HYDRAULIC AR 1096424 - Caterpillar

Introduction
Moving the bucket from an OPEN to CLOSED position under certain operating conditions can cause the bucket cylinder to void. The usual symptom is that the bucket hesitates or falls open when digging.This test determines a cause for bucket cylinder voiding. 1. Check for bucket cylinder voiding when operating bucket CLOSE.a. Increase the hydraulic system to normal operating temperature.b. Set the engine speed dial at position 10 with the AEC switch in the OFF position.c. Place the power mode selector switch in MODE III.d. Position stick and boom so that the stick is nearly parallel to the ground.e. Move the bucket pilot control lever to the full OPEN position (bucket cylinder fully retracted).f. Quickly move the bucket pilot control lever to the bucket CLOSE position.g. When the bucket reaches the bottom of its arc, measure the amount of time the bucket pauses before continuing. Expected Result:Bucket pause time should be no more than 2 seconds at the bottom of the bucket arc. Results:* OK - Bucket pause time is less than 2 seconds. STOP.* NOT OK - Bucket pause time is greater than 2 seconds. Proceed to Step 2.2. Check operation of bucket cylinder head end makeup valve.a. Stop the engine and release the pressure in the hydraulic system. Refer to "Release Of Pressure In The Hydraulic System", Form SENR6187.
Main Control Valve
(1) Relief valve (bucket cylinder head end).b. Remove bucket cylinder head end line relief valve (1) and visually inspect the makeup valve for sticking or not opening. The makeup valve is in combination with the line relief valve. Expected Result:Bucket cylinder makeup valve moves freely. Results:* OK - Proceed to Step 3.* NOT OK - Repair sticking makeup valve. If makeup valve cannot be repaired and main valve is damaged beyond repair, the basic control valve which houses the makeup valve will require replacement. STOP.3. Perform Control Valve Shift Pressure Test. For further information refer to the section, "Control Valve Shift Pressure Test". Results:* OK - Proceed to Step 4.* REPAIRED, OK - STOP.4. Perform Return Line Pressure Test. For further information refer to the section, "Return Line Pressure Test". Results:* OK - Cause for problem not found with this test. The test equipment may be faulty, a repair may have been made incorrectly, or an error may have been made during the diagnosis of this problem. Check to determine whether or not the problem is still present. If it is, repeat test procedure. STOP.* REPAIRED, OK - STOP.