SECTION-KT- 1049414 - Caterpillar

Machine Preparation
Position the machine on level ground and stop the engine.
Release the pressure in the hydraulic system. Refer to Operation and Maintenance Manual, "System Pressure Release".
Illustration 3 g06180018
Pressure tap for pump 1
Attach a 41,368 kPa (6,000 psi) pressure sensor to the pressure tap for pump 1 .Test Procedure
Standard
Start the engine.
Place the hydraulic activation control lever in the UNLOCKED position.
Place the machine controls at the following settings: engine speed dial "7" and AEC switch OFF. Refer to Testing and Adjusting, "Engine Performance - Test (Engine Speed)" for engine rpm settings.
Increase the hydraulic oil temperature to 55° 5°C (131° 9°F).
Move the joystick for the bucket until the bucket is at the full BUCKET CLOSE position (full extension of bucket cylinder).
Check the pressure reading for the main relief valve pressure setting. Refer to Table 1.
Return the joystick for the bucket to the NEUTRAL position.Heavy Lift (If Equipped)
Note: Machines that are equipped with heavy lift have a high-pressure setting and a low pressure setting for the main relief valve.
Start the engine.
Place the hydraulic activation lever to the UNLOCK position.
Place the machine controls at the following settings: engine speed dial "7" and AEC switch OFF. Refer to Testing and Adjusting, "Engine Performance - Test (Engine Speed)" for engine rpm settings.
Increase the hydraulic oil temperature to 55° 5°C (131° 9°F).
Set the heavy lift to the OFF position.
Move the joystick for the bucket until the bucket is at the full BUCKET CLOSE position (full extension of bucket cylinder).
Check the pressure reading for the main relief valve pressure setting. Refer to Table 1.
Return the joystick for the bucket to the NEUTRAL position.
Set heavy lift to the ON position.
Move the joystick for the boom until the boom is at the full BOOM RAISE position (full extension of boom cylinders).
Check the pressure reading for the setting for heavy lift of the main relief valve. Refer to Table 1.
Return the joystick for the boom to the NEUTRAL position.Adjustment Procedure
Standard
Remove the access plate above the main control valve in order to locate the main relief valve.
Illustration 4 g06195051
Main relief valve
(A) Adjustment screw
(L) Locknut
Loosen locknut (L).
Move the joystick for the bucket until the bucket is at the full BUCKET CLOSE position (full extension of the bucket cylinder).
Check the pressure reading for the main relief valve pressure setting. Refer to Table 1.
Return the joystick for the bucket to the NEUTRAL position.
Adjust the pressure setting for the main relief valve to the specification. Turn adjustment screw (A) clockwise in order to increase the pressure. Turn adjustment screw (A) counterclockwise in order to decrease the pressure.Note: Always make final pressure adjustments on pressure rise.
Tighten locknut (L). Do not allow adjustment screw (A) to move.Heavy Lift (If Equipped)
Illustration 5 g06195071
Main relief valve (heavy lift)
(LH) Locknut for heavy lift
(AH) Adjustment screw for heavy lift
(LM) Locknut for main relief
(AM) Adjustment screw for main relief
Illustration 6 g02103561When the main relief pressure setting is adjusted, the pressure setting for heavy lift is not affected. When adjustment screw (AM) is turned counterclockwise in order to decrease the main relief setting,