Cylinder block (crankcase) (Mercedes-Benz S-Class W126)

During each major overhaul, all cavities and passages must be thoroughly cleaned and all remnants of old gaskets or sealant must be removed. This applies especially to oil passages. The cylinder block must be carefully checked for scratches and protrusions. Check the flatness of the cylinder block dividing plane. In addition to visual inspection, measurements of the cylinder bores are necessary, especially when searching for the causes of high oil consumption.

For this purpose, the cleaned cylinder bores are measured with an internal measuring device in three places - namely in the direction of the piston pin axis (direction a), and then perpendicular to it (direction to). With the pistons not removed, the third measurement point is slightly above the bottom dead center of the piston. If the cylinder bores are bored, the maximum allowance for honing should not exceed 0.05 mm.



For V8 engines, a device with a fixed measuring point must be used to measure the cylinder bores, otherwise the cylinder surfaces may be damaged. The cylinder surfaces of 8-cylinder engines are electrolytically treated after boring and honing. This "retracts" the aluminum so far that the piston rings and the chromed or iron-plated light metal pistons come into contact exclusively with silicide crystals, 0.02 to 0.05 mm in size, which provide a wear-resistant cylinder surface. These silicide crystals are formed after the electrolysis process. If this operation is not carried out, the result will be severe piston wear. Since this operation can only be carried out in specialized workshops, we will not describe its details here.

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