TM 5-3805-258-24-1L U B R I C A T I O N S Y S T E MT E S T I N G A N D A D J U S T I N Gmum permissible pressure from the ENGINEOIL PRESSURE CHART. If the pressurereading on the test gauge is below the minimumpermissible pressure, find the cause and correctit. Operation of the engine with low oil pressurecan be the cause of engine failure or of a reduc-tion in engine life.Crankcase Oil LevelCheck the level of the oil in the crankcase. Add oilif needed. It is possible for the oil level to be too farbelow the oil pump supply tube. This will cause theoil pump to not have the ability to supply enoughlubrication to the engine components.Oil Pump Does Not Work CorrectlyThe inlet screen of the supply tube for the oil pumpcan have a restriction. This will cause cavitation (thesudden making of low pressure bubbles in liquids bymechanical forces) and a loss of oil pressure. Airleakage in the supply side of the oil pump will alsocause cavitation and loss of oil pressure. If the bypassvalve for the oil pump is held in the open (unseated)position, the lubrication system can not get to maxi-mum pressure. Oil pump gears that have too muchwear will cause a reduction in oil pressure.Oil Filter and Oil Cooler Bypass ValvesIf the bypass valve for the oil filter or oil cooler isheld in the open position (unseated) and the oil filteror oil cooler has a restriction, a reduction in oil pres-sure can be the result. To correct this problem, installa new Caterpillar oil filter.Too Much Clearance at Engine Bearings OrO p e n(Broken or Disconnected Oil Line or Passage)Lubrication SystemComponents that are worn and have too muchbearing clearance can cause oil pressure to be low.Low oil pressure can also be caused by an oil line oroil passage that is open, broken or disconnected.Oil CoolerLook for a restriction in the oil passages of the oilcooler. If the oil cooler has a restriction, the oil tem-perature will be higher than normal when the engineis running. The oil pressure of the engine will not getlow just because the oil cooler has a restriction.OIL PRESSURE IS HIGHOil pressure will be high if the bypass valve for theoil pump can not move from the closed position.TOO MUCH BEARING WEARWhen some components of the engine show bear-ing wear in a short time, the cause can be a restrictionin an oil passage. A broken oil passage can also be thecause.If the gauge for oil pressure shows enough good oilpressure, but a component is worn because it is notgetting enough lubrication, look at the passage for oilsupply to that component. A restriction in a supplypassage will not let enough lubrication get to a com-ponent and this will cause early wear.4-30
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