BOOM, ARM OR BUCKET CYLINDER EXTENDS OR CONTRACTS ITSELF AND BOOM, ARM OR BUCKET CYLINDER EXTENDS OR CONTRACTS ITSELF AND ATTACHMENT FALLS ATTACHMENT FALLS 3) 3) 5-19 YES Does the symptom change Normal when port relief valve is replaced YES with normal Is control valve valve? return spring Is not hydraulic NO YES normal? oil temperature high? NO Is genuine Abnormally high. hydraulic oil or equivalent being used? NO OK Disassemble and inspect check YES valve in hydraulic circuit and check for any fault. Is cylinder Abnormal internal leakage ⓐ within standard level? NO Cause Remedy Port relief valve is faulty. ⓐ Control valve's return spring is faulty.
Pressure tightness between control valve casing and spool is poor. Contact surface between poppet and seat is poor. Cylinder is faulty. Disassemble and repair or replace. Disassemble and replace. Locate the cause of hydraulic oil temperature rise and lower it to proper level. Replace with genuine hydraulic oil or equivalent. Disassemble and repair. Disassemble and repair. Disassemble and repair.