Piston Inspection - Lycoming IO-390-D Series Maintenance Manual

IO-390-D Series Engine Maintenance Manual
IO-390-D Series Engine Maintenance Manual

10. Piston Inspection

A. Copy and complete the Piston Inspection Checklist.
(1) Examine the entire piston for damage or discoloration from burns.
(2) Examine the piston grooves for wear. Measure the piston ring clearance and compare to
measurements in the latest revision of the Service Table of Limits - SSP-1776.
Engine Model Number:__________________Engine Serial Number:________________________
Engine Hours: ___________________________Inspection Date:____________________________
Inspection Item
Before cleaning the piston, examine the following
areas on the piston for pitting, cavities and surface
distortion (which can be an indication of detonation
or pre-ignition):
• Top of the piston
• Piston ring lands and grooves
• Piston pin holes
• Piston pin whole bosses
• Look for deposits or damage
Complete the "Piston Cleaning" procedure in
Chapter 05-30.
NOTICE: Surface distortion can be an indication
of detonation or pre-ignition.
After Cleaning:
• Look for cracks on the piston head or skirt.
Replace the piston if a crack is found.
• Look for bent or broken lands. Replace the
piston if the land is broken or bent.
• Look for scoring on the piston skirt, damage or
discoloration from burns. Replace the piston if
scoring, damage or discoloration found. Identify
and correct the cause.
• Examine the piston grooves for wear. Replace
the piston if high ridges are on the lower lands.*
* High ridges of displaced metal can interfere with operation of new piston rings. The displaced metal
can cause excessive piston ring clearance.
© 2020 Avco Corporation. All Rights Reserved
March 2020
Piston Inspection Checklist
Cylinder 1
Cylinder 2
Cylinder 3
Cylinder 4
Cylinder 1
Cylinder 2
Cylinder 3
Cylinder 4
Findings/Corrective Action
72-30
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