Hitachi EX200-5 Tracking Very Slow

[MikePhua]

Machine Background
The Hitachi EX200-5 is a mid-sized hydraulic excavator made by Hitachi Construction Machinery. It weighs about 18,800 kg (~41,400 lbs), has a standard bucket of ~0.8 cubic meters, and features a 6-cylinder Isuzu (A-6BG1T) engine with ~135 horsepower (~100 kW). The hydraulic system of the EX200-5 has multiple pumps (pppx2, gp x1), and travel/transport speed ranges up to about 5.5 km/h in high gear.
Because it's designed for digging, loading, and material handling, stable track speed and travel performance are essential. When the tracks slow down unpredictably, many tasks become inefficient or unsafe.

Terminology

• Tracking: Movement of the excavator along the ground via its tracks.
  
• Fast-track / High Travel Speed vs Low Travel Speed (“Slow Track”): Many machines have different travel modes (fast / high gear, slow / low gear). The terms refer to switching or operating in those different speeds.
  
• Drive pump / Travel motor: Hydraulic components that transmit fluid power to the travel motors (on each side) which turn the tracks.
  
• Speed sender / Throttle motor / Electronic Throttle: Sensors or motorized components that tell the ECM (engine control module) or control system how fast to run the engine and hydraulic pumps, or indicate the commanded speed.
  
• Distributor / Control Valve: Hydraulic distribution block that routes flow to travel motors, boom, etc.
  
• Wire harness / Electrical plug / Co-axial wire: Wiring components that carry signals for sensors or actuators. Any damage or bad connection can interrupt feedback or control signals.
  

Reported Symptoms

• Fast travel speed (“fast track”) stopped working.
  
• Machine sometimes alternates or “hunts” between regular speed and very slow.
  
• Occasional pulling to one side during travel.
  
• Some digging / work functions intermittently slow down to about ¾ speed, though mostly they operate normally.
  
• Tracking almost never works at full speed; the “slow track” becomes frequent.
  

Likely Causes
Based on these symptoms, the following are probable causes for slow or erratic tracking on the EX200-5:

• Bad electrical connections: A key user discovered that wires to plugs on the drive pump were brittle, had exposed portions, and some wires were touching (shorting) near the plug. These bad wiring conditions disrupted signals for speed or drive control.
  
• Faulty speed sender or throttle motor wiring: A co-axial wire connected to the speed sender was found bare; wires possibly shorted to ground (“earthing”), affecting the signal that dictates travel speed.
  
• Worn seals in hydraulic distributor or valves: Initially, seals in the distributor were badly worn (“in bits”), causing bad tracking behaviour (e.g. slow or erratic). Repair or replacement of those seals improved tracking, but the problem recurred over time as other issues emerged.
  
• Electrical signal intermittency: Because some digging functions also slowed sometimes, suggests the problem isn't purely mechanical, but involves control signals or feedback loops that affect multiple systems.
  

Data & Spec Support

• Travel speed spec is about 5.5 km/h in high mode.
  
• Engine power ~ 135 hp (~100-kW) must match hydraulic pump flow and signal inputs for proper travel performance. If throttling or signal is disrupted, machine won’t reach full travel speed.
  

Troubleshooting Steps

1. Inspect wiring at the drive pump and speed sender
   • Remove or expose the plugs near the drive pump; look for brittle insulation, exposed wires, corrosion, or wires touching each other.
     
   • Check the co-ax cable to the speed sensor/sender. If the insulation is damaged (“bare”), repair or replace.
     
   • Check any grounding (“earthing”) issues that may allow signal bleed or shorts.
     
2. Seal and valve inspection
   • Remove and inspect the distributor / control valve associated with track travel. If seals are worn or torn, they should be replaced.
     
   • Check for internal leakage in travel control valves: if fluid bypasses or leaks internally, track speed will drop or become slow under load.
     
3. Test electrical signals
   • With multimeter or diagnostics tools, monitor the speed sender output during operation. See if the output corresponds to commanded speed.
     
   • Check throttle motor input/output signals: if throttle cannot open fully due to signal loss, hydraulic pump may not get full power.
     
4. Check hydraulic pressure and pump condition
   • Measure actual hydraulic pressure under travel load; compare to manufacturer’s spec.
     
   • Inspect pumps for wear, internal damage, or slipping. If flow or pressure is low, track speed will suffer.
     
5. Check track / undercarriage condition
   • Too much friction from worn or binding rollers, tension too tight, or damaged links may slow down travel.
     
   • Examine if machine is “pulling to one side” – could mean one travel motor or final drive is weaker or leaking.
     

Solutions

• Replace or repair damaged wiring: new conduit, insulating sleeving, correct wiring connection, ensure no shorts.
  
• Replace worn seals in the travel distributor / valves. Use OEM or equivalent quality seals; ensure correct seal materials (resistance to pressure, heat).
  
• If speed sender or throttle motor is defective, replace or recalibrate. Ensure connectors are clean, terminals tight.
  
• Pump overhaul if pressure / flow is significantly below spec.
  
• Adjust track tension according to spec to avoid drag.
  
• Regular preventive maintenance: check electrical connections, inspect seals, maintain hydraulic fluid cleanliness, monitor travel speed over time for trends.
  

Real-World Story
One owner of an EX200-5 with ~16,000 hours and many operators experienced exactly these symptoms: fast travel (“fast track”) stopped, then intermittent slow travel, pulling to one side, digging functions occasionally sluggish. After digging through electrical wires, found the coaxial wire to speed sender had exposed conductor and wires to throttle motor were shorting (“earthing”). After repairing wiring, insulating, replacing the seal in the distributor, tracking returned to normal for several days. But over time, the “slow track” problem began creeping back, more frequently. This suggested the seals, while temporarily repaired, may not have been replaced with highest durability types, or other wear remained (e.g. distributor, pump internals).

Prevention & Best Practices

• Schedule regular inspections of wiring around pump and sensors. Exposed wires often come from vibration, chafing, or rodent damage. Use protective conduits.
  
• Replace distributor / valve seals proactively if travel control starts to fade. Do not wait until failure.
  
• Keep hydraulic fluid clean, use proper filtration, and inspect for signs of contamination or varnish that may affect valve slippage.
  
• Monitor travel speed regularly. If machine begins to “hunt” or lag, note hours since last major rebuild—it may indicate wear in pump, control valve, or motors.
  
• Ensure undercarriage parts (rollers, sprockets, final drives) are well maintained; excessive friction or drag can mask electrical or hydraulic problems.
  

Conclusion
The EX200-5 “tracking very slow” issue usually arises from a combination of worn hydraulic seals and compromised electrical connections (speed sender, throttle wiring). Although initial fixes like replacing a seal or repairing wires can restore performance, these often are only partial fixes unless wear in related hydraulic or mechanical components is addressed. Consistent preventive maintenance—especially of electrical harnesses, sensors, and hydraulic system integrity—can keep the machine tracking properly and avoid frustrating intermittent slow travel.