HOSE AS 2102127 - Caterpillar

Introduction
Leakage from a hydraulic cylinder past the main control valve spool can cause excessive cylinder drift. While a certain amount of leakage can be expected because of the spool to housing bore clearances, too much leakage can cause the cylinder drift to exceed the permissible limit.This test provides a means of checking the leakage rate of the main control valve.Bench test the main control valve for leakage
a. Stop the engine and release the pressure in the hydraulic system. Refer to "Release Of Pressure In The Hydraulic System", Form SENR6187.b. Remove the main control valve from the machine. Refer to Form SENR6189 for additional information.c. Position valve on a test bench which is capable of supplying 5600 kPa (800 psi) to the valve. Place a suitable container beneath the control valve to catch the leakage.d. Connect a supply line to the cylinder port being tested.e. Using 10W oil, at a temperature of 27°C (80°F).f. Apply 5600 kPa (800 psi) oil pressure to the port being tested for one minute. Make certain the control valve spool remains in the NEUTRAL position.g. Measure the amount of leakage from the control valve. Expected Result:* Maximum permissible leakage from the control valve in one minute when tested at 5600 kPa (800 psi) with 10W oil at 27°C (80°F) should be:* Boom rod end port = 24 ml [1.5 cu in (.8 oz)]* Boom head end port = 24 ml [1.5 cu in (.8 oz)]* Bucket rod end port = 11.5 ml [.72 cu in (.38 oz)]* Bucket head end port = 12 ml [.75 cu in (.4 oz)]* Stick rod end port = 24 ml [1.5 cu in (.8 oz)]* Stick head end port = 24 ml [1.5 cu in (.8 oz)]* Swing left and right = 13.5 ml [.85 cu in (.45 oz)] Results:* LEAKAGE OK - STOP.* LEAKAGE NOT OK - Replace the main control valve which contains the valve spool with the excessive leakage. (The spool is not serviced.) STOP.