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TOPIC: High Oil Pressure

High Oil Pressure 1 year 3 months ago #507

  • STEVE ELLS
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One more thing that I neglected to mention. Oil pressure can be used to determine how much wear has taken place inside the engine. The best place to observe this is at idling oil pressure when the engine is hot (after flying.)
I would recommend that you ask your mechanic to install his gauge on your oil pressure line and check your idling oil pressure. Put a mark on the OP gauge face. When you see your idling oil pressure drop below that mark it's a sign that there's significant wear in your engine--wear only an overhaul will eliminate.
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High Oil Pressure 1 year 3 months ago #505

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Hi, Your 1975 Cessna 172 has a direct reading oil pressure gauge. In other words oil under pressure is tapped at the engine and routed directly to the back of the gauge through a small tube. This type of gauge is referred to as a Bourdon-type gauge. To the best of my knowledge there is no adjustment. One option is to remove the gauge and send it to a company such as Air Parts of Lock Haven for rebuilding. Another option is to make a mark on the gauge face at its present position--that mark represents normal cruise OP.
Your engine will have to be pretty tired for this OP to decrease much below your "normal" mark so when you see the needle below your mark (allowing for a little drop due to high temps or extended climbs) in cruise you should take note. Usually slightly low OP in a 4 cylinder Lycoming is caused by letting the oil quantity drop below 6 quarts.
The Lycoming engine in your Cessna is very happy when cruising at 85-90 PSI.
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High Oil Pressure 1 year 3 months ago #503

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When everything is off my Oil Pressure guage shows something above zero. When engine running it is over 100lbs. The spec says 90 is max and my mechanic put another guage on and found that at high RPM the pressure is only 85-90. Is there some sort of zero adjustment that could make the guage read zero when off and correct when on? After several checks the mechanic pronounced it reading 20lbs higher than normal 100% of the time, so a zero adjust could fix it. He did not know if one existed and I saw some taped over holes on the back of the guage; so I wondered...

Does anyone know?
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