Inspection and restoration of cylinders in the block (Mercedes-Benz E-Class W123)

1. Check the cylinder bores in the block for taper, ovality, scoring, and scratches. Start by carefully inspecting the top of the bores. If they are worn, a small ridge will form on their thrust side, which marks the top of the piston ring travel. The car owner will easily recognize the wear of the cylinder surface even before disassembling the engine. Excessive oil consumption and blue smoke from the exhaust system are sure signs of cylinder and piston ring wear.

2. Measure the cylinder diameter under the "wear ring" with a micrometer and compare it with the diameter at the bottom of the cylinder bore, where the cylinder does not wear. If the difference between the two measurements exceeds 0.15 mm, the cylinders must be bored and pistons of a repair size must be installed.

3. Cylinder bores must be machined to provide optimum working clearance with new oversize pistons. The difference in weight between any two of the six pistons must not exceed the limits specified in the specifications.

4. If the cylinder bores are slightly worn, but not so much that they need to be reamed, special oil scraper rings and pistons can be installed, which will restore the necessary compression and stop the burning of oil in the engine. Several different sizes of repair parts are available for this purpose, and the manufacturer's instructions for their installation should be strictly followed.

5. Check the cylinder block and crankcase for cracks and other damage, and make sure all water and oil passages are clear. Check that all cover gaskets are securely fastened to the crankcase and cylinder block. If any gaskets are in doubt or leaking, loosen the cover mounting screws and remove the cover. Clean the cover and seating surface, install a new gasket, insert and tighten the screws. Check for leaks through the cooling jacket plugs.