GLASS-FIXED 1459086 - Caterpillar

During diagnosis of the hydraulic system, remember that correct oil temperature, flow and pressure are necessary for correct operation. Pump output (oil flow) is a function of engine speed (rpm). Oil pressure is caused by resistance to the flow of oil.Visual Checks
A visual inspection of the system is the first step when troubleshooting a problem. Make the inspection with the engine off and the attachments lowered to the ground.1. Check the level of the oil in the hydraulic tank. Slowly loosen the hydraulic tank air vent plug and release the pressure before the filler cap is removed.2. Remove the filter element and check it for material that would give an indication of damage to a component.3. Inspect all lines and connections for damage or leaks.4. Inspect control linkage for bent, broken, or damage components.Checks During Operation
The checks during operation can be used to find leakage in the system. They can also be used to find a valve, pump, motor or cylinder that is not working correctly. The speed of rod movement or the torque on a motor can be used to check the condition of the cylinders, motors and pumps.Release Of Pressure In The Hydraulic System
Release the pressure in the attachment hydraulic circuits (boom, stick, and heel) before any hydraulic lines or components are disconnected or removed.1. Fully extend the stick cylinder rod.2. Adjust the position of the heel so that it will be stable on the ground when the boom is lowered.3. Lower the boom until the heel is flat on the ground.4. Shut off the engine and place key in the ON position. Put the hydraulic activation control lever in the UNLOCK position.5. Move the control levers for boom, stick and swing to all full stroke positions. This will release any pressure that might be present in the pilot system.6. Return the key to OFF position.7. Slowly loosen the fill plug on the hydraulic tank and release the pressure.8. Tighten the fill plug on the hydraulic tank.9. The pressure in the hydraulic system has been released and lines and components can be removed.Release Of Air From Main Pumps
When the main pumps have been serviced or the hydraulic oil has been replaced, remove air from the hydraulic system as follows. No attempt should be made to start the engine until the main pumps have been filled with hydraulic oil, or serious damage can be caused to hydraulic components.
Pump Compartment
(1) Air vent plug.1. With the engine stopped, remove air vent plug (1) on the top of the main pump. Leave the plug off for several minutes until the main pumps are filled with hydraulic oil. After the pumps are filled with oil, tighten the vent plug and start the engine. With the engine at low idle, fully raise the boom and hold it in this position.2. Stop the engine and slowly lower the boom until the heel is on the ground. This pressurizes the hydraulic tank.3. Slowly loosen the air vent plug several turns until oil flows out