Connecting Rod Inspection - Lycoming IO-390-D Series Maintenance Manual

10. Connecting Rod Inspection

Copy the Connecting Rod Inspection Checklist to record the condition of all of the connecting
rods and any corrective action.
Connecting Rod Inspection Checklist for IO-390-D Series Engines
Engine Model Number___________________ Engine Serial Number:___________________
Engine Time:_______________________ Date Inspection Done:_______________________
Inspection done by:______________________________
Disassemble the connecting rod; clean the rod and its cap thoroughly. Visually examine the
connecting rod for damage.
Task or Inspection
Examine the connecting rod bore for wear.
If the rod bore is worn, replace the
connecting rod assembly.
Examine the mating face of the connecting
rod and its cap face for fretting (Figure 34).
If fretting is found, replace the connecting
rod assembly.
Use a 6 power magnifying glass
(minimum) or bench microscope to
examine the critical areas on the connecting
rod identified in Figure 34 for galling.*
If galling is found, replace the connecting
rod assembly.
* Do not mistake stains or discoloration for galling. Surface blemishes are easily removed with a fine
abrasive cloth, chemical cleaner or steel wool. Whereas, galling cannot be removed. If galling is
found in the bearing bore, replace the connecting rod. If surface blemishes cannot be removed with a
fine abrasive cloth, chemical cleaner or steel wool, there is evidence of galling. Gall marks vary in
size and shape. Some gall marks can be as small as pin heads. Other gall marks can be circular, oval,
or thin, or look like rods.
Areas on Connecting Rod to Examine for Fretting and Galling
72-20
Page 152
IO-390-D Series Engine Maintenance Manual
IO-390-D Series Engine Maintenance Manual
Findings and/or Corrective Action
Cylinder 1 Cylinder 2
Acceptable Acceptable
Replace Replace
Acceptable Acceptable
Replace Replace
Acceptable Acceptable
Replace Replace
Figure 34
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Cylinder 3 Cylinder 4
Acceptable Acceptable
Replace Replace
Acceptable Acceptable
Replace Replace
Acceptable Acceptable
Replace Replace
March 2020