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Understanding the Case 680E and Its Air Brake System
The Case 680E tractor-loader-backhoe was introduced in the early 1980s as part of Case Corporation’s push to modernize its earthmoving equipment lineup. Building on the success of the 680CK, the 680E featured improved hydraulics, a more robust frame, and notably, an air brake system—a rarity among mid-sized backhoes of its time. Case, founded in 1842, had long been a pioneer in agricultural and construction machinery, and by the 1980s, its equipment was being exported globally, with the 680 series selling tens of thousands of units across North America, Europe, and Asia.
The air brake system on the 680E was designed to offer better stopping power and reliability, especially in heavy-duty applications. However, as these machines aged, operators began reporting issues with brake responsiveness, particularly when the machine was in gear. This article explores the underlying causes, adjustment procedures, and real-world anecdotes that shed light on maintaining optimal brake performance.
Symptoms of Brake Failure Under Load
One common issue reported by operators is that the brakes work adequately when the machine is in neutral but fail to stop it effectively when in gear. This discrepancy often points to insufficient brake force being applied, which can be caused by several factors:
S-Cam Brakes and Their Adjustment
The Case 680E uses S-cam brakes, a type commonly found in heavy trucks and some construction equipment. The “S-cam” refers to the S-shaped camshaft that rotates to push the brake shoes against the drum. Proper adjustment of these brakes is critical to ensure full contact and effective stopping power.
Adjustment involves rotating the slack adjuster to reduce the clearance between the brake shoes and drum. However, if the linings are excessively worn, adjustment alone won’t restore braking performance. In such cases, replacement of the linings is necessary. Operators should also inspect for oil contamination, which can drastically reduce friction and lead to brake fade.
Terminology Notes
The air compressor is the heart of the brake system, supplying pressurized air to the reservoirs. If the compressor belt is loose, glazed, or slipping, it may not generate adequate pressure. Additionally, the governor must be set correctly to allow the system to reach full operating pressure—typically between 100 to 125 psi. If the governor cuts off too early, the system may never reach sufficient pressure, leading to weak braking.
A retired operator from Georgia once shared that his machine’s governor was cutting off at 90 psi, well below the recommended threshold. After adjusting the governor, the brakes regained their stopping power, highlighting the importance of pressure regulation.
Leak Detection and Maintenance Tips
To identify leaks, operators should listen for hissing sounds when applying the brakes or parking brake. Common leak points include:
In Illinois, a seasoned mechanic recalled a 680E that consistently lost air pressure during operation. After a thorough inspection, he discovered a hairline crack in the actuator diaphragm that only leaked under pressure. Replacing the actuator resolved the issue, and the machine returned to full service.
Modern Comparisons and Legacy
While newer backhoes have largely transitioned to hydraulic braking systems, the air brake setup on the Case 680E remains a testament to the engineering of its era. Its design borrowed heavily from highway truck systems, making parts more accessible and repairs more familiar to mechanics with trucking experience.
Today, vintage Case machines like the 680E are still in use across farms, small construction firms, and municipal yards. Their longevity is a tribute to Case’s build quality and the adaptability of their components. However, maintaining these machines requires a blend of mechanical intuition and historical knowledge—skills that are becoming rarer as newer generations move toward digital diagnostics.
Conclusion
Air brake adjustment on the Case 680E is not merely a matter of turning a wrench—it’s a diagnostic journey that involves understanding pressure dynamics, mechanical wear, and system integrity. By combining proper adjustment techniques with vigilant maintenance and historical awareness, operators can ensure these classic machines continue to perform safely and reliably.
The Case 680E tractor-loader-backhoe was introduced in the early 1980s as part of Case Corporation’s push to modernize its earthmoving equipment lineup. Building on the success of the 680CK, the 680E featured improved hydraulics, a more robust frame, and notably, an air brake system—a rarity among mid-sized backhoes of its time. Case, founded in 1842, had long been a pioneer in agricultural and construction machinery, and by the 1980s, its equipment was being exported globally, with the 680 series selling tens of thousands of units across North America, Europe, and Asia.
The air brake system on the 680E was designed to offer better stopping power and reliability, especially in heavy-duty applications. However, as these machines aged, operators began reporting issues with brake responsiveness, particularly when the machine was in gear. This article explores the underlying causes, adjustment procedures, and real-world anecdotes that shed light on maintaining optimal brake performance.
Symptoms of Brake Failure Under Load
One common issue reported by operators is that the brakes work adequately when the machine is in neutral but fail to stop it effectively when in gear. This discrepancy often points to insufficient brake force being applied, which can be caused by several factors:
- Worn brake linings that reduce friction
- Air leaks in the brake lines or actuators
- Improper brake adjustment
- Contaminants such as differential oil on the brake surfaces
- Weak air compressor output or faulty governor settings
S-Cam Brakes and Their Adjustment
The Case 680E uses S-cam brakes, a type commonly found in heavy trucks and some construction equipment. The “S-cam” refers to the S-shaped camshaft that rotates to push the brake shoes against the drum. Proper adjustment of these brakes is critical to ensure full contact and effective stopping power.
Adjustment involves rotating the slack adjuster to reduce the clearance between the brake shoes and drum. However, if the linings are excessively worn, adjustment alone won’t restore braking performance. In such cases, replacement of the linings is necessary. Operators should also inspect for oil contamination, which can drastically reduce friction and lead to brake fade.
Terminology Notes
- Slack Adjuster: A mechanical lever that adjusts the distance between the brake shoes and drum.
- Actuator: A device that converts air pressure into mechanical force to apply the brakes.
- Governor: A component that regulates the air compressor’s cut-in and cut-out pressure levels.
- S-Cam: A camshaft shaped like an “S” that spreads the brake shoes when rotated.
The air compressor is the heart of the brake system, supplying pressurized air to the reservoirs. If the compressor belt is loose, glazed, or slipping, it may not generate adequate pressure. Additionally, the governor must be set correctly to allow the system to reach full operating pressure—typically between 100 to 125 psi. If the governor cuts off too early, the system may never reach sufficient pressure, leading to weak braking.
A retired operator from Georgia once shared that his machine’s governor was cutting off at 90 psi, well below the recommended threshold. After adjusting the governor, the brakes regained their stopping power, highlighting the importance of pressure regulation.
Leak Detection and Maintenance Tips
To identify leaks, operators should listen for hissing sounds when applying the brakes or parking brake. Common leak points include:
- Brake chambers
- Air lines and fittings
- Parking brake valve
- Compressor discharge line
- Checking compressor belt tension and condition
- Inspecting air lines for cracks or wear
- Testing the governor cut-in and cut-out pressures
- Verifying slack adjuster positions
- Inspecting brake linings for wear or contamination
In Illinois, a seasoned mechanic recalled a 680E that consistently lost air pressure during operation. After a thorough inspection, he discovered a hairline crack in the actuator diaphragm that only leaked under pressure. Replacing the actuator resolved the issue, and the machine returned to full service.
Modern Comparisons and Legacy
While newer backhoes have largely transitioned to hydraulic braking systems, the air brake setup on the Case 680E remains a testament to the engineering of its era. Its design borrowed heavily from highway truck systems, making parts more accessible and repairs more familiar to mechanics with trucking experience.
Today, vintage Case machines like the 680E are still in use across farms, small construction firms, and municipal yards. Their longevity is a tribute to Case’s build quality and the adaptability of their components. However, maintaining these machines requires a blend of mechanical intuition and historical knowledge—skills that are becoming rarer as newer generations move toward digital diagnostics.
Conclusion
Air brake adjustment on the Case 680E is not merely a matter of turning a wrench—it’s a diagnostic journey that involves understanding pressure dynamics, mechanical wear, and system integrity. By combining proper adjustment techniques with vigilant maintenance and historical awareness, operators can ensure these classic machines continue to perform safely and reliably.
