One-stop Solutions for Hydraulic Pump Wear, Weak Movement & Overheating

On mining and construction sites, large excavators from Komatsu, Hitachi and other brands frequently suffer issues including weak digging power, engine stalling, oil overheating and sluggish movements. Based on years of field maintenance data, over 80% of these malfunctions stem from internal wear and leakage of the hydraulic gear pump or main oil pump.

For equipment maintenance technicians, mine operation teams and construction procurement specialists, two major pain points persist: complicated fault diagnosis procedures, and expensive OEM hydraulic pumps with long lead times that lead to costly equipment downtime.

Drawing on practical maintenance experience from the Letpadaung Copper Mine in Myanmar, this article systematically explains the working principle of excavator hydraulic systems, standardized fault diagnosis workflows and solutions for four common malfunctions. It also introduces SDH hydraulic gear pumps by Shanghai Dazhong Hydraulic — a cost-effective drop-in replacement for imported pumps that fits diverse working conditions and cuts maintenance & component procurement costs.

1. Core Structure & Working Principle of Large Excavator Hydraulic Systems

Common large mining excavator models: Komatsu PC4000, PC2000, Hitachi EX1900, EX1200.

The hydraulic system acts as the power core of the machine, consisting of an engine, hydraulic gear pump (main working pump), control valve bank, pilot valve, swing & travel motors, hydraulic cylinders, safety relief valves, hydraulic oil tank and filter pipelines.

Power Transmission Flow

1. Hydraulic oil is drawn into the hydraulic pump via a filter at the bottom of the oil tank.
2. The pump pressurizes oil and delivers high-pressure fluid to parallel control valves.
3. Operators manipulate joysticks to activate pilot valves, switching oil circuits to control boom, arm, bucket, travel and swing motions.
4. A main safety valve regulates the overall system pressure, while individual branch safety valves provide overload protection for cylinders and motors.

The Critical Role of Hydraulic Gear Pumps

The hydraulic gear pump converts mechanical energy into hydraulic pressure energy. Subjected to continuous high pressure, dust and alternating impact loads, it is the fastest-wearing and most failure-prone component in the whole system.
Once pump wear, blocked oil suction or enlarged internal clearances occur, a chain of failures including weak power, overheating and abnormal noise will follow.

Hydraulic gear pumps are not exclusive to excavators. Municipal vehicles, agricultural machinery, metallurgical production lines and precision hydraulic power units all rely on them for power supply. Different working environments demand varying levels of wear resistance, high-temperature tolerance and sealing performance, so pump selection must match actual equipment operating conditions.

2. General Diagnosis & Maintenance Standards for Hydraulic Faults

✅ Three Core Principles for Troubleshooting

1. Identify the fault source first: Confirm whether the issue lies with the hydraulic system, engine or electrical circuit to avoid unnecessary pump disassembly.
2. Outside-in, simple-to-complex inspection: Check oil levels, filters and pipelines before dismantling delicate components like hydraulic pumps and valve banks.
3. Comprehensive multi-factor analysis: Do not simply replace the hydraulic pump without checking secondary issues such as faulty relief valves, sensors and clogged pipelines.

⚠️ 4 Mandatory Maintenance Rules

1. Never disassemble precision components including hydraulic gear pumps and main valves before completing full fault inspection.
2. Keep oil circuits and pump bodies spotless during maintenance. Only qualified anti-wear hydraulic oil can be used — impurities accelerate abrasion of gears and bushings.
3. Inspect mechanical and electrical faults simultaneously; replacing only hydraulic parts often leads to recurring failures.
4. Assemble pumps and seals correctly after replacement. Reverse installation or misconnected pipelines may cause pipe bursts and pressure overload.

3. Four Common Hydraulic Faults: Causes, Quick Diagnosis & Solutions

3.1 Weak Machine Movement (Slow Lifting / Travel / Swing)

① Weak performance when cold, normal after warming up

Fault sources: Main relief valve, unloading valve, internally worn hydraulic gear pump, PC-EPC valve, pilot valve, distributor oil seal
Solution: Test pump volumetric efficiency. If internal clearance exceeds the standard, replace with an SDH high-pressure gear pump. Its floating bushing self-compensation structure minimizes internal leakage during long-term operation, ideal for all mobile construction machinery.

② Weak performance when hot, normal when cold

Fault sources: Degraded hydraulic oil, high-temperature internal pump leakage, aging seals
Solution: Replace with new anti-wear hydraulic oil and upgrade to FKM high-temperature seals. For equipment operating continuously under high heat, select SDH heavy-duty high-flow gear pumps.

③ Weak travel or swing only

• Poor travel power: Engine overload, worn PC valve, abnormal travel motor relief pressure, insufficient main pump output pressure
• Poor swing power: Circuit connector failure, worn swing pump valve plate, internal pump pressure loss, damaged swing motor seals

④ Slow boom lifting

Fault sources: Clogged suction filter, internal cylinder leakage, stuck holding valve, insufficient tank oil, blocked relief valve
Maintenance tip: Replace suction filters regularly. SDH hydraulic pumps feature widened suction channels to eliminate cavitation and air ingestion.

3.2 Engine Lugging & Speed Drop During Operation

1. Mismatch between pump flow and engine power: Worn pumps output excessive flow and overload the engine. Replace with a gear pump of matched displacement for severe wear.
2. Clogged air intake or faulty turbocharger: Blocked air filters reduce intake volume and engine power. Conduct regular cleaning and maintenance.
3. Insufficient fuel supply under heavy load: Avoid prolonged full-load operation. SDH pumps with high volumetric efficiency cut useless energy consumption.
4. Aging and leaking components: Oil leaks from the engine or hydraulic pipelines reduce overall power. Inspect all leakage points comprehensively.

3.3 Excessively High Hydraulic Oil Temperature

Heat is generated in two key system sections: hydraulic gear pumps (mechanical-to-hydraulic energy conversion) and valve banks / cylinders (hydraulic-to-mechanical energy conversion).

Main overheating triggers:

1. Internal pump wear causing continuous heat generation from high-pressure leakage
2. Blocked oil cooler with poor heat dissipation
3. Relief valves staying open for sustained pressure release or heavily throttled pipelines

Optimization: Install long-lasting wear-resistant SDH hydraulic gear pumps, clean cooling systems regularly and calibrate relief pressure. Ideal for mining and metallurgical equipment running 24/7.

3.4 Abnormal Pump Noise & Rapid Bearing Damage

Fault triggers: Water-contaminated emulsified oil, filter breakdown letting impurities enter the pump, misaligned installation, dust/water ingress via damaged seals.

Optimization: All SDH gear pumps are fitted with self-lubricating DU composite bearings and dual dust-proof IP54 seals, greatly extending service life for outdoor, dusty construction and farm equipment.

4. 3 Universal On-site Fault Detection Methods

1. Pressure Gauge Testing (Most Widely Used)

Measure hydraulic pump output pressure with a pressure gauge. Low pressure generally indicates pump wear or defective relief valves. Flow rate can be roughly judged by cylinder movement speed, suitable for most on-site equipment inspections.

2. Visual & Tactile Manual Inspection (No Instruments Required)

• Visual check: Oil leaks or deformed pump housings & pipelines
• Tactile check: Pipeline vibration intensity reflects stable oil output pressure
• Auditory check: Air ingestion and internal wear produce sharp water hammer noise
• Olfactory check: Burnt odors signal overheating and cavitation, a key indicator for high-temperature working environments

3. Component Swap Diagnosis (For Remote Construction Sites)

Without professional testing equipment, remove the suspected faulty pump and test with a matching SDH hydraulic gear pump. If the fault disappears, the original pump is confirmed damaged — a fast diagnosis method for factory and field operations.

5. Long-term Maintenance Plan to Reduce Hydraulic Failures

1. Standardized Routine Servicing
   Replace hydraulic oil and all filters on schedule. Train technicians on pump disassembly, assembly and pressure calibration to avoid human-induced assembly faults.
2. Proactive Wear Prediction with Intelligent Testing
   Equip pressure & flow testers to detect early pump wear, enabling scheduled replacement before catastrophic failure and unplanned production shutdowns.
3. Establish Equipment Maintenance Logs
   Record pump replacement cycles and frequent fault types for every machine. Stock original SDH gear pumps, seals and bearings in bulk to drastically shorten downtime.

6. SDH Hydraulic Gear Pumps — Universal Drop-in Replacement for All Working Conditions

Original OEM hydraulic pumps suffer from rapid wear, high-temperature leakage, high purchase prices and long delivery lead times. SDH full-series gear pumps share identical mounting dimensions with European and Taiwanese imported pumps, enabling direct drop-in installation without pipeline modification.

Series Highlights & Application Characteristics

1. CBTT-F3 High-pressure Reinforced Gear Pump
   Max pressure up to 25MPa. Floating bushing clearance compensation maintains stable volumetric efficiency, perfect for frequently started mobile hydraulic machinery.
2. CBT-F5 Heavy-duty High-flow Gear Pump
   Wide suction channel, optional FKM high-temperature seals to withstand long-duration high-heavy-load operation and slow pump heat buildup & abrasion.
3. XP Multi-section Gear Pump
   Integrated 2/3-section coaxial design for multi-circuit synchronous oil supply. Saves installation space and eliminates leakage & shaft wear issues of split pump assemblies.
4. CBD-F1/F2 Micro Precision Gear Pump
   Compact size with low pressure pulsation, designed for small hydraulic power units and precision fixture clamping systems requiring low flow and high accuracy.
5. CBTs-F3 Economical Gear Pump
   Simple structure with low maintenance cost, suitable for light-to-medium load machinery balancing cost and durability.

Core Product Advantages

✅ Gears made of 20CrMnTi carburized and quenched alloy steel, hardness HRC58–62, high impact resistance and extended service life
✅ Symmetrical radial pressure relief grooves balance oil pressure, reduce spindle load and minimize abnormal noise & shaft breakage risks
✅ CE & ISO9001 dual certifications, direct replacement for imported pumps cutting procurement costs by over 60%
✅ Regional spare parts warehouses nationwide stock original seals and bearings for fast delivery, minimizing equipment downtime

7. Conclusion

The vast majority of hydraulic faults on large excavators stem from three root causes: internal hydraulic gear pump wear, clogged pipelines and degraded hydraulic oil. Follow the outside-in, simple-to-complex inspection logic to quickly resolve weak power, engine lugging, overheating and abnormal noise.

Hydraulic gear pumps act as the power heart of all hydraulic equipment, widely adopted in mining machinery, municipal sanitation vehicles, agricultural equipment, metallurgical and precision processing hydraulic stations. Pump quality directly determines equipment failure rates and annual maintenance expenses.

Two core strategies for long-term cost reduction and efficiency improvement:

1. Implement standardized daily maintenance to limit pump abrasion from dust, high temperatures and inferior hydraulic oil;
2. Adopt versatile, wear-resistant SDH hydraulic gear pumps as direct substitutes for imported components. Reliable domestic hydraulic power units reduce failure frequency and boost overall operational efficiency across all types of machinery.