HEAD 6J1560 - Caterpillar

Hydraulic oil pressure can remain in the hydraulic systems after the engine and pump have been stopped. Serious injury can be caused if this pressure is not released before any service is done on the hydraulic systems. To prevent possible injury, refer to the section, Testing and Adjusting, "Hydraulic System Pressure - Release" before any fitting, hose or component is loosened, tightened, removed or adjusted.When possible, the work tool must always be lowered to the ground before service is started. When it is necessary for the boom to be in the raised position while tests or adjustments are done, be sure that the boom, stick and work tool have correct support.The swing lock must be engaged before service is started.Always move the machine to a location away from the travel of other machines. Be sure that other personnel are not near the machine when the engine is running and tests or adjustments are being made.
Specification
Table 1
Main Pump Cutoff Pressure
Machine Settings Engine Speed
Engine Speed Dial "High Idle"
Item Specification Actual
301.5 / 301.6 301.7 CR / 301.8 / 302 CR
Main pump cut off pressure 21300 1000 kPa (3089 145 psi) 24500 1000 kPa (3553 145 psi) Introduction
Cutoff Pressure is the maximum pressure that can exist in the main hydraulic system before the hydraulic pump destrokes, thus lowering system pressure. A low cutoff pressure setting can decrease performance of the implements. A high cutoff pressure could damage components. Use the following procedures to test or adjust the cutoff pressure.Required Tools
Table 2
Required Tools
Part Number Description Qty
198-4240 Digital Pressure Indicator Gp
198-4234 Digital Indicator 1
198-4238 Pressure Sensor Gp
34450 kPa (5000 psi) 1
198-4236 Adapter Cable As 1 Machine Preparation
Position the machine on level ground.
Stop the engine.
Release the pressure in the hydraulic system. Refer to Testing and Adjusting, "System Pressure-Release".
Illustration 1 g06287501
Main hydraulic pump
(1) Pressure tap (pump cutoff pressure)Note: Pressure tap (1) is used to check cutoff pressure of main hydraulic pump.
Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting, and repair of the product. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids.Refer to Special Publication, NENG2500, "Dealer Service Tool Catalog" for tools and supplies suitable to collect and contain fluids on Cat® products.Dispose of all fluids according to local regulations and mandates.
Attach a 34450 kPa (5000 psi) pressure gauge to pressure tap (1).Test Procedure
Start the engine.
Place the machine controls at the following settings: engine speed dial "High Idle".
Increase the hydraulic oil temperature to 55° 5°C (131° 9°F).
Place the hydraulic activation control lever in the UNLOCKED position.
Move the joystick for the bucket until the bucket is at the full BUCKET OPEN position (full retraction of bucket cylinder). Hold the joystick for the bucket in this position.
Check the pressure reading for the pump cutoff pressure at pressure tap (1).
Return the joystick for the bucket to the NEUTRAL position.
Refer to Table 1for the allowable pressure range. If the