Buzzing Warning And Performance Problems On A Bobcat 773 Skid Steer

[MikePhua]

Background Of The Bobcat 773 Skid Steer
The Bobcat 773 is a mid-size skid steer loader that, during its production run in the 1990s and early 2000s, became one of the most common compact loaders on the market. Bobcat as a brand essentially created the modern skid steer concept in the late 1950s and has since sold hundreds of thousands of machines worldwide. By the time the 773 series was in full production, annual global skid steer sales across all brands were in the tens of thousands, with Bobcat holding a major share thanks to strong dealer networks and a reputation for compact, maneuverable loaders.
The 773 sits in the “bread and butter” class of machines:

• Rated operating capacity typically around 1,700–1,800 lb
  
• Operating weight in the 2.7–3.0 ton range depending on options
  
• Hydrostatic drive with separate pumps for drive and loader functions
  
• Central hydraulic filter and several pressure and temperature switches feeding warning systems
  

Because these machines are used in everything from landscaping to construction to agriculture, they often accumulate many hours and see mixed maintenance quality. As a result, warning buzzers, fault codes and intermittent fuel issues are common topics in the life of a 773.
Buzzing Buzzer And Code HF1-2 Filter Restriction Warning
The first symptom in this case is a buzzer sounding and the display showing code HF1-2. On Bobcat 773 models, HF codes are associated with hydraulic filter conditions.
Key terms:

• Hydraulic filter restriction switch
  A pressure-sensitive switch in the hydraulic filter head that senses the pressure drop across the filter. When the filter starts to plug, the pressure difference increases. At a calibrated point, the switch closes and sends a signal to the controller, triggering a warning.
  
• First and second filters
  On many Bobcat loaders, the term “first filter” usually refers to the main hydraulic return or charge filter, while additional strainers or case drain filters may be considered secondary. The main service item for most owners is the large spin-on or cartridge filter in the hydraulic compartment.
  

With HF1-2 displayed, the system is essentially saying: “The primary hydraulic filter is highly restricted.”
A practical response sequence is:

• Open the engine door
  
• Locate the main hydraulic filter above and to the right of the engine (on many 773s)
  
• Replace the hydraulic filter with a correct-spec part
  
• Restart the machine and confirm whether the HF1-2 code and buzzing disappear
  

In the real case, changing the filter resolved the HF1-2 restriction warning, which confirms the filter really was restricted enough to trigger the switch.
Understanding The Switches On The Hydraulic Filter Head
The hydraulic filter head on machines like the 773 usually carries multiple sensors:

• Hydraulic temperature switch
  
• Hydraulic charge pressure switch
  
• Hydraulic filter restriction switch
  

They are typically threaded into the filter head and may appear similar externally, but they monitor different conditions.
Important terms:

• Hydraulic charge pressure
  The pressure that feeds the hydrostatic drive pumps and control valves. If it drops too low, the drive system will lose power or stop, and the machine may trigger alarms to protect components.
  
• Hydraulic temperature monitoring
  Prevents the system from running too hot, which can degrade oil and seals rapidly.
  
• Restriction sensing
  Protects pumps and valves from starvation caused by plugged filters.
  

Knowing which switch is which is crucial when tracing fault codes. Bobcat service information maps each code (such as HP3 or HF1-2) to a specific switch or sensor in this group.
Follow-Up Problem Code HP-3 Charge Pressure Switch And Wiring
After the filter change cleared HF1-2, a new code appeared: HP-3. The service manual explanation is that “wiring is not connected,” but in practice this usually points to an electrical issue related to the charge pressure switch.
Typical arrangement:

• Two main variants of the charge pressure switch
  • A screw-terminal type with two wires clamped under small screws
    
  • A molded, sealed connector type with a plug-in harness
    

Common failure modes:

• For the molded connector type
  • Oil can migrate through the switch body into the connector
    
  • When the cavity fills with oil, it can cause a false electrical reading, triggering codes like HP-3 even though hydraulic pressure is fine
    
• For the screw-terminal type
  • Loose or corroded connections at the screws
    
  • Broken or chafed wires near the terminals
    

Practical diagnostic steps:

• Identify which switch style is installed on the filter head
  
• If it has a molded plug
  • Unplug the connector and inspect for oil inside the plug
    
  • If oil is found, the switch is compromised and should be replaced
    
• If it has two screw terminals
  • Check for tight connections and clean corrosion
    
  • Gently tug the wires to see if any conductor is broken under the insulation
    

If mechanical wiring checks are fine but HP-3 persists, replacing the charge pressure switch is a relatively low-cost way to eliminate a common cause of the fault.
Enjoying The Learning Curve Doing Your Own Mechanics
The conversation around this kind of troubleshooting often includes a personal side: owners who bought skid steers primarily for work soon discover that learning to service them is practically a second trade. Tracking down codes, finding switches in cramped engine compartments, and puzzling through manuals can be frustrating, but there is also a sense of satisfaction.
In many owner-operator surveys, roughly 40–60% of small-machine owners perform at least basic maintenance and simple repairs themselves, motivated by:

• Cost control
  
• Limited dealer access in remote regions
  
• Personal interest and satisfaction
  

The Bobcat 773 is a good candidate for this kind of learning because:

• Parts are relatively accessible
  
• Documentation exists in both official and independent forms
  
• The basic hydrostatic and hydraulic architecture is robust and not overly complicated by modern electronics compared with newer machines
  

Hydraulic Work Tilt And Lift Spools Seals And O-Rings
At one stage, the owner replaced seals and O-rings in the tilt and lift spools. These spools are part of the main control valve that directs hydraulic oil to:

• Lift cylinders (raising and lowering the loader arms)
  
• Tilt cylinders (curling and dumping the bucket)
  

Over time, spool seals can harden, wear or become damaged by contamination. Symptoms include:

• Internal leakage causing slow creep of the loader arms or bucket when controls are neutral
  
• External leakage of oil around end caps
  
• Reduced responsiveness or erratic movements
  

Replacing these seals is a labor-intensive but straightforward job for someone comfortable with hydraulic components. It is also a good opportunity to inspect the valve block for:

• Scoring on spool surfaces
  
• Contaminant buildup
  
• Wear on linkage bushings
  

When combined with a fresh hydraulic filter and correct oil, this kind of work can noticeably tighten up a tired 773’s loader functions.
Hydraulic Leaks And Coupling Problems
After resolving earlier codes and restoring performance, a new issue appeared: leakage from a coupling. In the context of skid steers, “coupling” can refer to:

• A hydraulic quick coupler on auxiliary lines
  
• A drive coupling between engine and hydrostatic pump
  
• A hose-to-pipe connection in the hydraulic circuit
  

Given that the machine was worked and “felt powerful,” yet leakage appeared, the most likely culprit is a hydraulic fitting or hose connection disturbed during previous work. Typical corrective steps include:

• Cleaning the area thoroughly to remove oil and dirt
  
• Running the machine briefly to pinpoint the actual source
  
• Tightening or re-sealing the suspect fitting with the correct torque and thread sealant where applicable
  
• Replacing damaged hoses or O-rings
  

If the leak is at a shaft seal (such as a pump coupling seal), further disassembly will be required. Early attention is vital; hydraulic leaks waste oil, create slip hazards, and can lead to component damage if oil level drops too low.
New Symptom Engine Shutting Down And Fuel Primer Bulb Collapsing
Later, the skid steer developed a new behavior unrelated to the earlier buzzer and hydraulic issues. During work, the machine would shut down, and the operator noticed the fuel primer bulb (often called the “fuel ball”) being drawn inward, almost collapsing. After hand-pumping the bulb, the machine would run again for a while and then repeat the symptom.
This pattern points to a restriction on the fuel supply side.
Key terms:

• Fuel primer bulb
  A hand-operated rubber bulb that allows the operator to prime the fuel system by drawing fuel from the tank toward the engine. It should normally remain round or only slightly compressed while running.
  
• Fuel tank vent
  A small passage that allows air to enter the fuel tank as fuel is drawn out, preventing vacuum from building up.
  

When the engine runs and suction on the fuel line increases but air cannot enter the tank freely, vacuum develops. This vacuum:

• Collapses the primer bulb
  
• Starves the engine of fuel
  
• Causes the engine to shut down
  

Once the bulb is hand-pumped or the fuel cap is loosened, air rushes in, temporarily restoring flow.
Primary Causes Plugged Tank Vent Or Blocked Suction Screen
Two main causes were suggested:

• Plugged vent in the fuel cap
  • Modern caps typically incorporate a small vent valve or passage
    
  • Dirt, rust or dried fuel residue can block this vent
    
  • A quick test is to run the machine briefly with the fuel cap loosened; if the problem vanishes, the vent is suspect
    
• Plugged suction screen in the fuel tank
  • Many small loaders have a small screen or strainer inside the tank at the suction pickup
    
  • Over time, debris, rust and microbial growth (“diesel bugs”) can accumulate, partially blocking the screen
    
  • Under load, the engine draws fuel faster; the screen restriction increases suction, collapsing the primer bulb and starving the engine
    

Both causes are consistent with the observed symptom of the primer bulb sucking in and the machine dying after some running time.
Efficient Repair Strategy For Fuel Supply Issues
A practical, cost-effective repair sequence for this kind of fuel problem on a skid steer typically includes:

• Replace the fuel cap if the vent is suspect
  • Caps are relatively inexpensive and easy to swap
    
  • Ensures proper venting
    
• Service the fuel tank suction components
  • Obtain a new suction screen, clamps, hose and rubber grommet from the dealer
    
  • Commonly, the entire set of parts for this service might total around 20–25 units of local currency in materials, making it an inexpensive but impactful repair
    
• Drain and clean the tank
  • Remove the drain plug at the bottom of the tank
    
  • Drain several gallons of fuel, monitoring for debris, rust flakes or sludge
    
  • Replace the drain plug grommet with a fresh seal to avoid future leaks
    
• Replace the fuel filter and primer bulb
  • A collapsed or aged primer bulb may not recover well even after the underlying restriction is fixed
    
  • A fresh fuel filter ensures that new debris is not immediately drawn into the injection system
    

These steps address both immediate restriction and underlying contamination, restoring reliable fuel delivery.
Working In Remote Locations Parts And Self-Sufficiency
The owner in this case operated the machine in a small island nation, where dealer access and shipping times can be challenging. That reality highlights the value of:

• Keeping a small inventory of common service parts
  • Hydraulic filters and fuel filters
    
  • Primer bulbs and basic hoses
    
  • Common O-rings and seal kits for valves
    
• Building relationships with regional or international parts suppliers
  • To source genuine or high-quality aftermarket components at reasonable cost
    

For many small operators, shipping costs and delays can rival the price of the parts themselves. Being proactive about stocking wear items and learning to perform moderate repairs on a Bobcat 773 reduces downtime and dependency on distant shops.
A Short Story From The Yard Buzzers, Codes And A Clean Tank
Picture a contractor who bought a used Bobcat 773 to expand a small landscaping business. Work is busy, and maintenance has mostly meant “add fuel, grease it when remembered.” One day, during a tight schedule:

• A loud buzzer sounds, and an unfamiliar code flashes on the display
  
• After hurriedly consulting the manual, the owner realizes the hydraulic filter is restricted
  

With a new filter installed, the buzzer stops, but a new code appears. A helpful mechanic points out a small switch on the filter head, oozing oil into its connector. Replacing that switch clears the code.
Weeks later, just when everything seems solved, the engine starts quitting mid-job. The primer bulb is sucked flat every time. At first, the owner suspects the injection pump, but a more experienced hand suggests checking the fuel cap vent and tank screen. After draining several gallons of fuel and fishing out a mess of debris, plus installing a new primer bulb and filter, the 773 returns to reliable service.
In the process, the contractor gains not just a working machine but also a deeper understanding of its systems, along with the confidence to tackle future issues.
Preventive Measures To Reduce Recurring Problems
Real-world data from skid steer fleets show that a significant share of breakdowns are linked to neglected basic service items such as filters, fuel cleanliness and small electrical switches. A simple preventive plan for a Bobcat 773 can include:

• Regular hydraulic filter change
  • Follow hour-based intervals, often around 500 hours for return filters depending on application
    
  • Use quality filters to maintain proper flow and protection
    
• Periodic inspection of switches on the hydraulic filter head
  • Check for oil intrusion at molded connectors
    
  • Ensure wiring is supported and not chafing
    
• Routine fuel system maintenance
  • Replace fuel filters at manufacturer-recommended intervals or more often in dusty or humid conditions
    
  • Drain a small amount of fuel from the tank periodically to check for water and sediment
    
  • Once every year or two, inspect or replace the suction screen and clean the drain plug area
    
• Keeping the fuel cap vent clean
  • Replace caps that show obvious damage or vent blockage
    

These measures, combined with daily visual checks, can reduce unplanned downtime significantly.
Conclusion
A buzzing warning buzzer and a series of codes on a Bobcat 773 skid steer are not random annoyances; they are the machine’s early warning system for issues in the hydraulic and fuel systems. In this case:

• Code HF1-2 pointed to a genuinely restricted hydraulic filter
  
• Code HP-3 led to attention on the charge pressure switch and its wiring on the filter head
  
• Later, engine shutdowns with a collapsing primer bulb revealed fuel supply restrictions, likely tied to a plugged tank vent or suction screen
  

By systematically addressing each symptom—changing filters, inspecting switches, cleaning the fuel system and replacing inexpensive parts like primer bulbs and caps—an owner can restore a 773 to strong, dependable performance.
Beyond fixing one machine, the story underscores a broader lesson in skid steer ownership: many serious-looking problems can be solved through careful attention to filters, switches, vents and cleanliness, turning frustrating buzzers and shut-downs into manageable, even educational, maintenance tasks.