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Personal injury can result from hydraulic oil pressure and hot oil. Hydraulic oil pressure can remain in the hydraulic system after the engine has been stopped. Serious injury can be caused if this pressure is not released before any service is done on the hydraulic system. Make sure all of the work tools have been lowered to the ground, and the oil is cool before removing any components or lines. Remove the oil filler cap only when the engine is stopped, and the filler cap is cool enough to touch with your bare hand. |
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| NOTICE |
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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. |
Specifications
| Margin Pressure | |
| The correct margin pressure is 1800 kPa (261 psi) | |
Introduction
This test procedure is intended to measure the margin pressure of the braking and the hydraulic fan pump.
Machines that are equipped with a solenoid for the hydraulic fan cold start bypass refer to System Operation, RENR8471, "Solenoid Valve (Hydraulic Fan) Cold Start Bypass Valve (If Equipped)" for additional information.
Note: Do NOT adjust margin pressure in order to control fan speed unless the calibration for fan speed in Caterpillar Electronic Technician (ET) cannot achieve the minimum desired fan speed or the lowest possible fan speed is within 550 ± 50 rpm.
Required Tools
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| Illustration 1 | g01623868 |
Tooling (B) | |
| Tool | Item | Part Number | Description | Qty |
|---|---|---|---|---|
| B | 198-4240 | Digital Pressure Indicator Gp | ||
| B1 | 198-4234 | Digital Indicator | 1 | |
| B2 | 198-4239 | Pressure Sensor Gp (0 to 41,369 kPa (0 to 6,000 psi)) | 2 | |
| B3 | 198-4236 | Adapter Cable As | 2 | |
| F | 8T-8902 | Tee | 1 | |
| G | 6V-3965 | Fitting | 1 | |
Test Preparation
- Move the machine to a smooth, horizontal location. Move the machine away from other operating machines and away from personnel. Place the transmission direction control switch in the NEUTRAL position. Engage the parking brake. Lower the work tools to the ground. Stop the engine and put chocks in front of the wheels and behind the wheels.
- Remove the pressure from the brake system by pumping the service brake pedal at a rate of one second ON and one second OFF. Continue to pump the brakes until a minimum of 110 applications have been completed. Do not assume that the pressure is removed from the circuit if the brake pedal has no resistance.
- Install Tool (F) between line (1) and fitting (2) . Install Tool (G) into Tool (F) .
 | |
| Illustration 2 | g02145623 |
Brake and hydraulic fan pump (1) Hose (F) Tee (2) Elbow (G) Fitting | |
- Install Tooling (B) onto tooling (G) .
- Remove the cap from test port (3) . Install Tooling (B) onto pressure test port (3) .
 | |
| Illustration 3 | g01373257 |
The manifold is located on the right side of the machine. | |
- Use Cat ET to set the fan speed at 50% of the Maximum rpm.
- Connect Cat ET to the machine.
- Open Cat ET and check for active diagnostic codes. If there is an active diagnostic code, the calibration procedure will be stopped until the condition that caused the diagnostic code is corrected.
- Once any active diagnostic codes are corrected, select the engine Electronic Control Module (ECM) from the available ECM list.
- Then select "Diognostic Tests". A second menu will be displayed. Select "Override Parameters" from the second menu.
Show/hide table
Illustration 4 g01297743
Typical Example
- The "Override Parameters" screen will appear. Select the "Engine Fan Bypass" line and place the number 50 in the"value column". Then select the "Change" button.
Show/hide table
Illustration 5 g01297795
Typical example
Test Procedure
- Start the engine. Operate the machine until the brake system and the fan system are at the normal operating temperature 60° ± 5°C (140° ± 9°F).
Note: Monitor the system temperature throughout the entire test in order to be sure that the temperature stays within the 60° ± 5°C (140° ± 9°F) normal operating temperature range.
- Operate the engine at HIGH IDLE.
- Record the pump discharge pressure from test port (3) . Record the signal pressure from tooling (G) .
The difference between the pressure at test port (3) and the pressure at tooling (G) is margin pressure. The correct margin pressure is 1800 kPa (260 psi).
Adjustment Procedure
- If the margin pressure is incorrect, remove cap (4) and loosen locknut (5) .
 | |
| Illustration 6 | g01295404 |
View of bottom left of engine compartment (4) Cap (5) Locknut | |
- Turn the adjustment screw clockwise in order to increase the margin pressure setting.
Turn the adjustment screw counterclockwise in order to decrease the margin pressure setting.
- Tighten the locknut (5) and reinstall the cap (4) . Perform Step 3 through Step 3 until the margin pressure setting is correct.
- Remove the pressure from the brake system by pumping the service brake pedal at a rate of one second ON and one second OFF. Continue to pump the brakes until a minimum of 110 applications have been completed. Do not assume that the pressure is removed from the circuit if the brake pedal has no resistance.
- Remove all test equipment.