Why does the piston always pull the cylinder liner?
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Why does the piston always pull the cylinder liner?

One: Piston components

1.The piston ring clearance is too small. If the opening gap, side gap or back gap of the piston ring is too small.

The piston ring will be stuck due to thermal expansion when the engine is working.

If it is pressed tightly against the cylinder wall, or the piston ring is broken, it is easy to pull out the groove on the cylinder wall.

2.Piston pin blew out. Because the piston pin circlip is not installed or falls off or breaks, the piston pin bounces out during the movement.

It is easy to strain the inner wall of the cylinder, causing the cylinder to blow-by to the crankcase.

3.The clearance between the piston and the cylinder is too small or too large. If the material of the piston is poor.

The manufacturing size error is too large, or the piston is deformed after the piston pin is assembled,

As a result, the matching clearance between the piston and the cylinder is too small, and the piston is stuck after being heated and expanded, which in turn strains the cylinder wall.

4.Severe carbon deposits on the piston ring. Excessive carbon deposits cause the piston ring to stick or seize in the ring groove.

At the same time, the carbon deposits are a hard abrasive, which will grind into longitudinal grooves on the cylinder wall.

5.The piston is severely eccentric to the cylinder. Due to the bending and twisting of the connecting rod.

The deviation of the parallelism and coaxiality of the connecting rod journal, main journal, and piston pin seat is too large,

Causing the piston to deviate significantly from the cylinder, which will accelerate the wear of the piston ring, piston and cylinder wall, and destroy the formation of the oil film.

Second: the cylinder liner

1.The roundness and cylindricity tolerances of the cylinder liner exceed the allowable range, which greatly reduces the sealing performance of the piston and the cylinder liner.

The high-temperature gas in the cylinder moves downwards, destroys the oil film between the piston and the cylinder wall, and causes the cylinder to pull.

2.The cylinder liner is deformed during the assembly process. For example, if the upper end surface of the cylinder liner protrudes too much, the cylinder liner will be deformed after installing the cylinder head.

The water blocking ring of the cylinder liner is too thick, and the cylinder liner will be deformed after being pressed into the body, which will easily cause the cylinder to pull.

Third: Improper use and other aspects

1.The air filter is not sealed, which makes the filtering effect worse. The dust, sand and other impurities in the air are sucked into the cylinder to form abrasive wear.

Tests have shown that if a few grams of dust is sucked in every day, the wear of the cylinder liner will increase by more than 10 times.

2.Poor running-in. For new or overhauled engines, there are many microscopic unevennesses on the surface of cylinder liners, pistons, piston rings and other parts, making it difficult to form a lubricating oil film.

If it is put into high-load operation immediately without running-in, it is easy to cause accidents such as cylinder pulling.

3.Start at low temperature often. When the engine is started at low temperature, the lubricating oil has high viscosity and poor fluidity, and it is difficult to form an effective oil film on the inner wall of the cylinder.

According to tests conducted by the research department, the wear of cylinder liners and other parts of the diesel engine when the cooling water temperature is below 30°C is 5 to 7 times that of normal water temperature.

4.The engine is overheated. When the cooling system is poorly maintained or overloaded, the excessively high machine temperature not only reduces the mechanical strength of the parts, but also prevents the formation of a lubricating oil film on the inner wall of the cylinder.

After the pistons and other parts are heated and expanded, they are easy to get stuck in the cylinder liner.

The consequence is often that the piston is partially melted and the inner wall of the cylinder liner is damaged, forcing the engine to stall.

5.Long-term use of engine oil. Engine oil needs to be replaced regularly. If it is not replaced for a long time, it will cause poor lubrication of the engine.

Iron filings in the oil will circulate to the piston again, which will not only fail to provide lubrication.

But will increase the friction coefficient between the piston and the cylinder liner and run for a long time. Cause the cylinder to be strained.

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