Kubota U48-4 Piston Pump Air Bleeding Procedure

This instruction show you guide on how to perform piston pump air bleeding for Kubota U48-4 and U55-4 excavator.

 

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Piston Pump Air Bleeding Procedure
When disassembling hydraulic equipment and replacing hoses,etc., or after changing the hydraulic fluid and using the vacuum pump, before operating the machine, be sure to carry out air bleeding to prevent pump scorching and cavitation.

1.After operating, with the engine stopped, remove the hose at the top of the pump from its clamp.
2.Insert a hexagonal plug, pinch the black plastic lock section, and pull out the hexagonal plug.
3.Drape the hose on the front of the weight, and leave for 30 seconds.
4.Fit a hexagonal plug to the hose, start and idle the engine, and check whether there is any cavitation noise from the pump.
5.Repeat operations in 2. 3. 4 until pump cavitation noise subsides.
6.When cavitation noise subsides, raise the engine speed to 1500 rpm, slowly operated the arm and check whether cavitation noise is emitted. (Make sure there is no relief when operating the arm)
7.If there is no cavitation noise, raise the engine speed to 2000 rpm, slowly operate the arm, and check again for cavitation noise. If cavitation noise is emitted, stop the engine and carry out 2. 3.
8.If there is no cavitation noise in step 7, raise the engine speed to maximum rpm, slowly operate the aim, and check again for cavitation noise. If cavitation noise is emitted, stop the engine and carry out 2. 3. (Make sure there is no relief when operating the arm)
9.If there was no cavitation noise when performing step 8, air bleeding is finished. Clamp the air bleed hose in its original position.

 

(1) Air bleed hose
(2) Hexagonal plug
(3) Lock section

 

More repair case for Kubota,please refer to:Kubota Trouble Repair