308E CR Mini Hydraulic Excavator Hydraulic System Caterpillar

Note: Before starting main pump flow tests, check the alarm indicators on the operator monitor panel for normal operation. If no faults are present, perform the operational checks. Refer to Testing and Adjusting, "Operational Checks".

Note: If the operational checks (cycle times) indicate that slow speed of an implement is common to the circuits of one pump, the problem is most likely in the hydraulic system. Then perform the pump flow tests. Refer to Testing and Adjusting, "Main Pump (Flow) - Test".

Note: The engine, the fuel, or the working altitude may be the problem if the operational checks indicate that slow speed of an implement is common to both pump circuits.

Note: Perform the following procedures before testing the main pump flow.

• Set the pilot pressure to the specifications in Testing and Adjusting, "Relief Valve (Pilot) - Test and Adjust" for the machine.

• Set the main relief valve to specifications. Refer to Testing and Adjusting, "Relief Valve (Main) - Test and Adjust" for the machine.

Illustration 1	g03002343
Flow meter tool layout (1) 4C-6482 Nipple Assembly (2) 7M-8485 O-Ring Seal (3) 1U-7641 Elbow (4) 7J-9108 O-Ring Seal (5) 8T-0861 Pressure Gauge (6) 6V-3989 Unvalved Nipple (7) 6V-4143 Coupler Assembly (8) 6V-3014 Hose (9) 4C-6481 Coupler Assembly (10) 7M-8485 O-Ring Seal (11) 4C-8767 Coupling (12) 5P-1010 Sleeve (13) Delivery line for main pump (14) 7J-8485 O-Ring Seal (15) 6V-9832 Face Seal Plug (16) 138-7538 Connector (17) Pressure Tap (main pump delivery pressure) (18) 6V-9508 Face Seal Plug (19) 6V-8397 O-Ring Seal (20) Signal Pressure Line for Flow Control (main pump) (21) Elbow (22) 5P-0201 Hose (23) 8C-9026 Adapter (24) 6K-6307 O-Ring Seal (25) 4C-9910 Portable Hydraulic Tester (Flow meter) (26) 4I-6140 Adapter (27) 6V-9853 Fitting (28) 6v-9746 O-Ring Seal (29) 6V-9832 O-Ring Face Cap (32) Main Control Valve (44) 109-7075 Connector (45) 6V-9746 O-Ring Seal (46) 6V-9829 O-Ring Face Cap

Main Pump

Illustration 2	g02849298
Pump compartment (13) Delivery line for main pump (17) Pressure tap (main pump delivery pressure) (20) Signal pressure line for flow control (main pump) (21) Elbow

1. Position the machine on level ground.

2. Stop the engine.

3. Release the pressure in the hydraulic system. Refer to Testing and Adjusting, "System Pressure - Release".

4. Attach 311-1362 Vacuum Cap onto the hydraulic tank. Attach an air supply hose onto the assembly. Apply 276 to 414 kPa (40 to 60 psi). This procedure will pull a vacuum on the hydraulic system.

5. Install the following tools in accordance with the flow meter tool layout. Refer to Illustration 1.

   1. Disconnect delivery line (13) from main pump (32) .

   2. Install seal (14), connector (44), seal (45) and cap (15) in the open end of delivery line (13) .

   3. Assemble and install connector (16), seal (4), elbow (3), seal (2) and nipple assembly (1) to connector (16) at main pump (32) .
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   Illustration 3	g03004816
   Hydraulic valve compartment (29) O-Ring face cap (30) Slow return check valve (31) Crossover tube (32) Main control valve

   4. Disconnect crossover tube assembly (31) from connector (30) and ball valve for tool control. Install o-ring face cap (29) onto ball valve.

   5. Install seal (10) to fitting (26) then install in nipple assembly (1). Install seal (2) to fitting (27). Install the fittings (26), (27) to the slow return check valve (30) along with o-ring (28) .

   6. Connect portable hydraulic tester (25) and the test hoses between nipple assembly (1) at the main pump and nipple assembly (1) at the slow return check valve (30) .

   7. Disconnect signal pressure line (20) from elbow (21) .

   8. Install seal (19) and plug (18) in the open end of signal pressure line (20). Leave elbow (21) open to the atmosphere.

   9. Remove 311-1362 Vacuum Cap and install the filler plug for the hydraulic tank.

6. Connect a 60000 kPa (8700 psi) pressure gauge (5) to pressure tap (17) for main pump delivery pressure.

7. Use 1U-6602 Photo Tach to read the engine speed.

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To prevent personal injury or equipment damage from failure of the hydraulic test equipment or associated circuit components because of blocked pump flow, make sure that the test equipment valves are fully open before starting the engine.

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To prevent personal injury and/or equipment damage from failed lines or components while the hydraulic test equipment is returned to the open flow position, slowly open the hydraulic test equipment valve while monitoring the pump flow. If pump flow does not increase as the valve is opened, shut the engine off and determine what is preventing the pump from upstroking.

8. Start the engine.

9. Place the machine controls at the following settings: Engine speed at high idle, and AEC switch OFF. Refer to Testing and Adjusting, "Engine Performance - Test (Engine Speed)" for engine rpm settings.

10. Increase the hydraulic oil temperature to 55° ± 5°C (131° ± 9°F).

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Illustration 4	g01622422
(25) 4C-9910 Portable Hydraulic tester (Flow meter) (39) Valve

11. Slowly turn valve (39) on portable hydraulic tester (25) clockwise until the pressure gauge reading at pressure tap (17) for main pump delivery pressure is at the first measuring point. Refer to Table 2 for the measuring points.

12. Record the pump flow and the engine speed in Table 2.

13. Repeat Step 11 through Step 12 for all of the measuring points in Table 2.

Note: Specifications for flow rates are based on an engine speed of 2000 rpm. To attain more accurate test results, measured flow should be corrected with the following calculation.

Note: Flow measurements must be done only during pressure rise.