FIFTH WHEEL CREEPS DOWNWARD

TM 9-2320-285-24-2

3-40. FIFTH WHEEL HYDRAULIC SYSTEM TROUBLESHOOTING (CONT)

MALFUNCTION

TEST OR INSPECTION

CORRECTIVE ACTION

3. FIFTH WHEEL CREEPS DOWNWARD

Step 1. Check if hydraulic control valve metering spool is in neutral position.

a. If metering spool is not in neutral position, repair hydraulic control valve or cable as required (para 3-42

c and 2-78a).

b. If metering spool is in neutral position, proceed to step 2 below.

Step 2. Lower fifth wheel boom fully.

Disconnect hose from bleed valve (para 2-87b(2)) and cap the hose and bleed valve.

Raise fifth wheel boom fully and check for downward creep.

a. If fifth wheel boom does not creep downward, bleed valve is defective; replace (para 2-78b(2)).

b. If fifth wheel boom creeps downward, lower fifth wheel boom fully, reconnect hose to bleed valve, and

proceed to step 3 below.

Step 3. Raise fifth wheel boom fully; support boom in raised position.

Disconnect two fifth wheel hydraulic cylinder hoses from the down-stroke ends of hydraulic cylinders (para

2-78b(2)) and cap the hoses.

Install a pressure gage in each hydraulic cylinder port.

Have an assistant pull back 5th WHEEL control lever fully; watch pressure gages.

a. If pressure gages indicate approximately zero psi and do not increase, hydraulic control valve is

leaking internally; repair or replace (para 3-42c).

b. If pressure gage indicates increased pressure, hydraulic cylinder is leaking internally; repair or replace

4. FIFTH WHEEL DOESN'T LOWER

Step 1. Check hydraulic cylinder rods for bent or jammed condition.

a. If hydraulic cylinder rods are bent or jammed, repair or replace cylinders (para 3-42d).

b. If hydraulic cylinder rods are not bent or jammed, proceed to step 2 below.

3-411