HYDRAULIC OIL TEMPERATURE (TOO HOT)

Relief Valve For Head End Of Tilt Cylinder

TM-5-3805-258-24-1 Loader Scoop Type DED 4x4 Articulated Frame Steer 2 1/2 Cubic Yard Bucket (CCE) Airborne/Airmobile Manual
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TM 5-3805-258-24-1 H Y D R A U L I C S Y S T E M T E S T I N G A N D A D J U S T I N G 4. 5. Disconnect hose assembly (2) and install a 5H4019 Cover in the line. Connect hose assem- bly (2). Look at the test gauge and operate the electric hydraulic pump. The gauge reading must be 26 000 ± 400 kPa (3750 ± 58 psi). 6. If the relief valve needs an adjustment, remove cap (10) from the relief valve. Turn the plunger either clockwise for an increase or counter- clockwise for a decrease in the pressure set- ting of the relief valve. R E L I E F V A L V E F O R H E A D E N D O F T I L T C Y L I N D ER 10. Cap (on relief valve). 7. When the pressure setting is correct, tighten locknut and cap (10) on the relief valve. 8. Remove the test equipment and install the cover over the control valve. The plug and valved nipple can be left on the machine. NOTE: The pressure setting for a new relief valve for the head end of the tilt cyliner is 26 000 ± 400 kPa (3750 ± 58 psi) with an oil flow of 19 ± 2 liter/min 10 ± 1 U.S. gpm). HYDRAULIC OIL TEMPERATURE (TOO HOT) When the temperature of the hydraulic oil gets over 98.9°C (210°F), polyurethane seals in the system start to fail. High oil temperature causes seal failure to become more rapid. There are many reasons why the temperature of the oil will get this hot. 1. Hydraulic pump is badly worn. 2. Heavy hydraulic loads that cause the relief valve to open. 3. The setting on the relief valve is too low. 4. Too many restrictions in the system. 5. Hydraulic oil level in the tank is too low. 6. High pressure oil leak in one or more circuits. 7. Very dirty oil. 8. Air flow through the oil cooler core is too low. 9. Oil flow through the oil cooler is too low. 10. Air in the hydraulic oil. NOTE: If the problem is because of air in the oil, it must be corrected before the system will operate at normal temperatures. There are two things that cause air in the oil (aeration). a. Return oil to the tank goes in above the level of the oil in the tank. b. Air leaks in the oil suction line between the pump and the tank. 4-78

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