MTU 12 V 2000 M40A Operating Instructions Manual page 158

Findings
Burn mark
Seizure marks, scuff‐
ing
Evaluation of findings and further measures
The findings in the start phase of oxidation discoloration and heat discoloration are similar. A thorough
investigation and compliance with the above evaluation criteria allow an unambiguous evaluation. To
avoid unnecessary disassembly work, it is recommended that another inspection be carried out after fur‐
ther operation of the engine.
158 | Task Description | MS150031/05E 2013-01
Action
This is caused by a malfunction in the liner / ring tribosystem. Usually they run
over the whole ring-travel area (TDC/BDC), starting at the first TDC-ring and be‐
coming more visible from the second TDC-ring 2 onwards and less pronounced
from TDC-ring 1. The honing pattern is usually no longer visible and displays a
clearly defined (straight) edge to the undisturbed surface. The damaged surface
is usually discolored. The circumferential length varies.
Liners with burn marks, or heat discoloration, starting in TDC-ring 1 have to be
replaced.
Irregular circumference lengths and depths. Can be caused either by the piston
skirt or the piston crown. Material deposits on the liner (smear), heavy discolora‐
tion. Severe, visible scoring.
Replace liner.