Air Compressor Pin Bore Wear (012-010)
B3.9 and B5.9 Series Engines
Section 12 - Compressed Air System - Group 12
Bar the crankshaft over until the compressor piston reaches
top dead center (TDC), and the extension starts to move
downward approximately 3 to 6 mm [1/8 to 1/4 in].
NOTE: To prevent damage to the top of the piston, do not
use a hammer.
Give a quick, hard push downward on the extension and
listen for a metallic click as wear clearance is taken up.
If significant piston motion is felt or a metallic click is heard,
the pin bores can be worn, and the compressor must be
If no motion or sound is heard, the compressor is in sat-
isfactory condition and does not need to be replaced.
NOTE: Not all air compressors will exhibit pin bore wear.