IO-390-D Series Engine Maintenance Manual
© 2020 Avco Corporation. All Rights Reserved
05-30
March 2020
Page 41
IO-390-D Series Engine Maintenance Manual
F.
Grit-Blasting the Combustion Chamber in an Engine Cylinder:
(1)
Remove the intake and exhaust valves from the cylinder to be cleaned. Refer to Chapter
72-30.
(2)
Remove the spark plugs from the cylinder. Refer to the section “Spark Plug Removal” in
Chapter 74-20.
(3)
Complete the "Grit-Blast Procedure” in this chapter.
(4)
Record the cleaning for future reference to identify trends and engine operating time for
lead build up to occur.
(5)
Wipe the cylinder with a clean, white cloth dipped in SAE 10 engine oil. Examine the
cloth under a light for evidence of any abrasive residue remaining in the cylinder. If any
residual abrasive is found, repeat the earlier steps in this procedure until there is no
abrasive residue.
11.
Piston Cleaning
CAUTION
DO NOT USE A STEEL BUFFING BRUSH TO CLEAN THE RING LANDS
AND SKIRT OF A PISTON. DO NOT GRIT-BLAST PISTON RING
GROOVES OR PISTON SKIRTS. THESE METHODS CAN STRETCH THE
SIDES OF THE PISTON RING GROOVES AND ROUND OFF THE OUTER
CORNER OF THE PISTON RING LANDS, WHICH AFFECTS THE PISTON
CONFIGURATION.
A.
Remove all oil or preservative oil accumulation from the piston by a soak or wash in a clean
bath of mineral spirits, Safety Solvent, or equivalent degreasing solvent in compliance with
MIL-PRF-680 specifications.
B.
Remove any remaining deposits with a wooden scraper.
C.
Gently clean the piston pin bore with a soft bristle non-
metallic brush (Figure 2). Use a gentle twist motion to
clean each bore.
D.
After cleaning one side, turn the piston 180° and repeat
the previous step to ensure the entire bore is free of
FOD.
E.
Soak the piston again in a new clean bath of mineral
spirits, Safety Solvent, or equivalent degreasing solvent
in compliance with MIL-PRF-680 specifications to
remove remaining deposits.
F.
Clean the piston ring grooves thoroughly so there is no
debris in the grooves.
Figure 2
Cleaning the Piston Pin Bore with
a Soft Bristle Non-Metallic Brush
12.
Injection Nozzle Cleaning
A.
Remove the injection nozzle per the “Injection Nozzle Removal” procedure in Chapter 73-10.
CAUTION
NEVER USE A SHARP TOOL SUCH AS A WIRE OR PIN TO CLEAN
AN INJECTION NOZZLE. DAMAGE TO THE INLET AND OUTLET
FUEL RESTRICTORS COULD OCCUR WHICH WOULD CHANGE THE
FUEL FLOW.
