MTU 12 V 2000 M72 Operating Instructions Manual page 77

Finding
Discolorations (Heat)
Seizures, Seizure
marks
Evaluation of findings and further measures
The findings in the start phase of oxidation discoloration and heat discoloration are similar. Thorough in‐
vestigation and compliance with the above evaluation criteria allows a definite evaluation. To avoid un‐
necessary disassembly work, it is recommended that another inspection be carried out after further oper‐
ation of the engine.
Action
These are caused by a disturbance in the liner / ring tribosystem. Usually they
run over the whole ring-travel area (TDC/BDC), starting at the first TDC-ring
and becoming more visible from the second TDC-ring onwards and less pro‐
nounced from TDC-ring 1. The honing pattern is usually no longer visible and
displays a clearly defined (straight) edge to the undisturbed surface. The dam‐
aged surface is usually discolored. The circumferential length varies.
Liners with heat discoloration starting in the TDC-ring 1 have to be replaced.
Irregular circumference lengths and depths. Can be caused either by the pis‐
ton skirt or the piston crown. Material deposits on the liner (smear), heavy dis‐
coloration. Severe, visible scoring.
Replace liner.
M015650/03E 2011-10 | Task Description | 77