Valve Sticking; Oil Starvation/Sudden Loss Of Oil Pressure - Lycoming IO-390-D Series Maintenance Manual

IO-390-D Series Engine Maintenance Manual
IO-390-D Series Engine Maintenance Manual
H. Valve Sticking
The primary causes of intake or exhaust valve sticking are:
(1)
(a) Accumulated contaminants in the oil can collect on valve stems and/or guides to
prevent valve movement and cause intermittent engine hesitation or "miss." If the
contamination deposits are not removed, the valve becomes stuck and causes engine
damage.
(b) Conditions that can increase oil contamination and valve sticking include:
• High ambient temperature
• Slow flight with reduced cooling
• High lead content in fuel
• Oil changes and oil filter replacement not done as frequently as necessary. Refer to
the "Oil Servicing Schedule" in Chapter 12-10.
• Induction system not sealed - unfiltered air enters engine
• Cooling air baffles and/or baffle strip deterioration
• Sudden cool down of the engine that can occur with a rapid descent with reduced
power or engine shutdown without sufficient engine cooling.
NOTICE: If valve sticking is a problem, refer to the latest revisions of Service Letter No.
L197 and Service Instruction No. SI-1425 and complete the 1000-hour inspection
in Chapter 05-20. Refer to the section "Corrective Action for Valve Sticking" in
Chapter 72-30.
If the 1000-hour inspection is completed before 1000 hours of operation because
of valve sticking, complete the scheduled 1000-hour inspection after the next
1000 hours of engine operation from the time of this inspection unless valve
sticking occurs again.
I. Oil Starvation/Sudden Loss of Oil Pressure
(1) To operate correctly at various attitudes, the engine must be supplied with a sufficient
quantity of lubricating oil. Unless there is an adequate quantity of lubricating oil at all
times during flight, loss of oil pressure can occur.
NOTICE: Refer to Appendix A of the IO-390-D Series Engine Installation and
Operation Manual for the minimum oil quantity.
(2) Very often a sudden loss of oil pressure is quickly followed by a sudden rise in oil
temperature.
(3) As a preventive measure, before every take-off, complete the "Oil Level Check" in
Chapter 12-10. Make sure the oil level is above the minimum specified level in Appendix
A of the IO-390-D Series Engine Installation and Operation Manual.
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March 2020
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