DETROIT DIESEL 53
Piston and Piston Rings 1.6
THIS PISTON SUITABLE FOR
SLIGHTLY SCORED, USE ONLY
BADLY SCORED-UNFIT
INSTALLATION AS IS
AFTER REMOVING SCORE MARKS
FOR USE
BY POLISHING WlTH CROCUS
CLOTH OR HARD INDIA STONE
4094
Fig. 4 Comparison of Pistons
introduced into the cylinders and will reduce the rate
Other factors that may contribute to piston failure
include oil leakge into the air box, oil pull-over from
of wear.
the air cleaner, dribbling injectors, combustion blow-
by and low oil pressure (dilution of the lubricating
Long periods of operation at idle speed and the use of
oil).
improper lubricating oil or fuel must be avoided,
otherwise a heavy formation of carbon may result and
Inspect and measure the piston pin bushings. The
cause the rings to stick.
piston pin-to-bushing clearance with new parts is
.0025" to .0034" A maximum clearance of .010" is
Keep the lubricating oil and engine coolant at the
allowable with worn parts. The piston pin bushings in
proper levels to prevent overheating of the engine.
the connecting rod are covered in Section 1.6.1.
Examine the piston for score marks, cracks, damaged
ring groove lands or indications of overheating. A
Remove Bushings from Piston
piston with light score marks which may be cleaned up
may be re-used (Fig. 4). Any piston that has been
1. Place the piston in the holding fixture J 1513-1 so
severely scored or overheated must be replaced.
that the bushing bores are in alignment with the hole
Indications of overheating or burned spots on the
in the fixture base.
piston may be the result of an obstruction in the
connecting rod oil passage.
Replace the piston if cracks are found across the
internal struts. Use the magnetic particle inspection
methods outlined in Section 1.3 under Crankshaft
2. Drive each bushing from the piston with the
Inspection for locating cracks in the piston.
bushing remover J 4972-4 and handle J 1513-2
(Fig. 5).
Check the cylinder liner and block bore for excessive
out-of-round, taper or high spots which could cause
failure of the piston (refer to Section 1.0 for
specifications).
Install Bushings in Piston
1. Place the spacer J 7587-1 in the counterbore in the
Inspection of the connecting rod and piston pin are
fixture J 1513-1 (small end up).
covered in Section 1.6.1.
SEC. 1.6 Page 3
April, 1974
