Kobelco’s SK115SR and Its Compact Excavator Legacy
The Kobelco SK115SR was introduced during the mid-2000s as part of Kobelco’s Short Radius (SR) series, designed for urban and confined job sites. Kobelco Construction Machinery, a division of Kobe Steel founded in 1905, had long been a pioneer in hydraulic excavator technology. The SK115SR featured a compact tail swing, advanced hydraulic circuitry, and a reputation for smooth multi-function operation. By 2007, Kobelco had sold tens of thousands of SR-series units globally, especially in North America and Southeast Asia, where tight access and fuel efficiency were critical.
The SK115SR is powered by a 4-cylinder diesel engine paired with a load-sensing hydraulic system. Its arm (or stick) is controlled via pilot-operated joysticks that actuate proportional control valves, feeding fluid to the boom, arm, and bucket cylinders. When the arm becomes stuck in the fully extended position, it suggests a failure in either hydraulic control, mechanical interference, or internal cylinder damage.
Terminology Clarification

• Arm/stick: The second section of the excavator’s digging implement, connected between the boom and bucket.
  
• Pilot control: A low-pressure hydraulic signal used to actuate main control valves.
  
• Cylinder gland: The threaded collar at the end of a hydraulic cylinder that retains the rod and seals.
  
• Barrel: The main body of the hydraulic cylinder where the piston travels.
  
• Spool valve: A sliding valve inside the control block that directs hydraulic flow.
  

• Check pilot pressure at the arm control port
  
• Inspect pilot lines for damage or disconnection
  
• Remove and inspect the arm spool for scoring or contamination
  
• Test solenoid function if electronically actuated
  

• Shut down the machine
  
• Bleed pilot pressure manually
  
• Disconnect the arm cylinder lines and test for flow
  
• Use a manual valve override if available
  

• Replace hydraulic filters every 500 hours
  
• Use ISO 46 hydraulic fluid in temperate climates, ISO 32 in cold regions
  
• Inspect cylinder glands for thread wear and torque annually
  
• Flush pilot lines during major service intervals
  
• Install magnetic plugs in valve blocks to catch debris
  

Introduction
The Komatsu D31 series dozers are renowned for their durability and versatility in various construction and forestry applications. However, like any heavy machinery, they are susceptible to certain issues that can affect performance and productivity. Understanding these common problems and their solutions can help operators and maintenance personnel keep the equipment running efficiently.
Hydraulic Steering Failures
One of the most prevalent issues with the Komatsu D31 dozers is hydraulic steering failure. Operators have reported instances where the machine becomes difficult to steer or completely unresponsive to steering inputs. This problem is often linked to low or contaminated hydraulic fluid, which can lead to a loss of pressure in the steering system. Regularly checking fluid levels and replacing contaminated fluid can mitigate this issue. Additionally, inspecting the steering cylinder for damage or blockage and ensuring the control valve operates smoothly without obstruction are crucial steps in maintaining steering functionality.
Transmission and Drive System Issues
Another common problem involves the transmission and drive system. Operators have experienced situations where the dozer fails to move under load or exhibits delayed engagement in forward or reverse gears. These symptoms often indicate issues such as low hydraulic pressure, contaminated fluid, or worn components within the transmission system. Regular maintenance, including fluid changes and filter replacements, can help prevent these problems. In some cases, inspecting and replacing the transmission filter may resolve the issue.
Engine Overheating
Engine overheating is another concern reported by D31 dozer operators. Possible causes include a malfunctioning thermostat, blocked radiator fins, or issues within the cooling system. For instance, a faulty water pump impeller can cause inadequate coolant circulation, leading to overheating. Regularly checking the radiator for blockages and ensuring the cooling system is functioning properly can help prevent overheating. Using a temperature gun to check the temperature difference between the upper and lower radiator hoses can also aid in diagnosing circulation issues.
Steering Clutch Problems
Steering clutch issues are frequently encountered, especially in older models. Symptoms include the pedals not returning after being pressed or the machine failing to turn as expected. These problems are often due to worn or damaged steering clutches, which may require replacement. In some cases, after prolonged inactivity, the steering clutches may become sticky or unresponsive, necessitating thorough inspection and servicing.
Final Drive and Bevel Gear Wear
The final drive and bevel gears are critical components in the D31 dozer's drivetrain. Over time, these parts can experience wear, especially if the machine has been operated in harsh conditions. Operators have reported issues such as delayed reverse gear engagement, which can be indicative of wear in the bevel gears. Regularly inspecting these components and replacing worn parts can help maintain the dozer's performance.
Conclusion
While the Komatsu D31 dozers are robust machines, they are not immune to common issues that can affect their performance. Regular maintenance, including checking hydraulic fluid levels, inspecting the steering and transmission systems, monitoring engine temperature, and servicing the final drive components, can help prevent these problems. By staying proactive with maintenance, operators can ensure the longevity and reliability of their Komatsu D31 dozers.

The Legacy of Funk Manufacturing and the Reversomatic Line
Funk Manufacturing, founded in the early 20th century in Coffeyville, Kansas, built its reputation on durable transmissions for agricultural and industrial equipment. By the 1960s, Funk had become a go-to supplier for OEMs needing rugged, torque-rich gearboxes. Their Reversomatic transmission series was designed specifically for applications requiring shuttle shift capability—such as drill rigs, loaders, and forestry machines—where frequent forward-reverse transitions are essential.
The Reversomatic system integrates a torque converter with a shuttle clutch pack, allowing smooth directional changes without manual clutching. This design became popular in Texoma drill rigs and other utility platforms throughout North America. While Funk was eventually acquired by John Deere Power Systems, their transmissions remain in service decades later, often outlasting the machines they were installed in.
Terminology Clarification

• Torque converter: A fluid coupling between the engine and transmission that multiplies torque and allows slippage at low speeds.
  
• Shuttle clutch: A hydraulic clutch pack that enables forward and reverse gear engagement.
  
• Governor: A device that regulates engine or hydraulic system speed based on load or RPM.
  
• Linkage: Mechanical connections between control levers and transmission components.
  
• Break-in procedure: A controlled operating period after rebuild to seat components and ensure proper lubrication.
  

• Low hydraulic pressure due to worn pump or clogged filters
  
• Faulty governor not allowing sufficient modulation at higher RPMs
  
• Incorrect fluid viscosity or contamination
  
• Internal leakage in clutch packs or converter housing
  
• Misadjusted or binding control linkage
  

• Worn stator bearings
  
• Cracked turbine fins
  
• Damaged one-way clutch
  
• Improper clearance between impeller and turbine
  

• Verify fluid type and temperature suitability
  
• Inspect and clean hydraulic filters and screens
  
• Test governor operation and replace if necessary
  
• Measure hydraulic pressure at clutch ports during engagement
  
• Confirm torque converter rebuild quality and internal clearances
  
• Check linkage travel and spool valve seating
  

Introduction
For those venturing into the world of excavation, selecting the right machine is paramount. An excavator equipped with auxiliary hydraulics can significantly enhance versatility and productivity. This guide delves into the importance of auxiliary hydraulics, considerations when purchasing, and tips for maximizing their potential.
Understanding Auxiliary Hydraulics
Auxiliary hydraulics refer to a secondary hydraulic system that delivers pressurized fluid from the main pump to operate various attachments on an excavator. This system allows the machine to power tools such as hydraulic hammers, grapples, augers, and thumbs, transforming it into a multifunctional asset on the job site. Not all excavators come standard with this feature; hence, it's essential to verify its presence when considering a purchase.
Benefits of Auxiliary Hydraulics

• Increased Versatility: Enables the use of a wide range of attachments, making the excavator suitable for various tasks beyond digging.
  
• Enhanced Productivity: Hydraulic attachments often operate more efficiently than manual tools, leading to faster completion of tasks.
  
• Improved Safety: Reduces the need for manual handling, minimizing the risk of operator fatigue and injury.
  
• Cost Efficiency: Investing in a single machine capable of multiple functions can reduce the need for additional equipment and labor.
  

• Attachment Compatibility: Ensure the excavator's hydraulic system matches the requirements of the intended attachments, including flow rate and pressure specifications.
  
• Flow Rate Options: Excavators may offer standard or high-flow auxiliary hydraulics. High-flow systems provide greater power for demanding attachments but may come at a higher cost.
  
• Circuit Type: Determine whether the system is single-acting (flow in one direction) or double-acting (flow in both directions), depending on the attachments' needs.
  
• Control System: Modern excavators often feature proportional control valves, allowing for precise adjustment of hydraulic flow to attachments.
  

Kubota’s SVL90-2 and Its Role in Compact Track Loader Evolution
Kubota’s SVL90-2 compact track loader was introduced as part of the company’s aggressive expansion into the North American construction market in the early 2010s. Kubota, founded in 1890 in Osaka, Japan, had long been known for its agricultural equipment, but the SVL series marked a turning point in its commitment to heavy construction. The SVL90-2, with a rated operating capacity of 2,800 lbs and a breakout force exceeding 7,000 lbs, quickly became a favorite among contractors for its reliability, hydraulic power, and operator comfort.
By 2015, Kubota had sold tens of thousands of SVL units across North America, with the SVL90-2 often deployed for land clearing, grading, and brush cutting. However, like any hydraulic machine, it’s not immune to wear, contamination, or control valve issues—especially when lift arms begin to drift or fail to hold position.
Terminology Clarification

• Lift arms: The hydraulic arms that raise and lower the loader bucket or attachment.
  
• Relief valve: A hydraulic component that limits pressure to prevent damage; often adjustable.
  
• Spool valve: A directional control valve that routes hydraulic fluid to actuators.
  
• Joystick spool: The internal valve mechanism controlled by the operator’s joystick.
  
• Centering spring: A spring that returns the spool to neutral when the joystick is released.
  

• Raised the boom and curled the bucket down to lift the front of the machine. The boom held firm.
  
• Lowered the boom and curled the bucket to lift the front again. The bucket held firm.
  

• Internal leakage in the lift cylinders due to worn piston seals
  
• Faulty relief cartridges in the control valve block
  
• Spool valve leakage or misalignment
  
• Debris obstructing valve seats or drain passages
  
• Pilot pressure anomalies keeping the valve slightly open
  

• Debris lodged in the seat area
  
• Damaged or unravelled makeup valve springs
  
• Worn seals or scoring on the valve body
  

• Test cylinder integrity by lifting the machine and observing drift
  
• Inspect and clean relief cartridges, noting thread positions
  
• Swap cartridges to isolate faults
  
• Check joystick spool centering springs and drain passages
  
• Maintain fluid cleanliness and replace filters regularly
  

Introduction
The Caterpillar AP1000 asphalt paver is a widely used machine in the construction industry, known for its efficiency and reliability. However, like any complex piece of machinery, it is not immune to operational challenges. Operators and technicians have reported several recurring issues that can impact performance. Understanding these problems and their potential solutions is crucial for maintaining optimal functionality and minimizing downtime.
Electric Screed Heating Problems
One of the most frequently reported issues with the AP1000 involves the electric screed heating system. Operators have noted that the screed takes an unusually long time to heat up, sometimes up to an hour, even in moderate temperatures. Additionally, the "heating up" and "hot" indicator lights often flash continuously, indicating a potential malfunction. In some cases, these issues persist despite updates to the wiring harness and replacement of heating elements.
Hydraulic System Cavitation
Another common problem is hydraulic system cavitation. Operators have reported that after several hours of use, the hydraulic pumps begin to cavitate, leading to a loss of power and responsiveness. This issue is often accompanied by difficulty steering the machine, even at low speeds. The cause is typically traced back to air entering the hydraulic system, which can result from suction leaks, low fluid levels, or contamination.
Steering Difficulties
Steering issues are also prevalent among AP1000 users. Operators have experienced extremely hard steering, making maneuvering the paver challenging. This problem is often linked to hydraulic system cavitation or insufficient hydraulic fluid, which affects the servo control valves responsible for steering.
Troubleshooting and Solutions
To address these issues, several steps can be taken:

• Screed Heating: Ensure that the heating elements are functioning correctly and that the heating chambers are clean and free from old asphalt and debris. Regular maintenance and inspections can help prevent overheating and ensure consistent performance.
  
• Hydraulic System: Regularly check for suction leaks and ensure that hydraulic fluid levels are adequate. Inspect filters for contamination and replace them as necessary. Testing the servo solenoid valves and adjusting them to allow sufficient oil flow can also help mitigate cavitation issues.
  
• Steering: Monitor hydraulic fluid temperature to prevent it from reaching boiling points, which can cause air bubbles and affect steering performance. Installing an adequate oil cooler and ensuring that the computer systems are not overheating can prevent steering difficulties.
  

The Case 580 Series and Its Enduring Utility
The Case 580 backhoe loader has been a cornerstone of construction and municipal fleets since its introduction in the 1960s. Manufactured by J.I. Case, a company founded in 1842, the 580 series evolved through multiple generations—B, C, D, E, K, L, M—each refining hydraulic performance, operator comfort, and structural durability. By the early 2000s, Case had sold hundreds of thousands of 580 units globally, making it one of the most recognizable and widely used backhoes in the world.
Despite its rugged design, decades of exposure to moisture, salt, and vibration inevitably lead to corrosion—especially in the cab floor and fender assemblies. Rebuilding these areas is often more complex than it appears, especially when working with limited equipment and salvaged materials.
Terminology Clarification

• Cab floor: The steel base beneath the operator’s seat and controls, often housing inspection plates and linkage access.
  
• Fender: The curved metal panel over the rear wheels, protecting the cab from mud and debris.
  
• Flux core wire: A type of welding wire that contains flux, allowing welding without external shielding gas.
  
• Plasma cutter: A tool that uses ionized gas to cut through metal with precision.
  
• Inspection plate: A removable panel that allows access to internal components like brake linkages or hydraulic lines.
  

• 1/8" steel plate for the floor
  
• 16-gauge sheet metal for the fenders
  
• 2"x1/4" flat bar for the floor lip
  
• 1"x1" square tubing for door sills
  
• 2" L-bracket (1/4" thick) for subfloor supports
  

• A 120V Lincoln MIG welder with 0.035 flux core wire
  
• A Powermax 30 plasma cutter
  
• A single angle grinder
  
• A car trunk scissor jack
  

Introduction
The John Deere 992ELC and the Hitachi EX400-3 are both formidable hydraulic excavators designed for heavy-duty applications in construction, mining, and forestry. While John Deere manufactures its own line of excavators, it has a longstanding collaboration with Hitachi, leading to shared components and design similarities between certain models. This article delves into the parts interchangeability between the 992ELC and EX400-3, providing insights for operators and maintenance professionals.
Background on John Deere and Hitachi Excavators
John Deere's foray into hydraulic excavators began in the 1970s, with the company establishing a partnership with Hitachi in the 1980s to enhance its product offerings. This collaboration resulted in the development of models like the 992ELC, which shares many components with Hitachi's EX400 series. Such partnerships have allowed both companies to leverage each other's strengths, leading to machines that combine Deere's engineering with Hitachi's hydraulic expertise.
Key Components with Shared Part Numbers
Several critical components are interchangeable between the 992ELC and EX400-3, highlighting the synergy between the two models:

• Hydraulic Oil Cooler: Part number 4333473 is compatible with both the 992ELC and EX400-3, ensuring efficient cooling of hydraulic fluids.
  
• Idler Pulley: The front idler pulley, part number 9134295, fits both models, contributing to the smooth operation of the undercarriage.
  
• Bucket Pin: Part number 8039138 is used in both excavators, facilitating secure attachment of the bucket to the linkage.
  
• Bushing 3026075: This bushing is compatible with both models, playing a vital role in the articulation of the boom and arm.
  
• Angle Sensor: Part numbers 4716888 and AT154533 are used in both excavators, providing critical feedback for the machine's control system.
  

• Model Variations: Ensure that the part number matches the specific model and serial number of your machine, as variations can exist within the same model series.
  
• OEM vs. Aftermarket: Original Equipment Manufacturer (OEM) parts are recommended for optimal performance and longevity, though high-quality aftermarket parts can be considered for cost savings.
  
• Component Condition: When replacing parts, assess the condition of related components to prevent premature wear and ensure overall machine reliability.
  

• Regular Inspections: Conduct routine checks for wear, leaks, and damage to critical components.
  
• Timely Replacements: Replace worn or damaged parts promptly to prevent further damage and costly repairs.
  
• Proper Lubrication: Ensure that moving parts are adequately lubricated to reduce friction and wear.
  

Introduction
The Kobelco SK160 excavator is a versatile and reliable machine widely used in construction and excavation projects. Equipped with advanced hydraulic systems, it offers efficient performance and precise control. However, in certain situations, such as system malfunctions or emergencies, operators may need to engage manual override functions to maintain control and continue operations. Understanding the location and operation of manual override screws is crucial for ensuring the excavator's functionality in such scenarios.
Understanding Manual Override Functions
Manual override functions are designed to provide operators with alternative means of control when the primary electronic or hydraulic systems fail or become unresponsive. These functions allow for basic machine movements, enabling operators to reposition the equipment or perform essential tasks until full system functionality is restored. In the Kobelco SK160 excavator, manual override screws are integral components that facilitate this backup control.
Locating the Manual Override Screws
The manual override screws on the Kobelco SK160 excavator are typically situated on the pump regulator assembly. These screws are designed to adjust the displacement of the hydraulic pumps manually, allowing for basic machine operation. To locate them:

1. Access the Engine Compartment: Open the engine compartment to gain access to the hydraulic pump area.
   
2. Identify the Pump Regulator: Locate the pump regulator assembly, which is usually positioned near the main hydraulic pumps.
   
3. Find the Manual Override Screws: Look for two screws labeled as "Manual Override" or "Back-up" screws. These are typically small, with a 4.5mm head size.
   
4. Loosen the Lock Nuts: Before adjusting the screws, loosen the 13mm lock nuts that secure them in place.
   
5. Adjust the Screws: Turn the manual override screws counterclockwise to increase pump displacement, allowing for manual operation. Ensure both screws are adjusted equally to maintain balanced hydraulic flow.
   

1. Start the Engine: Turn on the engine and allow it to reach idle speed.
   
2. Engage Manual Controls: Use the joystick or control levers to operate the excavator. Movement may be slower and less responsive than usual, but basic functions should be operational.
   
3. Monitor System Performance: Keep an eye on the hydraulic pressure gauges and listen for any unusual noises, indicating potential issues.
   
4. Limit Operations: Perform only essential tasks to prevent overloading the manual system.
   

1. Return to Engine Compartment: Access the engine compartment once more.
   
2. Adjust Manual Override Screws: Turn the manual override screws clockwise to return the pumps to their normal variable displacement mode.
   
3. Tighten Lock Nuts: Secure the screws by tightening the 13mm lock nuts.
   
4. Test the System: Start the engine and test the excavator's functions to ensure full system restoration.
   

• Regular Inspection: Periodically check the manual override screws for wear or damage.
  
• Avoid Overuse: Manual override should be used only in emergencies or when troubleshooting.
  
• Professional Assistance: If issues persist after manual operation, consult a certified Kobelco technician for further diagnosis and repair.
  

Introduction
The Bobcat 751 skid steer loader, introduced in the late 1980s, is a compact yet powerful machine renowned for its versatility and reliability. Over the years, it has become a staple in various industries, from construction to landscaping. However, like all machinery, it requires regular maintenance to ensure optimal performance. One critical component that often needs attention is the hydraulic system, particularly the hydraulic line running from the pump to the filter. This article provides a comprehensive guide on replacing this hydraulic line, addressing common challenges, and offering practical solutions.
Understanding the Hydraulic System
The hydraulic system in the Bobcat 751 is responsible for powering various functions, including lifting, tilting, and auxiliary operations. The hydraulic line from the pump to the filter plays a crucial role in maintaining the cleanliness and efficiency of the hydraulic fluid, which is vital for the system's performance. Over time, this line can become worn, leading to leaks or reduced efficiency.
Common Issues with the Hydraulic Line

1. Leaks and Contamination: The most prevalent issue is leakage, often caused by wear or damage to the hydraulic line. This can lead to contamination of the hydraulic fluid, compromising the system's performance.
   
2. Clogging: Debris or contaminants can accumulate in the hydraulic line, leading to blockages that restrict fluid flow and reduce system efficiency.
   
3. Wear and Tear: Continuous operation can cause the hydraulic line to degrade, leading to cracks or breaks that necessitate replacement.
   

1. Preparation: Before beginning the replacement process, ensure the machine is on a level surface, and the engine is turned off. Engage the parking brake to prevent any unintended movement.
   
2. Accessing the Hydraulic Line: Depending on the specific model and configuration, you may need to remove certain components to access the hydraulic line. This could include the filter mounting block or other obstructing parts. Use appropriate tools to carefully remove these components without causing damage.
   
3. Disconnecting the Old Line: Using suitable wrenches or socket sets, disconnect the old hydraulic line from both the pump and the filter. Be prepared for residual hydraulic fluid to leak out; have a container ready to catch any spillage.
   
4. Installing the New Line: Position the new hydraulic line in place, ensuring it matches the routing of the old line to avoid interference with other components. Connect the new line to both the pump and the filter, tightening the fittings securely without over-torquing.
   
5. Reassembly: Reinstall any components that were removed to access the hydraulic line. Ensure all fasteners are tightened to the manufacturer's specifications.
   
6. Testing: Start the engine and operate the hydraulic functions to check for proper operation. Inspect the new hydraulic line for any signs of leaks or issues.
   

• Limited Access: In some configurations, access to the hydraulic line can be restricted. In such cases, removing the exhaust manifold, fan, or other components may be necessary to gain sufficient access. Always refer to the service manual for specific guidance.
  
• Stubborn Fittings: Corroded or tight fittings can be challenging to remove. Applying penetrating oil and allowing it to sit for a period can help loosen these fittings. Using a crow's foot wrench or a short socket can provide the necessary leverage in tight spaces.
  
• Hydraulic Fluid Spillage: To minimize spillage, have absorbent materials on hand to catch any leaks. Properly dispose of any used hydraulic fluid in accordance with local regulations.
  

• Regular Inspections: Periodically check the hydraulic lines for signs of wear, leaks, or damage. Addressing issues early can prevent more significant problems down the line.
  
• Use Quality Components: Always use OEM (Original Equipment Manufacturer) parts or high-quality aftermarket components to ensure compatibility and reliability.
  
• Proper Fluid Maintenance: Regularly change the hydraulic fluid and filter to maintain system cleanliness and efficiency.