Cleaning
For a complete cleaning, the plugs should be removed, if required. Drill a small hole in the cork, then insert a self-tapping screw and pry the corks out with pliers. Remove all external parts (sensors, brackets, etc.).
Note that on some engines, a rubber plug located next to the bell housing flange on the cylinder block covers the hole for installing the TDC diagnostic sensor.
Scrape off all traces of the gasket from the cylinder block. being careful not to damage the mating surfaces.
Remove all grease port plugs where required. Their fit is usually very tight - they may have to be drilled out and the holes cut with a tap. Use new plugs when assembling the unit.
If the unit is heavily soiled, it should be cleaned with a steam jet.
After cleaning the block with steam, it is necessary to clean all the lubrication channels and oil filling holes. Rinse all internal channels with warm water. Dry the block thoroughly and coat all machined surfaces with a thin layer of oil. If there is a source of compressed air nearby, blow out all lubrication passages and oil fill holes (wear protective goggles when working with compressed air).
If the block is relatively clean, cleaning can be done with soapy water and a stiff brush. After thoroughly cleaning the lubrication holes and oil filling holes, coat the machined surfaces with a thin film of oil.
After coating the mating surfaces of the new plugs with an appropriate sealant, install them on the cylinder block. Make sure they are straight and correctly installed, otherwise there may be a leak.
If the engine must be left disassembled for some time, install the main bearing caps, tighten the bolts by hand and cover the cylinder block with a large plastic bag to protect the engine from dirt and corrosion.
Inspection
Visually inspect the block for cracks, rust, and corrosion. Check for thread damage. If defects are found, try to repair the unit, otherwise the only solution may be to replace it.
Check the cylinder bores in the block for taper, ovality, burrs and scratches. Begin by carefully inspecting the top of the cylinder mirror where there may be "scallops".
Measure the diameter of each cylinder at the top (just under the comb), in the central and bottom parts of the cylinder parallel to the axis of the crankshaft.
Then measure the diameter of the cylinders at the same three points, but at right angles to the axis of the crankshaft. Compare the obtained results with the required ones. Repeat the operations for the rest of the cylinders. If the wear of the cylinder exceeds the allowable limits, or if there are strong scuffs and scratches on its walls, it is necessary to bore it and pick up new pistons.
- a) In factories, piston and cylinder diameters are closely matched. The actual piston diameter is indicated on the piston head; the same numbers on the engine crankcase indicate the cylinder diameter.
- b) After boring the cylinders, it is necessary to carefully measure and select the pistons to ensure the necessary clearance between the walls of the cylinder and the piston.
- c) The piston diameter is measured from the bottom of the skirt.
If wear is at the limit and within tolerance, new special piston rings can be supplied to compensate for wear.
In this case, the holes are honed to ensure that the new rings fit correctly and provide an effective seal.
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