Yanmar Excavator Hydraulic Pump: Your Ultimate Guide to Maintenance and Replacement

The way to prevent hydraulic pump failure includes regular maintenance, keeping the hydraulic oil clean, regularly changing filters, and avoiding overload operation.

Park the excavator on a flat ground, turn off the engine and wait for a while, then check the hydraulic oil level through the oil level gauge of the hydraulic oil tank.

1. 1. Insufficient air intake: Check whether the intake valve clearance is within a reasonable range. Unequal valve clearance will cause insufficient intake pressure and volume; whether the air filter is clogged. The supercharger is damaged, resulting in insufficient intake pressure;

2. The diesel quality is poor, and the diesel pump and fuel injector are worn;

3. Injector wear: Excessive fuel injection leads to incomplete combustion. Service personnel are required to perform an engine cylinder disconnection experiment to check whether it is caused by wear of the fuel injector.

First, check the oil level and add oil if it's low. Inspect the oil filter for clogs or restrictions, and replace it if necessary. Check the oil pump for wear or damage, and test the oil pressure sensor for accuracy. If these components are functioning correctly, inspect the engine bearings and journals for excessive wear.

Reasons from the piston group
1. The piston ring gap 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 heat expansion when the engine is working, and it will be pressed tightly against the cylinder wall, or the piston ring will be broken, which can easily pull out grooves on the cylinder wall.
2. The piston pin is out. Because the piston pin retaining ring is not installed or falls off or breaks, the piston pin will be out during movement, which can easily damage the inner wall of the cylinder and cause the cylinder to blow into the crankcase.
3. The piston cylinder gap is too small or too large. If the piston material is poor, the manufacturing size error is too large, or the piston is deformed after the piston pin is assembled, the matching gap between the piston and the cylinder is too small, and the piston is stuck after heat expansion, which will then damage the cylinder wall.
4. The piston ring is seriously carbonized. Excessive carbon deposits cause the piston ring to stick or bite in the ring groove. At the same time, carbon deposits are a hard abrasive that will grind into longitudinal grooves on the cylinder wall.
5. The piston is seriously off-cylinder. Due to the bending and twisting of the connecting rod, the parallelism and coaxiality deviations of the connecting rod journal, main journal, and piston pin seat are too large, causing the piston to be significantly off-cylinder, which will accelerate the wear of the piston ring, piston and cylinder wall and destroy the formation of the oil film.

Reasons for cylinder sleeves
1. The roundness and cylindricality tolerances of the cylinder sleeves exceed the allowable range, which greatly reduces the sealing of the piston and cylinder sleeves. The high-temperature gas in the cylinder flows down, destroying the oil film between the piston and the cylinder wall, and then causing cylinder pulling.
2. The cylinder sleeve is deformed during the assembly process. For example: the protrusion of the upper end surface of the cylinder sleeve is too large, and the cylinder sleeve is deformed after the cylinder head is installed; the cylinder sleeve water blocking ring is too thick, and the cylinder sleeve is deformed after being pressed into the body, which can easily cause cylinder pulling.

Reasons for use:
1. Whether the size of the cylinder sleeve used during assembly does not match the cylinder body and piston.
2. The air filter is not sealed, which makes the filtering effect worse. Dust, sand and other impurities in the air are sucked into the cylinder, forming abrasive wear. Tests show that if a few grams of dust are sucked in every day, the wear of the cylinder liner will increase by more than 10 times.