TM 5-3825-226-245P6225 HYDRAULIC TEST BOXCrankcase Oil LevelCheck the level of the oil in the crankcase. Addoil if needed. It is possible for the oil level to be too farbelow the oil pump supply tube. This will result in the oilpump not having the ability to supply enough lubricationto the engine components.Oil Pump Does Not Work CorrectyThe inlet screen of the supply tube for the oilpump can have a restriction. This will result incavitation and a loss of oil pressure. Air leakage in thesupply side of the oil pump will also cause cavitationand loss of oil pressure. If the pressure regulating valvefor the system is held in the open (unseated) position,the lubrication system can not get to maximumpressure. Oil pump gears that have too much wear willcause a reduction in oil pressure.Oil Filter and Oil CoolerA dirty oil filter will cause a reduction in oilpressure. When the oil filter is filled with dirt, arestriction of oil flow thru the filter and a reduction offiltered oil pressure is the result.The bypass valve will cause the flow of oil to goaround the filter elements when there is a reduction tothe flow through the elements. When the bypass valveis open, oil that is not filtered is permitted to flow thruthe engine. To correct this problem, install a newCaterpillar filter.Look for a restriction in the oil passages of theoil cooler. If the oil cooler has a restriction, the oilcooler bypass valve in the oil filter base will open. Thiswill cause the flow of oil to go around the oil cooler. Theoil temperature will be higher than normal when theengine is running. The oil pressure of the engine willbecome low if the oil cooler has a restriction.Too Much Clearance at Engine Bearings or Open,Broken or Disconnected Oil Line or Passage inLubrication SystemComponents that are worn and have too muchbearing clearance can cause oil pressure to be low. Lowoil pressure can also be caused by an oil line or oilpassage that is open, broken or disconnected.OIL PRESSURE IS HIGHOil pressure will be high if the bypass valve forthe oil pump can not move from the closed position.TOO MUCH COMPONENT WEARWhen some components of the engine showbearing wear in a short time, the cause can be arestriction in the oil passage. A broken oil passage canalso be the cause.If the gauge for oil pressure shows the correctoil pressure, 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 acomponent and this will cause early wear.2-68
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