Views: 0 Author: Site Editor Publish Time: 2026-05-23 Origin: Site
Hydraulic system malfunctions in excavators can indeed be a real headache. Typically, we can categorize these issues based on their symptoms into several main types: “complete loss of movement,” “sluggish and weak overall movement,” “partial movement failure,” and “excessively high oil temperature.” We can then proceed with a systematic troubleshooting process.
Symptoms | Priority Checks | Troubleshooting Steps |
No movement throughout the vehicle (Engine running normally; all controls are unresponsive) | 1. Hydraulic fluid level and filter 2. Pilot circuit pressure 3. Power connection - Insufficient hydraulic fluid or a clogged suction filter, preventing the pump from drawing fluid. | - A faulty pilot pump, a blocked pilot line, or a leak in the pilot line results in insufficient pilot pressure (normally approximately 3.5 MPa), preventing control of the main valve. - A damaged coupling prevents engine power from being transmitted to the main pump. |
Overall operation is slow and lacks power (All movements feel sluggish; unable to dig through soil) | 1. Main pump performance (difference between “cold” and “hot” conditions) 2. Main relief valve pressure 3. Hydraulic fluid quality - Internal leakage in the main pump: A typical symptom is strong power when the engine is cold and weak power when it is hot-38. | -This can be determined by comparing speeds under cold and hot conditions or by checking the return filter for metal particles. - Main relief valve set pressure is too low or the valve is sticking, resulting in insufficient system operating pressure. - Hydraulic fluid has deteriorated or is of the wrong grade; viscosity that is too high or too low will affect power transmission. |
Partial Motion Malfunctions (e.g., unilateral travel deviation, failure of a specific function) | 1. Check the corresponding hydraulic circuit pressure 2. Check the control valve and actuators - Uneven pressure: For example, travel deviation is typically caused by different pressures in the left and right motors; this can be verified by measuring with a gauge. | - Stuck spool or pilot circuit issues: For example, if rotation does not occur, try swapping the suspected spool or oil line to quickly identify the fault location. - Internal leakage in the motor or cylinder: This can be detected by measuring pressure, observing movement, and inspecting for leaking oil lines. |
Excessive oil temperature (exceeding 70–80°C) | 1. Cooling system 2. System pressure setting 3. Condition of hydraulic oil | - A clogged radiator or a loose fan belt results in insufficient cooling airflow. - A faulty return check valve causes hot oil to flow directly back to the tank without passing through the radiator. - System pressure is set too high or the system is in overflow mode for extended periods, generating excess heat. - Insufficient oil in the tank reduces the total volume of circulating fluid, leading to rapid temperature rise. |
Swap-and-Test Diagnosis: Begin with a preliminary assessment by looking (oil leaks, damage), listening (unusual noises), and feeling (vibration, temperature). For small components such as valves, use the “swap-and-test method”—replace the faulty part with a known-good one to quickly pinpoint the issue.
Make Effective Use of Gauges: When visual inspection is inconclusive, measuring pressure at key points in the system with a pressure gauge is the most direct and effective method.
Create a Fault Tree (Principle-Based Reasoning): When a fault is complex, refer to the hydraulic system schematic, break down the circuit by function, and troubleshoot step by step.
Hydraulic pumps (especially the main pump) are the core of the hydraulic system and are expensive. Pay attention to the following signs, which may help you avoid costly repairs:
Slower Operation: As mentioned above, strong performance when cold and slower operation when hot is a typical sign of increased internal leakage in the hydraulic pump.
Unusual noises: The normal “humming” sound becomes irregular, or even turns into a “tick-tick-tick” or “clack-clack-clack” metallic clanging, indicating severe internal wear.
“Silver powder” in the fluid: Check the return oil filter or wipe the dipstick with a paper towel. If you find shiny metallic powder, it indicates severe internal wear in the pump, and you must shut down the machine immediately for inspection and repair.
Prevention is far better than repair; proper daily maintenance can significantly reduce failure rates:
Daily Inspection: Before starting work each day, be sure to check that the hydraulic oil level is within the normal range and inspect the entire vehicle for signs of oil leaks.
Regular Maintenance: Replace hydraulic oil (typically every 2,000 hours) and filters (return filter approximately every 500 hours) on schedule. When changing oil, be sure to use the same grade of oil; mixing different types is strictly prohibited. Note that using attachments such as hydraulic breakers accelerates oil contamination, so maintenance intervals must be shortened accordingly.
Safety First: Before performing maintenance, ensure the machine is parked on level ground, the bucket is lowered, and the engine is turned off. Wait until the system has completely cooled down before proceeding to prevent injury from hot oil spray.
The hydraulic system is the core of an excavator and is often quite complex. If you lack extensive operating experience, we recommend that after checking the basic items, you contact a professional technician to come on-site with diagnostic equipment for inspection. This approach is safer and more accurate.
