MTU Detroit Diesel 183 Series Technical Publication page 185

Task Description
20080/1 E 98-12
Replace complete piston if signs of contact erosion are
present at the piston edge.
Remove scoring or scuffing on the top land if local and
not extending as far as the first annular groove.
Replace piston if damage is more extensive, i.e. if
scoring or pitting extends as far as the first annular
groove (arrow).
In the event of extensive polishing wear on piston skirt
(appears dull rather than shiny) and concentrated
scoring, replace piston.
Replace pistons exhibiting even minor, localized
scuffing on piston skirt.
Measure piston skirt diameter
Use an outside micrometer to measure diameter on
points free of graphite.
If measurements are below limit values as per
Tolerances and Wear Limits List, replace piston.
Inspecting piston ring grooves
Check groove width with final measurements.
Alternatively, a new piston ring (2) can be fitted and
axial clearance checked with feeler gauge (1).
If the limit values as per Tolerance and Wear Limits List
are exceeded, or the measurements are below limits for
the oil control-ring groove, replace piston.
Group 03
Subgroup 7004
Page 5