Bobcat T86 High-Flow/Super-Flow Valve Spool Solenoid Failure

Symptoms

• Inability to trigger auxiliary high flow rates from the joystick controllers
• Hydraulic attachment remains active when controls are released
• Engine lugging down or stalling when engine is turned on due to pressurized lines

Possible Causes

• Burnt proportional solenoid coil on the main hydraulic valve block
• Debris or silting jammed inside the pilot supply sliding spool valve
• Damaged solenoid electrical wiring harness running along the auxiliary frame

Diagnostic Procedure

1. 1
   Verify Auxiliary Flow Level Settings

   Turn on the loader. Access the in-cab display auxiliary setup screen. Confirm the flow level index is configured correctly for the attached equipment (Standard vs High-Flow vs Super-Flow scale).
2. 2
   Measure Proportional Solenoid Resistance

   Locate the Aux control valves on the main hydraulic block. Unplug the proportional valve solenoid coils. Measure resistance across the solenoid pins with a multimeter. A reading of 4.5 to 6.5 Ohms is standard. Any reading outside this range indicates an electrically damaged coil.
3. 3
   Check Solenoid Diagnostic Current Feed

   Connect Bobcat Service Analyzer. Monitor the driver current (Amps) sent to the aux solenoids while slowly rolling the joystick thumb wheel forward. Current should sweep smoothly from 0.5 Amps to 1.8 Amps. If current is missing or drops out, check the harness for a short or a failing cab controller driver.
4. 4
   Inspect Mechanical Valve Spool Operation

   Safely shut down the engine and relieve hydraulic line pressure. Carefully unscrew the proportional solenoid cartridge assembly. Inspect the sliding valve spool for metal shavings, deep scratches, or scoring. Clean out the valve bore with clean brake cleaner and verify the spool moves smoothly against spring pressure.

Common Repairs

• Replacing the proportional auxiliary hydraulic solenoid coil
• Polishing or replacing the sticky valve spool assembly
• Repairing the wiring harness to the main hydraulic block

Safety Precautions

• Release auxiliary pressure before starting service work by turning the ignition key to RUN and pressing the auxiliary pressure relief buttons.

Required Tools

• Digital Multimeter with current measurement capabilities
• High-fidelity hydraulic spanner socket set
• Bobcat Service Analyzer laptop

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Related Guides

Suggested Follow-Up Guides

• Bobcat T86 Hydraulic Control Valve Block Seal Replacement Guide
• Diagnosing Bobcat Joystick Controller Proportional Switch Failures
• How to Calibrate and Test Bobcat Super-Flow Hydraulic Pressures
• Bobcat D34 Engine Diagnostic Guide: Stalling Under Hydraulic Load
• Step-by-Step Electrical Harness Reconstruction for Bobcat T86 Auxiliary Valves

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