Resolving Jerky Hydraulic Movement on the Bobcat 335 Excavator

[MikePhua]

The Bobcat 335 and Its Compact Excavator Profile
The Bobcat 335 is a mid-sized compact excavator introduced in the early 2000s, designed for trenching, grading, and light demolition. With an operating weight of approximately 7,800 lbs and a digging depth of nearly 12 feet, the 335 balances power and maneuverability for contractors working in urban and residential environments. Bobcat Company, founded in 1947 and headquartered in North Dakota, has sold thousands of 300-series excavators globally, with the 335 gaining popularity for its responsive hydraulics and robust undercarriage.
Despite its reputation for agility, some operators report jerky hydraulic behavior even at low operating hours. This issue can compromise precision, increase wear on components, and frustrate operators transitioning from other Bobcat machines with smoother control profiles.
Terminology Annotation

• Pilot Pressure: Low-pressure hydraulic signal used to actuate main control valves.
  
• Slew Function: The rotational movement of the upper structure of the excavator.
  
• Feathering: Fine control of hydraulic functions for smooth, gradual movement.
  
• Hydraulic Spool Valve: A component that directs fluid flow to specific actuators based on joystick input.
  

Symptoms of Jerky Hydraulics
Operators may experience:

• Abrupt or twitchy boom and stick movement
  
• Difficulty feathering controls for precise grading
  
• Sudden stops or surges during slewing
  
• Bucket shaking when attempting to clean or dislodge material
  
• Inconsistent response between functions, especially at low RPM
  

In one landscaping crew in Oregon, a Bobcat 335 with only 300 hours exhibited jerky boom lift and thumb actuation. The operator, accustomed to the smoother response of an S750 skid-steer, found the excavator difficult to control during tree planting and trailer loading.
Root Causes and Diagnostic Strategy
Jerky hydraulics can stem from several factors:

• Excessive pilot pressure causing overreaction to joystick input
  
• Air in the hydraulic system leading to spongy or erratic behavior
  
• Contaminated or degraded hydraulic fluid affecting valve response
  
• Sticky spool valves or worn seals in the control block
  
• Miscalibrated flow control or relief settings
  

Recommended diagnostic steps:

• Check pilot pressure against factory spec (typically 400–600 psi)
  
• Bleed the hydraulic system to remove trapped air
  
• Inspect fluid for contamination, discoloration, or water intrusion
  
• Test joystick response and valve actuation under load
  
• Verify slew gear backlash and confirm absence of slew brake (not present on 300-series)
  

In one service bay in Alberta, a technician resolved jerky movement by adjusting pilot pressure down by 50 psi and replacing a sticky boom spool valve. The machine regained smooth control and improved operator confidence.
Adjustment and Repair Solutions
To improve hydraulic smoothness:

• Adjust pilot pressure using the regulator near the control valve block
  
• Replace hydraulic fluid and filters with OEM-specified grade
  
• Clean or rebuild spool valves showing signs of sticking or wear
  
• Install joystick dampers or restrictors to reduce input sensitivity
  
• Upgrade to newer joystick assemblies with improved modulation
  

For slewing issues:

• Accept minor backlash due to lack of slew brake in older models
  
• Inspect slew motor and gear teeth for wear or excessive clearance
  
• Avoid abrupt stops during rotation to minimize gear shock
  

In one excavation firm in Georgia, operators were trained to modulate joystick input and avoid sudden reversals. This reduced hydraulic shock and extended cylinder seal life by 30%.
Preventive Maintenance and Operator Tips

• Warm up hydraulic system for 5–10 minutes before full operation
  
• Grease all pivot points weekly to reduce mechanical resistance
  
• Monitor fluid temperature and avoid prolonged high-RPM operation
  
• Clean control valve block and inspect for debris or corrosion
  
• Practice feathering techniques during low-load tasks
  

Operators transitioning from skid-steers or loaders may need time to adapt to excavator control dynamics. In one training session, a Bobcat dealer used simulator drills to teach feathering and coordinated movement, improving operator finesse and reducing jerky behavior.
Final Thoughts
The Bobcat 335 is a capable compact excavator, but its hydraulic responsiveness can feel abrupt without proper calibration and operator technique. With attention to pilot pressure, fluid quality, and valve condition, the machine can deliver smooth, precise control even at low hours. Whether planting trees, trenching utilities, or grading pads, the 335 proves that finesse is just a few adjustments away.
In hydraulics, control is confidence. And when the movement flows clean and steady, the job follows suit.