4D95S-W-1 Diesel Engine Piston 6202-32-2140 6201-32-2121 104mm high For KOMATSU

judge

During vehicle operation, some parts of the engine experience abnormal piston knocking noise. The abnormal sound of piston knocking on the cylinder occurs in the upper part of the cylinder, which is a rhythmic "tap" sound similar to using a small hammer to hit the cement floor. When the engine is idling, the sound is obvious and clear. Especially when the engine is running at low temperatures, the sound becomes noticeable, and as the temperature increases, the sound decreases or even disappears.

Judgment method for piston knocking:

(1) Cut off oil cylinder by cylinder. The method of cutting off oil cylinder by cylinder is adopted to determine the position of knocking the cylinder. If the oil is cut off to a certain cylinder, the sound significantly decreases or disappears, and when the oil supply is restored, a clear "click" sound can be heard, indicating that the piston of the cylinder is knocking the cylinder.

(2) To further confirm that the piston of the cylinder is knocking, the fuel injector of the cylinder can be removed, a small amount of CD grade turbocharged oil can be added to the cylinder (for sealing purposes), and then the fuel injector can be installed to start the engine. The knocking sound disappears or weakens, and after running for a while, the knocking sound reappears, indicating that the piston of the cylinder is knocking.

The main reasons for piston knocking are as follows:

(1) The gap between the piston and the cylinder wall is too large. The standard clearance between the piston skirt and cylinder of WD615 series engines is 0.143-0.182, and the maximum wear limit is 0.35-0.40.

(2) After the engine has been running for a period of time, the cylinder piston experiences wear, coupled with poor lubrication. The fit gap between the piston and the cylinder increases due to wear, and a severe step appears slightly below the first air ring, causing the piston to strike the cylinder and make a strange noise.

Piston inspection mainly includes measurement of skirt diameter, piston ring groove height and piston pin seat hole size:

① The selection of pistons should be determined according to the repair size of the cylinder. Usually, the size value is increased and marked on the piston crown;

② In the same series of fish feeding clusters, the piston structure may not necessarily be the same. Therefore, when selecting pistons, the corresponding type of piston must be selected based on the type of engine. On the same engine, pistons of the same brand, group, or product code should be selected; The same model must use pistons with the same product code to ensure that the difference in piston diameter and quality does not exceed the range specified by the original factory. Otherwise, it may cause engine combustion problems, rough operation, reduced economy and power performance, etc. Therefore, when selecting pistons, the corresponding model of piston must be selected based on the type of engine.