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The Bobcat 743 and Its Mechanical Legacy
The Bobcat 743 skid steer loader, introduced in the early 1980s, was part of Bobcat’s push to dominate the compact equipment market. With a rated operating capacity of around 1,300 pounds and powered by a 36-horsepower Kubota diesel engine, the 743 became a staple on construction sites, farms, and landscaping projects. Its hydraulic system drives both the lift and tilt functions of the loader arms and bucket, making it essential for material handling and grading.
The 743 uses a gear-driven hydraulic pump and a series of control valves to direct fluid to the lift and tilt cylinders. The system is relatively simple by modern standards but requires precise operation and maintenance to avoid performance issues.
Symptoms of Hydraulic Failure and Initial Observations
A common issue reported by operators is the sudden loss of hydraulic function after the machine has been parked for a period. In one case, the bucket would raise slowly to about two feet and then stop, while the tilt function only allowed dumping but not retraction. The machine still moved forward and backward normally, indicating that the drive hydraulics were unaffected.
The hydraulic fluid level was checked and found to be adequate, though a steady drip was observed from the auxiliary hydraulic line during operation. This leak, combined with the machine sitting idle for weeks, raised concerns about air infiltration or valve malfunction.
Auxiliary Hydraulic Engagement and Its Impact
One overlooked cause of hydraulic dysfunction in the Bobcat 743 is the accidental engagement of the auxiliary hydraulic circuit. When the auxiliary hydraulics are engaged without an attachment connected, the system diverts flow away from the lift and tilt functions. This results in partial or no movement of the loader arms and bucket.
To disengage the auxiliary circuit:
Preventive Measures and Mechanical Safeguards
To prevent accidental engagement of the auxiliary hydraulics:
Hydraulic Warning Lights and Filter Maintenance
Another issue observed in older Bobcat 743 models is the hydraulic warning light staying illuminated at idle. This can indicate low fluid pressure or a clogged hydraulic filter. If the light turns off at higher RPMs but remains on at idle, the filter should be replaced.
Steps to address this:
Conclusion
Hydraulic issues on the Bobcat 743 often stem from simple causes like auxiliary circuit engagement or neglected maintenance. By understanding the system’s layout and behavior, operators can quickly diagnose and resolve problems without resorting to costly repairs. The 743 remains a reliable workhorse, and with proper care, its hydraulic system can deliver consistent performance for decades.
The Bobcat 743 skid steer loader, introduced in the early 1980s, was part of Bobcat’s push to dominate the compact equipment market. With a rated operating capacity of around 1,300 pounds and powered by a 36-horsepower Kubota diesel engine, the 743 became a staple on construction sites, farms, and landscaping projects. Its hydraulic system drives both the lift and tilt functions of the loader arms and bucket, making it essential for material handling and grading.
The 743 uses a gear-driven hydraulic pump and a series of control valves to direct fluid to the lift and tilt cylinders. The system is relatively simple by modern standards but requires precise operation and maintenance to avoid performance issues.
Symptoms of Hydraulic Failure and Initial Observations
A common issue reported by operators is the sudden loss of hydraulic function after the machine has been parked for a period. In one case, the bucket would raise slowly to about two feet and then stop, while the tilt function only allowed dumping but not retraction. The machine still moved forward and backward normally, indicating that the drive hydraulics were unaffected.
The hydraulic fluid level was checked and found to be adequate, though a steady drip was observed from the auxiliary hydraulic line during operation. This leak, combined with the machine sitting idle for weeks, raised concerns about air infiltration or valve malfunction.
Auxiliary Hydraulic Engagement and Its Impact
One overlooked cause of hydraulic dysfunction in the Bobcat 743 is the accidental engagement of the auxiliary hydraulic circuit. When the auxiliary hydraulics are engaged without an attachment connected, the system diverts flow away from the lift and tilt functions. This results in partial or no movement of the loader arms and bucket.
To disengage the auxiliary circuit:
- Locate the right-hand control lever inside the cab.
- Pull the lever toward the center of the cab to reset its position.
- Confirm that the auxiliary valve is no longer active by observing full function return to the lift and tilt controls.
Preventive Measures and Mechanical Safeguards
To prevent accidental engagement of the auxiliary hydraulics:
- Insert a 3/8-inch bolt into the locking hole located at the base of the right-hand stick.
- This mechanical lockout prevents the lever from being moved unintentionally.
- The bolt may require lifting the cab to access, depending on the machine’s configuration.
Hydraulic Warning Lights and Filter Maintenance
Another issue observed in older Bobcat 743 models is the hydraulic warning light staying illuminated at idle. This can indicate low fluid pressure or a clogged hydraulic filter. If the light turns off at higher RPMs but remains on at idle, the filter should be replaced.
Steps to address this:
- Replace the hydraulic filter with an OEM or high-quality aftermarket unit.
- Fill the new filter partially with hydraulic fluid before installation to prevent air pockets.
- After installation, run the machine at idle and monitor the warning light.
- If the light persists, inspect for leaks or pressure loss in the system.
Conclusion
Hydraulic issues on the Bobcat 743 often stem from simple causes like auxiliary circuit engagement or neglected maintenance. By understanding the system’s layout and behavior, operators can quickly diagnose and resolve problems without resorting to costly repairs. The 743 remains a reliable workhorse, and with proper care, its hydraulic system can deliver consistent performance for decades.
