Bobcat 753G main belt tension failure and repair strategies

[MikePhua]

Summary
A Bobcat 753G skid steer with low operating hours may develop noise and performance issues due to aging of the main serpentine belt and malfunction of the internal clock-spring tensioner. Addressing this requires cleaning, inspection, and possibly replacing both the belt and tensioner assembly.
Machine background and production history
The Bobcat 753G is part of the 700-series skid steer loaders produced in the early 2000s by Bobcat Company, a division of Doosan Group. Bobcat pioneered the compact loader market in the 1960s and remains one of the most recognized brands in the industry. The 753G features a 43-horsepower Kubota diesel engine, vertical lift path, and a rated operating capacity of 1,300 lbs. It was widely adopted for landscaping, light construction, and agricultural use, with thousands of units sold across North America.
Symptoms of belt and tensioner failure
Operators may notice increased whining or squealing during startup or turning maneuvers. Upon inspection, the belt compartment may show signs of grease contamination, particularly around the fan pulley. The original belt, even if visually intact, may have internal cracking or dry rot after more than a decade of service.
Key indicators include:

• Greasy pulleys and belt surface
  
• Whining noise during movement or load
  
• Tensioner pointer stuck or misaligned
  
• Fan pulley fluid level slightly low
  
• Difficulty adjusting tensioner spring
  

In one case, the tensioner pointer was frozen near the 2:30 position, and attempts to adjust it with a pry bar and penetrating oil failed. The operator reinstalled the belt manually under tension, using a helper to tighten the hold bolt while applying force.
Understanding the clock-spring tensioner
The 753G uses a spring-loaded tensioner with an internal clock spring mechanism. This design maintains consistent belt tension as the belt stretches over time. However, if the spring seizes or the bearing binds on the tensioner frame, the system loses its self-adjusting capability.
To test the tensioner:

• Loosen the mounting bolt slightly
  
• Apply force with a pry bar to rotate the tensioner
  
• Tap the pulley with a hammer to shock the spring into motion
  
• Observe pointer movement and belt deflection
  

If the pointer remains immobile and the spring does not respond, the tensioner may need replacement.
Repair options and recommendations

• Replace the serpentine belt if cracks or dry rot are present, regardless of visual integrity
  
• Clean all pulleys with degreaser and inspect for bearing leaks
  
• Replace the tensioner assembly if spring action is lost
  
• Add a secondary spring to assist tension if OEM design proves insufficient
  
• Check fan pulley fluid level and top off if necessary
  

A technician reported that adding a light-to-medium tension assist spring helped maintain belt grip at high RPMs, preventing overheating caused by fan belt slippage.
Preventive maintenance tips

• Inspect belt and tensioner every 500 hours or annually
  
• Replace belt every 5 years regardless of hours
  
• Use OEM or high-quality aftermarket belts with proper length and profile
  
• Avoid overtightening the tensioner bolt, which can bind the spring
  
• Monitor fan pulley seals for slow leaks
  

Conclusion
The Bobcat 753G’s main belt system, while robust, is vulnerable to age-related degradation and tensioner failure. With proper inspection and timely replacement of components, operators can restore performance and avoid costly downtime. Understanding the interplay between belt condition, pulley alignment, and spring tension is key to maintaining this compact loader’s reliability.