Engine - Cylinder Wall Damage Assesment
Date: February 2004Order No.: S-B-01.30/15
Supersedes: 01/30 dated May 1994
Group: 01.30
SUBJECT:
SERVICE INFORMATION REGARDING THE ASSESSMENT OF CYLINDER WALLS OF ENGINES WITH ALUMINUM ALLOY CRANKCASE
This Service information contains the following guidelines which are intended to help determine the condition of the engine block and its suitability for further use. If this cannot be determined adequately using the borescope, the cylinder head(s) must be removed.
These guidelines are provided to assist the technician in properly assessing the condition and deciding on the continued use of the crankcase.
Normal Condition (Figure 1)
NOTE:
Engine cylinder wall displays matte gray surface, no hone marks.
Pressure Gloss Marks, smoothings (Figure 2)
NOTE:
Individual blank points, e.g. in the middle of cylinder or in the area of cylinder head bolts.
RE-USE CRANKCASE
Bright Circular Polished Upper Surfaces of Cylinder Wall (Figure 3)
NOTE:
Usually starting from the first piston ring, the upper area of the cylinder, with a measurable partial cylinder wear.
CRANKCASE IS UNUSABLE
Visible Stripes, Friction Marks (Figure 4)
NOTE:
Starting from the first piston ring, tapering to an end about 3Omm. Traces of dry rubbing which can be felt, caused by oil film being washed off by fuel, e.g. during frequent cold starts in short distance driving. These traces of rubbing which occur principally in the of the cylinder head bolts and on the pressure side are not a problem, provided they are smooth and piston rings are not damaged.
RE-USE CRANKCASE
Roughened Stripes, Friction Seizure (Figure 5)
NOTE:
Starting from the first ring, in the upper area of cylinder, with a measurable partial cylinder wear.
CRANKCASE IS UNUSABLE
Continuous Individual Traces of Scratch (Figure 6)
NOTE:
Caused by contaminants, e.g. through reverse pulsation of carbon particles from the exhaust.
RE-USE CRANKCASE
Ring Shaped Imprints (Figure 7)
NOTE:
Visible in the upper and lower reversal range of the piston rings.
RE-USE CRANKCASE
Piston Seizure (Figure 8)
NOTE:
Cylinder wall usually perceptibly roughed over the entire length. Material transfer and noticeable scoring that can be felt on the cylinder wall and piston skirt.
CRANKCASE IS UNUSABLE
Brown Coloring of Cylinder Surface (Figure 9)
NOTE:
Oil varnish is over large areas of the cylinder contact surface and indicates that the engine was driven at high temperature level.
RE-USE CRANKCASE provided only allowable cylinder distortion is not exceeded (refer to WIS document no. AR01.40-P-9201AA table BE01.40-P-1001-02E for specification). Oil varnish above piston ring area is normal.
NOTE:
When refering to WIS document: AR01.40-P-9201AA, please disregard the information contained in the table titled: Commercially available tools (see Workshop Equipment Manual). The equipment is listed for reference only and is not part of the MBUSA Standard Service Equipment Program.
Piston Rings are Lined-up in Cylinder Bore (No illustration shown)
NOTE:
If piston rings are lining up, check for cylinder bore roundness. Measure the diameter of the cleaned cylinder bore with an internal measuring instrument in the longitudinal and transverse directions, refer to WIS document no. AR01.40-P-9201AA
Crankcase is Unusable if measurement of diameter A" and diameter B" exceeded their permissible variation of cylinder bore shape. Reference table BE01.40-P-1001-02E contained in WIS document no. AR01.40-P-9201AA