head in most engines. The oil helps regulate the temperature of parts such as the crankshaft, camshaft, connecting rods, and pistons.
Materials and Heat Conduction
Generally, the crankcase is constructed from thin sheet metal, contrasting with the cast iron used for the engine’s main components. This sheet metal configuration allows for a faster and more effective transfer of heat from the oil to the surrounding air.
Importance of Oil Pressure
While oil circulates throughout the engine, it must do so not only with a minimal flow but also with adequate pressure. Pressure represents an applied force; in this case, the oil is pushed through the system by the pump, pressing against the walls of the pipes and the moving parts, such as the bearings of the crankshaft and camshaft. This force is crucial in keeping the bearings of the crankshaft, connecting rods, and camshaft separated. Without appropriate pressure, the bearings would come into contact with the rotating components, leading to rapid damage.
How Does Oil Pressure Work?
But how is pressure created? For example, consider a garden hose at home. When you turn it on, water flows out immediately. Why is that? Simply because the pressure in the system is generated by one or more pumps, and when you need to water your garden, there’s no delay in water delivery—it is already there, pushed by the overall pressure of the system.
Comparison with the Engine Oil Circuit
The same principle applies to an engine; the pump draws oil from the bottom of the crankcase and sends it through pipes designed to deliver oil to the components needing lubrication and cooling. The bearings of the crankshaft, camshaft, and other engine parts requiring pressure for proper operation share a common characteristic: the clearance between the moving parts is very minimal, similar to a plug at the pipe’s end.
Limiting Oil Losses
This “plug” effect, which occurs at several points, helps limit significant oil losses. When losses are minimal, the pump can build pressure within the lubrication system. Each bearing has very little free play, which allows for a slight oil escape. This negligible loss does not affect a new engine and allows for the lubrication of components like cylinder walls through oil splashing.
Oil Pressure Check
The engine doesn’t always operate at a constant speed. It makes sense to assume that the pump operates at the engine’s speed. But what regulates the pressure once it peaks at a certain speed? There is a simple valve situated within the oil circuit. This valve remains closed initially, but when the pressure set by the manufacturer is reached, the valve, which is kept closed by a spring, opens and allows some oil to return to the crankcase, thus controlling the pressure.
Situational Analysis: Oil Pressure and Temperature
Let’s consider a scenario: The engine is started, and the pressure rises to around 50 psi. We can reasonably conclude that all oil outlets are blocked and that the engine is in good condition. During warm-up, it is normal for the pressure to decrease due to oil thinning from heat. Choosing the correct oil grade is essential for ensuring the engine remains well-lubricated.
Pressure Drop and Engine Wear
If pressure decreases over time and engine wear occurs, some misguided individuals on internet forums may suggest replacing the wastegate spring with a stronger one. This is incorrect; it will not solve the problem. Low pressure indicates that one of the “plugs” in the pipes is open, either partially or entirely. For instance, bearings on the crankshaft serve as a plug, which is also true for camshaft bearings.
Consequences of Bearing Wear
If one or more bearings become severely worn, they will leak more oil than intended, resulting in lowered pressure. The relief valve will not be able to rectify the situation.
About the author
André Fitzback is a technician and owner of Fitzback Garage Voitures Anciennes. He has passionately studied vintage cars and their original mechanics for over forty years. These models no longer hold many secrets for him. He is enthusiastic about anything powered by gasoline, diesel, or propane that is old!
August 24, 2024 André Fitzback
The Role of Engine Oil in Vehicle Performance
Engine oil circulates inside the engine’s pipes, primarily to lubricate critical components. However, its functions extend beyond lubrication; oil plays a crucial role in cooling various engine parts.
The Role of Oil in Cooling
A quick word on cooling: engine oil picks up heat from parts that are not directly in contact with the coolant. While the coolant absorbs heat from the cylinders and exhaust pipes, oil helps regulate the temperature of components such as the crankshaft, camshaft, connecting rods, and pistons.
Materials and Heat Conduction
The crankcase of an engine is typically made of thin sheet metal, which contrasts with the cast iron construction of the engine block. This sheet metal design allows for efficient heat transfer, expediting the removal of heat from the oil into the surrounding air.
Importance of Oil Pressure
Oil circulation must occur not only at a certain flow rate but also under pressure. In essence, pressure is an applied force necessary for effective lubrication. The oil pump forces the oil to exert pressure against the walls of the oil passages and moving components, such as bearings. Proper pressure helps maintain a safe distance between moving parts, preventing rapid wear and damage.
How Does Oil Pressure Work?
To understand oil pressure, consider the function of a garden hose. When you turn on the tap, the water flows immediately due to the pressure created by one or more pumps upstream. The same principle applies to engine oil. The oil pump draws oil from the crankcase and directs it through a network of pipes to lubricate critical components.
Comparison with the Engine Oil Circuit
In an engine, the oil pump operates continuously as the engine runs, ensuring a steady flow of oil to all necessary parts. The precise tolerances between moving components create fine gaps, akin to a plug at the end of a pipe, which helps minimize oil loss and maintain overall system pressure.
Limiting Oil Losses
These ‘plugs’ (like bearings) help limit oil losses within the lubrication system. When oil loss is minimal, the pump can build adequate pressure. Each bearing allows a small amount of oil to escape, which is acceptable in new engines, as this ensures proper lubrication of cylinder walls through oil projection.
Oil Pressure Check
The engine operates at varying speeds, but the oil pump speed directly correlates with engine RPM. A pressure relief valve in the oil circuit maintains optimal pressure by opening once the pre-established pressure limit is reached, releasing excess oil back into the crankcase.
Situational Analysis: Oil Pressure and Temperature
As the engine starts, pressure will rise to approximately 50 psi; this indicates no blockages and a well-functioning engine. However, as the engine warms up, pressure may drop due to the thinning of the oil. Choosing the correct oil viscosity is vital for effective lubrication under different operating conditions.
Pressure Drop and Engine Wear
Over time, if oil pressure decreases, it can signify potential engine wear. Contrary to popular advice on forums suggesting stronger wastegate springs, a consistent drop in pressure indicates that a “plug” has failed or become compromised, allowing excessive oil to leak.
Consequences of Bearing Wear
When bearings wear excessively, they permit more oil to escape than designed, aggravating the drop in pressure. The relief valve will not adjust pressure adequately in this scenario, leading to potential engine damage if left unaddressed.
Common Causes of Oil Pressure Loss
- Worn bearings causing excessive oil leakage
- Oil pump failure or damage
- Blocked oil passages
- Low oil levels or incorrect oil viscosity
Practical Tips for Preventing Oil Pressure Issues
- Regularly check and change the engine oil according to manufacturer recommendations.
- Monitor oil levels frequently to ensure adequate lubrication.
- Use the correct grade of oil for the engine’s specific needs.
- Perform routine maintenance checks to identify potential issues early.
About the Author
André Fitzback is a technician and owner of the Fitzback Garage Voitures Anciennes workshop. He has been passionately studying old cars and their original mechanics for over forty years. These models no longer hold many secrets for him. Anything that burns gasoline, diesel, or propane and is old, he loves!