Piston Rings and Grooves
Inspection / Checking
A5.05. 02.07.01.03
30000, 7500
M20
en / 31.05.2010 IB022421 2/3
02
1.4 Remove the piston rings only with the
correct tool (Fig. 1/W1). Maintain previous
position of the rings referring to the
mounting position of the piston given in the
measuring sheet.
1.5 Clean piston rings.
1.6 Check the the chrome layer for wear,
especially at the cut and at the opposite
side. Renew all rings of this piston even if
only parts of the chrome layer is no longer
visible.
If the chrome layer of one piston ring has
been worn, check the rings of all pistons.
1.7 Clean the piston, ring grooves and oil return holes for the scraper scraper ring.
1.8 Smooth slight friction and seizing marks with an oily fine emery cloth or fine carborundum stone.
Renew the piston in case of heavy damage or deep scores.
1.9 Measure the groove width h
N
(Fig. 2) in the front area of the groove in longitudinal and transverse
directions of the engine. When exceeding the limits, have the ring grooves reconditioned by MaK.
1.10 Measure the ring thickness h
R
(Fig. 2) at 4 different points.
h
N1
= new
h
N2
= worn
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