Detroit Diesel 4000 Series, Service Manual, Page: 535 / 2706

SERIES 4000 12/16V SERVICE MANUAL
[b] If not worn, pitted or scored, continue inspection.
2. The piston skirt wear pattern must cover most of the surface. The friction scores (3) in this
area must be easily identifiable. See Figure 284.
1. Piston Crown 4. Piston Crown Bolt
2. Piston Skirt 5. Pressure Plate
3. Friction Scores
Figure 284 Checking Piston Skirt Wear Pattern
NOTE:
The friction scores on the circumference are artificial depressions which are filled with oil
and result in improved lubrication.
3. Inspect the piston edge for heavy contact, wear, pitting, scoring or erosion.
[a] If piston edge shows signs of heavy contact, wear, pitting, scoring or erosion,
replace the piston.
[b] If piston edge is not worn, pitted, scored or eroded, continue inspection.
4. Inspect piston for scoring or scuffing on top land (piston crown).
[a] Remove scoring or scuffing on top land (piston crown) of piston if localized and does
not extend as far as first ring groove.
All information subject to change without notice.
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