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Bobcat T86 Low Hydrostatic Drive Charge Pressure Diagnostic
Bobcat·T86·Bobcat D34·Intermediate·1-2 hours·0 views
The Bobcat T86 exhibits tracking shudder or sluggish dynamic responses under load. The machine drives slowly, tracks unevenly to one side, and the warning alert sounds periodically, indicating low drive charge pressure.
Symptoms
- A low-pitch hydraulic whining noise when attempting path steering
- The red charge pressure warning light illuminates under full engine load
- Slow track-motor acceleration response or delayed drive engagement
Possible Causes
- Severely restricted or blocked hydrostatic drive oil filter element
- Worn-out primary charge pump (located inside the main tandem pump assembly)
- Stuck open or drifting hydrostatic charge pressure relief valve cartridge
Diagnostic Procedure
- 1Review Hydrostatic Charge Filter HistoryInspect the maintenance logs. If the charge pressure hydraulic filter has been in place for more than 500 hours, replace it as a baseline action. Remove and cut open the old filter media to inspect for bronze particles or steel shards indicating internal pump damage.
- 2Install Diagnostic Hydraulic Pressure GaugeLocate the dedicated hydrostatic charge pressure test gauge port (usually located on the side of the tandem pump housing). Connect a 1,000 PSI liquid-filled pressure gauge using a standard zero-leak diagnostic coupler.
- 3Measure Charge Pressure Under Various SpeedsStart the engine and run at low idle. The charge oil pressure should hold steadily above 350 PSI. Rev the engine up to full throttle (approx. 2400 RPM). The charge pressure should rise and stabilize between 380 PSI and 420 PSI. If pressure drops severely below 300 PSI under load, proceed with diagnostic analysis.
- 4Inspect and Test Charge Relief ValveRemove the hydrostatic charge pressure system relief valve cartridge. Clean and inspect the internal spring and seat for dynamic wear, metal contaminants holding the spool open, or a broken internal spring. Reinstall, adjust, or replace as indicated.
Common Repairs
- Replacing the hydrostatic charge system filter cartridge
- Replacing the main hydrostatic pump charge section
- Replacing or shimming the charge system relief valve cartridge
Safety Precautions
- Place the loader securely on heavy ground blocks or safety concrete pillars, as tracks may unexpectedly rotate during pressure tests.
- Ensure hydraulic oil reservoir pressure is fully exhausted before connecting pressure gauges.
Required Tools
- 1,000 PSI premium liquid-filled pressure gauge
- Hydrostatic Quick-coupler test adapters
- Hydraulic oil collection recovery basin
Related Fault Codes
M0206 (Low Charge Pressure Fault)M0207 (Charge pressure critical limit reached)D5060 (Tandem Pump Performance Derate)
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Suggested Follow-Up Guides
- Bobcat T86 Hydrostatic Charge Pressure Relief Valve Testing and Replacement
- Bobcat D34 Engine Hydraulic Pump Drive Coupler Inspection and Repair
- Bobcat T86 Tandem Pump Flow and Pressure Isolation Procedures
- How to Diagnose and Rebuild Bobcat T86 High-Flow Hydraulic Control Valves
- Bobcat Track Loader Drive Motor Flushing and Contamination Management Guide
Topics
Bobcat T86 hydrostatic pressure troubleshootingBobcat M0206 fault code diagnosticBobcat T86 low charge pressureBobcat tandem pump performance derateBobcat M0207 code troubleshootingBobcat T86 hydraulic whine diagnosticsBobcat T86 hydrostatic drive pressure testBobcat D5060 fault codeBobcat track motor delayed engagementBobcat T86 hydraulic charge pressure specBobcat D34 low hydraulic pressure under load
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