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IO-390-D Series Engine Maintenance Manual
IO-390-D Series Engine Maintenance Manual
Problem
Engine surges (Cont.) Low engine oil level
Irregular oil pressure
Low oil pressure
© 2020 Avco Corporation. All Rights Reserved
March 2020
Table 1 (Cont.)
Fault Isolation Guide
Cause
Malfunctioning
propeller governor
Breather is blocked
Faulty oil pump
Propeller blades are
intermittently sticking in
hub
Front main bearing has
too much clearance
Oil pump is sucking air
Oil not of the correct
viscosity for ambient
temperature
Low engine oil level
High oil temperature
Corrective Action
Complete a check of the oil level. Add
oil. Refer to the sections "Oil Level
Check" and "Add Oil to the Engine."
Replace the propeller governor.
Examine the breather for obstructions.
Remove all obstructions.
Replace the oil pump.
Remove and overhaul the propeller as
per the propeller manufacturer's
instructions.
Complete a "Propeller Oil Control
Leak Test."
Replace the oil pump per the "Oil
Pump Removal" and "Oil Pump
Installation" procedures..
Make sure oil of the correct viscosity
for the ambient temperature is used.
Refer to the latest revision of Service
Instruction No. SI-1014.
Complete the "Oil Level Check"
procedure.
Examine the engine for these
conditions:
1. Low oil level
2. Incorrect grade/weight of oil Refer
to the latest revision of Service
Instruction No. SI-1014.
3. Oil cooler bypass valve seating and
operation
4. Partial or full blockage in oil cooler
lines
5. High cylinder head temperature
6. Excess blow-by
7. Blockage in air duct to the oil
cooler
8. Non-conforming temperature gage.
Ref.
12-10
AMM
72-25
72-20
72-25
12-10
12-10
72-50
AMM
12-30
Page 91
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