OIL 1053335 - Caterpillar

Possible Defects in the Hydraulic System
Make reference to S on first page of the TESTING AND ADJUSTING Section.
1. Always attach pressure gauges at the individual test points. Observe the necessary measuring ranges for each of the test points.2. Proceed systematically, i.e. using the hydraulic circuit diagram, formulate hypothetical causes and carry out logical pressure measurements several times.1. A pump or one side of a valve bank has insufficient output or none at all: Reverse the two pressure hoses on the pump. If the symptoms remain unchanged, the fault is in the main relief valve or in the valve bank itself. If, however, the defect changes to the other side, the cause is in the pump.2. If one actuator has too little or no pressure while the other actuators in the same valve bank are in order: Check line relief valve (rarely on both sides) of the actuator in question. (See instructions in topic, Line Relief Valve for details.)3. The boom cylinders sink (drift) too rapidly in the control neutral position: Close cutoff valve on the piston crown side of the cylinder (in cab). If the equipment no longer sinks, the fault is in the associated line relief valve. If the equipment continues to sink, check the cylinder seals. Note that a certain amount of leakage in the valve bank is unavoidable. Fig. WH 146 shows the maximum permissible oil leakage including line relief valves and the makeup valve in cm3 as well as the calculated downward travel on the hydraulic cylinder in mm as a function of the boom cylinders pressure for both 50°C and 70°C hydraulic oil temperature.4. The operating motions are too slow, although pump delivery and pressurization are in order: Check pilot control pressure.5. The hydraulic oil temperature is too high: a. Check oil cooler for soiling. Also check air supply below the air shrouding on diesel engine (leaves, foreign objects or the like).b. Check lower intake of Deutz diesel engine for leakage to engine side door. If the blower scoop seal is defective or missing, there will be a direct passage to the hot air of the engine compartment.c. Check oil level in hydraulic oil reservoir. At the same time, make sure that the proper type of oil has been added.d. Observe the operator at work. It may be that he frequently allows travel against the main relief valves.6. Loud noise on one side during hydraulic braking after swinging. Check makeup valve. The noise is almost inevitably on one side, as it is highly unlikely that the same symptom will appear during left and right swing.