Inspection

Remove the piston rings from the piston. To do this, use the appropriate tool or old probe, since the ring is very brittle and break. Always remove the upper piston rings. Their reuse is not allowed.

Remove the carbon deposits in the piston grooves. For this you can use a piece of old piston ring.

Carefully remove all traces of soot from the bottom of the piston. After removing sediment clean pistons and rods with kerosene or with a suitable solvent and completely dry. Clean oil passage in the annular grooves.

Inspect the piston for signs of wear or damage. Permissible to consider the wear in a vertical "grain" in the pressure receiving surface of the piston or a small gap of landing the top compression ring in the groove. Scoring or scratches on the piston skirt may indicate that the engine was overheated due to poor cooling, lubrication or too high combustion temperatures. Traces of erosion on the skirt are a sign of leakage of gas from the combustion chamber, possibly caused by the wear of the cylinder wall or the piston rings. Traces of burning or chipping on the underside of the piston is usually a sign of detonation combustion caused by ignition or early use of low-quality gasoline. For this reason, in some cases it may be melt piston head. Traces of galvanic corrosion on the piston crown indicate that leakage of coolant occurs in the combustion chamber, and (or) the sump.

All of the fault that caused these lesions should be removed before the engine is returned to operation, since otherwise a deterioration occurs again.

A micrometer to measure the diameter of all four pistons at a point 10 mm from the bottom of the skirt at right angles to the piston pin axis. Compare the results of the measurement with the values listed in Table. 2.8. If the diameter of the piston is out of tolerance, replace the piston kit. Keep in mind that the cylinder block can be squandered while previous overhaul, respectively, could be mounted pistons oversized. Record measurement results and use them to check the gaps later, when they measured the diameters of the cylinder bores of the engine.

Insert the new piston ring side in the corresponding groove and measure the gap between the ring and the wall of the groove with a feeler gauge (Fig. 2.21). Note that the rings have different thicknesses, and therefore the groove and the ring must match. Compare the results of measurements with the required values, and if the clearances are outside the tolerance, replace the piston.

Carefully inspect the connecting rods, piston pins and connecting rod cap for cracks. Measure the diameter of the hole caliper in the top head of a rod and the diameter of the piston pin. Subtracting the diameter of the piston pin diameter from the top head of a rod, determine gap. If he is out of tolerance, the need to expand the hole in the piston and connecting rod sleeve top and install a new piston pin.