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The EX320L Excavator and Its Legacy
The Caterpillar EX320L is part of the 320 series of hydraulic excavators, a line that helped define mid-sized earthmoving equipment in the 1990s and early 2000s. Built for versatility in construction, mining, and infrastructure development, the EX320L features a long undercarriage (denoted by the “L”) for improved stability during digging and lifting operations. Its operating weight hovers around 44,000 pounds, and it typically pairs with a bucket capacity of 1.2 to 1.5 cubic yards.
Powering this particular unit is the Caterpillar 3116 engine—a 6-cylinder, turbocharged diesel engine introduced in the late 1980s. Rated at approximately 170 horsepower, the 3116 was designed for medium-duty applications and became a staple in both on-road and off-road machinery. Though later replaced by the 3126 and C7 engines, the 3116 remains widely used in legacy fleets across Africa, Asia, and South America due to its mechanical simplicity and parts availability.
Caterpillar Inc., founded in 1925, has sold millions of excavators globally. The 320 series alone has seen tens of thousands of units deployed, with the EX320L being particularly favored in developing markets for its durability and ease of repair.
Symptoms of Travel Dysfunction
In this case, the machine exhibits sluggish movement on the right track when viewed from the operator’s cabin. All implement functions—boom, stick, and bucket—operate normally, suggesting that the primary hydraulic pumps are functioning. However, the right-side travel motor struggles even on level ground, indicating a localized issue in the travel circuit.
Initial troubleshooting steps included:
Terminology Annotation
One overlooked diagnostic method is the case drain flow test. This test measures internal leakage from hydraulic motors and can reveal worn seals, damaged bearings, or excessive bypass. If a travel motor has high case drain flow, it may lack sufficient torque to propel the track.
In this scenario, the operator lacked access to a pressure gauge due to equipment damage en route to the job site. However, without case drain data, it’s difficult to rule out internal leakage in the motor or swivel.
A similar case occurred in Kenya, where an excavator exhibited weak travel on one side. After extensive part swapping, a technician performed a case drain test and discovered that the motor was bypassing fluid internally. Replacing the motor resolved the issue—highlighting the importance of this diagnostic step.
Swivel Rebuild Considerations
Rebuilding the swivel requires careful attention to seal placement and housing condition. Corrosion, pitting, or improper reassembly can lead to cross-port leakage, where fluid intended for one circuit bleeds into another. This can cause erratic travel behavior or pressure loss.
During reassembly:
Pilot Control and Valve Integrity
The travel function is controlled by pilot pressure transmitted through foot pedal valves. Swapping these valves is a valid test, but if pilot hoses have been tampered with or misrouted, control signals may be delayed or weakened.
Recommendations include:
Crossover Valve Compatibility
Some excavators use crossover relief valves to protect travel motors from pressure spikes. These valves are often side-specific due to flow characteristics and mounting orientation. Swapping incompatible valves can lead to uneven travel or hydraulic lock.
Before swapping:
The final drive contains planetary gears that multiply torque from the travel motor. While gear condition appeared normal in this case, it’s worth noting that worn bearings or misaligned gears can cause drag. A full teardown should include:
The sluggish right track on the Caterpillar EX320L likely stems from a hydraulic imbalance rather than mechanical failure. While motor swapping and swivel rebuilding are valid steps, the absence of case drain testing leaves a diagnostic gap. Pilot hose integrity, valve compatibility, and swivel sealing must be verified before deeper disassembly.
This case underscores the importance of methodical troubleshooting and the value of pressure data. In remote regions where diagnostic tools are scarce, technicians must rely on procedural discipline and mechanical intuition. With proper testing and attention to hydraulic detail, even elusive travel faults can be resolved—restoring the machine to full operational strength.
The Caterpillar EX320L is part of the 320 series of hydraulic excavators, a line that helped define mid-sized earthmoving equipment in the 1990s and early 2000s. Built for versatility in construction, mining, and infrastructure development, the EX320L features a long undercarriage (denoted by the “L”) for improved stability during digging and lifting operations. Its operating weight hovers around 44,000 pounds, and it typically pairs with a bucket capacity of 1.2 to 1.5 cubic yards.
Powering this particular unit is the Caterpillar 3116 engine—a 6-cylinder, turbocharged diesel engine introduced in the late 1980s. Rated at approximately 170 horsepower, the 3116 was designed for medium-duty applications and became a staple in both on-road and off-road machinery. Though later replaced by the 3126 and C7 engines, the 3116 remains widely used in legacy fleets across Africa, Asia, and South America due to its mechanical simplicity and parts availability.
Caterpillar Inc., founded in 1925, has sold millions of excavators globally. The 320 series alone has seen tens of thousands of units deployed, with the EX320L being particularly favored in developing markets for its durability and ease of repair.
Symptoms of Travel Dysfunction
In this case, the machine exhibits sluggish movement on the right track when viewed from the operator’s cabin. All implement functions—boom, stick, and bucket—operate normally, suggesting that the primary hydraulic pumps are functioning. However, the right-side travel motor struggles even on level ground, indicating a localized issue in the travel circuit.
Initial troubleshooting steps included:
- Swapping the left and right travel motors
- Rebuilding the hydraulic swivel (center joint)
- Interchanging foot pedal valves
- Inspecting planetary gears in the final drive
Terminology Annotation
- Travel Motor: A hydraulic motor that drives the tracks of an excavator.
- Swivel (Center Joint): A rotating hydraulic coupling that allows fluid to pass between the upper and lower structures of the excavator.
- Case Drain: A low-pressure return line that allows internal leakage from hydraulic components to flow back to the tank.
- Pilot Hoses: Small-diameter hydraulic lines that transmit control signals to valves and actuators.
One overlooked diagnostic method is the case drain flow test. This test measures internal leakage from hydraulic motors and can reveal worn seals, damaged bearings, or excessive bypass. If a travel motor has high case drain flow, it may lack sufficient torque to propel the track.
In this scenario, the operator lacked access to a pressure gauge due to equipment damage en route to the job site. However, without case drain data, it’s difficult to rule out internal leakage in the motor or swivel.
A similar case occurred in Kenya, where an excavator exhibited weak travel on one side. After extensive part swapping, a technician performed a case drain test and discovered that the motor was bypassing fluid internally. Replacing the motor resolved the issue—highlighting the importance of this diagnostic step.
Swivel Rebuild Considerations
Rebuilding the swivel requires careful attention to seal placement and housing condition. Corrosion, pitting, or improper reassembly can lead to cross-port leakage, where fluid intended for one circuit bleeds into another. This can cause erratic travel behavior or pressure loss.
During reassembly:
- Inspect spindle surfaces for scoring or rust
- Use OEM seal kits and follow torque specifications
- Pressure test the swivel after installation
Pilot Control and Valve Integrity
The travel function is controlled by pilot pressure transmitted through foot pedal valves. Swapping these valves is a valid test, but if pilot hoses have been tampered with or misrouted, control signals may be delayed or weakened.
Recommendations include:
- Verifying pilot hose routing against factory schematics
- Checking for kinks, leaks, or contamination
- Measuring pilot pressure at the valve block during travel commands
Crossover Valve Compatibility
Some excavators use crossover relief valves to protect travel motors from pressure spikes. These valves are often side-specific due to flow characteristics and mounting orientation. Swapping incompatible valves can lead to uneven travel or hydraulic lock.
Before swapping:
- Confirm part numbers and flow ratings
- Inspect valve seats and springs for wear
- Test relief pressure using a calibrated gauge
The final drive contains planetary gears that multiply torque from the travel motor. While gear condition appeared normal in this case, it’s worth noting that worn bearings or misaligned gears can cause drag. A full teardown should include:
- Checking backlash and gear mesh
- Inspecting bearing races for pitting
- Measuring shaft runout
The sluggish right track on the Caterpillar EX320L likely stems from a hydraulic imbalance rather than mechanical failure. While motor swapping and swivel rebuilding are valid steps, the absence of case drain testing leaves a diagnostic gap. Pilot hose integrity, valve compatibility, and swivel sealing must be verified before deeper disassembly.
This case underscores the importance of methodical troubleshooting and the value of pressure data. In remote regions where diagnostic tools are scarce, technicians must rely on procedural discipline and mechanical intuition. With proper testing and attention to hydraulic detail, even elusive travel faults can be resolved—restoring the machine to full operational strength.
We sell 3 types：
1. Brand-new excavators.
2. Refurbished excavators for rental business, in bulk.
3. Excavators sold by original owners
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1. Brand-new excavators.
2. Refurbished excavators for rental business, in bulk.
3. Excavators sold by original owners
https://www.facebook.com/ExcavatorSalesman
https://www.youtube.com/@ExcavatorSalesman
Whatsapp/Line: +66989793448 Wechat: waji8243
