Hydraulic motors. Titan PowrTwin 4900 | 6900 | 8900 | 12000 Plus, PowrTwin 4900, 6900, 8900, 12000 Plus Service Manual

GB

Troubleshooting

3.3 Hydraulic Motors

Problem

A. Oil motor stalls at bottom (no unusual heat problems)

B. Oil motor stalls at top (no unusual heat problems)

D. Low pressure (both strokes - high heat)

Note: Engine labors at stall on both strokes.

Cause

1. Fluid pump piston seat unthreaded

2. Valve sticking or oil motor trip rod shifter assembly separated

1. Valve sticking

2. Broken spring retainer (valve rod assembly)

3. Broken spring or valve rod

4. Air in hydraulic motor

5. Air in fluid pump

C. Low pressure (okay on down stroke, sluggish on up.stroke — high heat)

1. Blown piston seal

Note: Engine labors on upstroke, idles back at stall on the down stroke.

2. Cracked piston

1. Blown center o-rings on spool valve

2. Bad hydraulic pump

Solution

1. If connecting rod is okay, remove cylinder head plug and pop valve down. Replace plug and start machine.

If machine cycles up and stops at bottom again, then problem is piston seat on fluid pump. Check piston seat.

Repair or replace as necessary. If piston seat is okay and problem does not change, check oil motor.

2. Remove valve and check for scratches and rough movement when sliding it up and down. Replace valve and spool in this condition. Check trip rod for possible separation.and spool in this condition. Check trip rod for possible separation.

1. Remove valve and check for scratches and rough movement when sliding it up and down. Replace valve and spool in this condition.

2. Replace valve rod assembly.

3. Replace valve rod assembly.

4. Reset valve. Purge Air, generally accomplished by low pressure cycling of motor/pump assembly for 5–10 minutes. Check for causes of air introduction:

• Loose fittings in tank.

• Loose fittings on hydraulic pump.

• Loose hose connections.

• Low oil in reservoir.

5. Stall at top can occur randomly when fluid pump picks up air. Reset valve. Avoid air in the fluid pump.

1. Before dismantling oil motor, start machine. With pump cycling under pressure, touch the hydraulic cylinder and the head to see if cylinder or head gets hotter. This will help determine if piston seal is blown or piston nut is broken. If heat is on the head, check the o-rings on spool valve.

2. Dismantle oil motor and check piston seals cylinder bore and piston nut. Pay special attention to piston nut. It can be cracked and not show externally.

1. Before dismantling oil motor, start machine. With pump cycling under pressure, touch the head to see if the head becomes hotter. This will help determine if center o-ring is blown on spool valve. If hot, remove and replace o-ring.

2. Replace hydraulic pump.

14 PowrTwin Plus