Inspecting cylinders with light probe, assessing cylinders - RA01001190200X(01-0200)

WARNING: This page does not describe the selected car, but rather 42 other vehicles, including the 1999 Mercedes-Benz S600, 1999 Mercedes-Benz S500, 1999 Mercedes-Benz S420, 1999 Mercedes-Benz S320, and 1999 Mercedes-Benz CL600. However, it is still accessible from the selected car via links, so may be relevant.

Preceding work:

Removing, installing spark plugs (REPLACE SPARK PLUGS )

Hazard warnings when hood opened (01-0085)

Operation no. of operation texts and work units or standard texts and flat rates

Fig 1: Inspecting Cylinders With Light Probe

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

COMMERCIALLY AVAILABLE TOOL

Cylinder inspection lamp

e.g.

Karl Storz GmbH,
78532 Tuttlingen
Motoskop TW (cold light)
with lens probe
103 26 CT (210 mm)

Piston	position to BDC, see table.
Motoskop and lens probe	connect. Motoskop TW 12 V to car battery Motoskop TW 220 V to mains.
Lens probe	insert into cylinder, remove.
Cylinder	inspect, assess, see note.

Marking index on TDC pointer	Piston in BDC position
0	4 and 7
90	8 and 2
180	1 and 6
270	5 and 3

NOTE: If complaints are received regarding an engine because of noises, overheating, oil consumption etc., it is good practice to perform a visual inspection with a cylinder inspection lamp with the cylinder head installed.

The information which follows is designed to help in assessing the cylinder walls, in taking a proper professional decision regarding the condition and further use of the crankcase.

Normal condition
Mat grey surface, no honing pattern.

If it is not possible to assess the cylinders with sufficient certainty by means of a visual inspection with the cylinder inspection lamp, the cylinder head should then be removed.
Bright pressure marks, smoothing
Individual bright points e.g. in the middle of the cylinder or in the area of the cylinder head bolt pipes.

Continue using crankcase.

Fig 2: Identifying Bright Points In Middle Of Cylinder
Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
Bright cylinder surfaces, polished and reflective all round
Usually starting from the first piston ring, in the top area of cylinder, with measurable partial cylinder wear.

Cylinder wall unserviceable.

Fig 3: Identifying Bright Cylinder Surfaces
Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
Visual streaks, traces of rubbing
Starting from first piston ring, extending for about 30 mm. Traces of dry rubbing which cannot be felt, caused by fuel ablution of the oil film, e.g. frequent cold starting in short-distance driving. These traces of rubbing, which are likely to be found in the area of the cylinder head bolts and on the pressure side, are acceptable if smoothed. The piston rings are not damaged. Continue using crankcase.

Fig 4: Identifying Visual Streaks, Traces Of Rubbing
Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
Roughened streaks, traces of seizure
Starting from the first and second piston ring and extending initially to the bottom part of the cylinder.

Traces of rubbing as described in section 4 have progressed to seizure. Piston rings may be damaged.

If the streaks can be felt, cylinder wall unserviceable.

Fig 5: Identifying Roughened Streaks, Traces Of Seizure
Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
Ring-shaped impressions
Visible in the top and bottom piston ring reversal area, are acceptable.

Continue using crankcase.

Fig 6: Identifying Ring-Shaped Impressions
Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
Traces of individual, continuous scratches
Caused by dirt, e.g. by soot particles being pulsated back out of the exhaust.

Continue using crankcase.
Piston seizure
Cylinder wall usually roughened over the entire length to the extent that this can be felt.

Material accumulation and traces of seizure on cylinder wall and piston skirt which can be felt.

Cylinder wall unserviceable.
Brown discoloration of cylinder surfaces
Oil varnish exists over considerable areas of the cylinder wall and indicates that the engine has been driven in a very high temperature level.

Continue using crankcase provided no impermissible cylinder distortion exists.

Oil varnish above the piston ring zone is normal and is acceptable.