Oil pressure: Difference between revisions
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{{wikify|October 2006}} |
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[[File:Murphy oil pressure switch gauges.jpeg|thumb|right|Murphy oil [[pressure gauge]]s with switches that activate on low pressure]] |
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| ⚫ | '''Oil pressure''' is an important factor in the longevity of most [[internal combustion engine]]s. With a forced [[lubrication]] system (invented by [[Frederick Lanchester]]), oil is picked up by a positive displacement [[Oil pump (internal combustion engine)|oil pump]] and forced through oil galleries (passageways) into [[Bearing (mechanical)|bearings]], such as the [[main bearing]]s, [[Crankpin#Big end bearings|big end bearings]] and [[camshaft]] bearings or [[balance shaft]] bearings. Other components such as cam lobes and cylinder walls are lubricated by oil jets. |
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| ⚫ | Sufficient oil pressure ensures that the metal of the rotating shaft (journal) and the bearing shell can never touch, and wear is therefore confined to initial start-up and shutdown. The oil pressure, combined with the rotation of the shaft, also hydrodynamically centers the journal in its shell and cools the bearings. Such a bearing is known as a fluid bearing. |
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| ⚫ | Oil pressure is an important factor in the longevity of most [[internal combustion engine]]s. |
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Oil pressure is higher when the engine is cold due to the increased [[viscosity]] of the oil, and also increases with engine speed until the relief valve in the oil pump opens to divert excess flow. Oil pressure is lowest under hot idling conditions, and the minimum pressure allowed by the manufacturer's tolerances is usually given at this point. Excessive oil pressure may indicate a blocked filter, blocked oil gallery or the wrong grade of oil. Low oil pressure indicates worn bearings or a broken oil pump. |
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Some vehicle engines have an oil [[pressure switch]] that switches a warning light on at low oil pressure. Some vehicles have an [[Pressure measurement|oil pressure gauge]] in the [[dashboard]] or instrument cluster. |
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As bearing clearance increases due to wear and the oil pump declines in efficiency with age, oil pressure falls. Eventually it may be insufficient to protect the bearings, especially if the engine is "lugged" at low rpm. Some engines include an oil pressure gauge which shows the pressure at any given time, while others just employ a warning light which shows when the pressure is insufficient. The sensor for either type is usually mounted near the [[oil filter]] of the engine, just after the oil pump. |
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Oil pressure is |
Oil pressure is created by a fluid flow restriction in the outlet line of the pump, not by the pump itself. Examples of such restrictions include big end and main bearings, as well as camshaft and rocker gear if fitted. |
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== See also == |
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Excessive oil pressure may indicate a blocked filter, blocked oil gallery or the wrong grade of oil. |
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* [[Splash lubrication]], a rudimentary "non-pressurized" form of lubrication found in early engines |
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==External links== |
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* [http://www.aa1car.com/library/us1097.htm Troubleshooting Low Oil Pressure from AA1Car] |
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[[Category:Engine lubrication systems]] |
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[[Category:Engine technology]] |
[[Category:Engine technology]] |
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Latest revision as of 14:03, 8 October 2022
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Oil pressure is an important factor in the longevity of most internal combustion engines. With a forced lubrication system (invented by Frederick Lanchester), oil is picked up by a positive displacement oil pump and forced through oil galleries (passageways) into bearings, such as the main bearings, big end bearings and camshaft bearings or balance shaft bearings. Other components such as cam lobes and cylinder walls are lubricated by oil jets.
Sufficient oil pressure ensures that the metal of the rotating shaft (journal) and the bearing shell can never touch, and wear is therefore confined to initial start-up and shutdown. The oil pressure, combined with the rotation of the shaft, also hydrodynamically centers the journal in its shell and cools the bearings. Such a bearing is known as a fluid bearing.
Oil pressure is higher when the engine is cold due to the increased viscosity of the oil, and also increases with engine speed until the relief valve in the oil pump opens to divert excess flow. Oil pressure is lowest under hot idling conditions, and the minimum pressure allowed by the manufacturer's tolerances is usually given at this point. Excessive oil pressure may indicate a blocked filter, blocked oil gallery or the wrong grade of oil. Low oil pressure indicates worn bearings or a broken oil pump.
Some vehicle engines have an oil pressure switch that switches a warning light on at low oil pressure. Some vehicles have an oil pressure gauge in the dashboard or instrument cluster.
Oil pressure is created by a fluid flow restriction in the outlet line of the pump, not by the pump itself. Examples of such restrictions include big end and main bearings, as well as camshaft and rocker gear if fitted.
See also
[edit]- Splash lubrication, a rudimentary "non-pressurized" form of lubrication found in early engines