797F Off-Highway Truck: Relief Valve (Hoist Cylinder Head End)

Table 1
Required Tools
Qty	Part Number	Description
1	131-5051	DataView Tool Gp
1	131-5064	Adapter Cable As
1	213-3276	Pressure Sensor
1	6V-4144	Quick Connect Couplers
1 ⁽¹⁾	2P-8421	O-Ring Adapters
1 ⁽¹⁾	3D-2824	O-Ring Seals
1 ⁽¹⁾	6V-3965	Fitting As
1 ⁽¹⁾	3J-1907	O-Ring Seals

^( 1 )

Required only when using the hoist cylinder buddy dump ports.

Note: Refer to the Hydraulic System Systems Operation/Testing and Adjusting, "Using Caterpillar DataView to Determine Test Data" in order to learn more about connecting Caterpillar DataView (DataView) to the sensors.

Front view of the hoist control valve
(1) Electrical Connection
(2) Electrical Connection
(3) Relief valve for the main supply pressure(4) Relief valve for the head end of the hoist cylinder


Hoist cylinder (5) Rod end port(6) Head end port

Lower the dump body to the DOWN position.

Stop the engine.

Install one 2P-8421 O-Ring Adapter and one 3D-2824 O-Ring Seal to head end port (6). Connect one 6V-3965 Fitting As and one 3J-1907 O-Ring Seal onto the 2P-8421 O-Ring Adapter .Note: Alternate pressure taps can be used. See Illustration 3.


Rear view of the hoist control valve(7) Head end port

Connect the 6V-4144 Quick Connect Coupler to the 213-3276 Pressure Sensor. Connect this assembly to the rod end port of the hoist control valve. Use the 131-5064 Adapter Cable As in order to connect the pressure sensor to one of the analog inputs on the dataview tool group.Note: In place of the datalogger unit a 0 to 40000 kPa (0 to 5800 psi) 198-4240 Digital Pressure Indicator with the proper test hoses can be used.

Set up the datalogger.Note: Be sure to set the timer on the datalogger in order to allow enough time to start the engine and complete the test.

Start the engine.

Operate the dump body repeatedly until the temperature of the hydraulic oil reaches 38 °C (100 °F).

Disconnect electrical connection (1) for the proportional solenoid valve.Note: Electrical connection (1) must be disconnected for this test. When electrical connection (1) is disconnected, oil will flow from only two sections of the gear pump for the hoist and for the brake cooling in order to open head end relief valve (4). The lower flow of oil will allow head end relief valve (4) to be tested. The oil from the other two sections of the gear pump will flow to the brake cooling circuit.


Main relief valve (8) Locknut(9) Setscrew

Loosen locknut (8) in order to increase the pressure setting of the main relief valve (3) .Note: The pressure setting of the main relief valve (3) is lower than the pressure setting of the head end relief valve (4) .

Increase the pressure setting of the main relief valve (3) by turning setscrew (9) clockwise approximately one half of a turn. This one half of a turn should increase the pressure setting above the pressure setting of head end relief valve (4) for the head end of the hoist cylinders. Count the number of turns so that you can return setscrew (9) to the original setting.Note: Do not increase the pressure setting of the main relief valve (3) too much. If the pressure setting of the main relief valve is set too high, damage to the components of the system could occur.

Start the datalogger on dataview tool group.

Operate the engine at LOW IDLE. Raise the empty dump body until the hoist cylinders are fully extended. Continue to hold the hoist control lever in the RAISE position for five seconds.Note: If a gauge is used, check the pressure setting on the pressure gauge.

Lower the dump body to the DOWN position.

Stop the engine.

Stop the datalogger.

Download the file from the datalogger.

View the graph of the data. Observe the pressure of the relief valve for the head end of the hoist cylinder when the engine is at low idle.Note: The pressure setting of the relief valve for the head end of the hoist cylinder is 23800 ± 500 kPa (3450 ± 70 psi) at LOW IDLE.

If the pressure needs to be adjusted, proceed to Step 19. If the pressure does not need to be adjusted, proceed to Step 23.


Hoist cylinder head end relief valve (10) Locknut(11) Setscrew

Loosen locknut (10) .

With a flat head screwdriver, rotate setscrew (11) clockwise by one quarter of a turn in order to increase the pressure. Rotate setscrew (11) counterclockwise by one quarter of a turn in order to decrease the pressure.Note: Each quarter turn of setscrew (11) changes the pressure approximately 1500 kPa (215 psi).

Repeat Step 11 through Step 18 until the pressure setting is correct.

When the pressure setting of relief valve (4) is correct, tighten locknut (10) on relief valve (4) .

Turn setscrew (9) for the main relief valve (3) back to the original setting.

Repeat Step 11 through Step 18 in order to verify that the main relief valve (3) is set to 22400 ± 500 kPa (3250 ± 70 psi) at LOW IDLE.Note: If adjustments are needed rotate setscrew (9) clockwise by one quarter of a turn in order to increase the pressure. Rotate setscrew (9) counterclockwise by one quarter of a turn in order to decrease the pressure.
Note: Each quarter turn of setscrew (9) changes the pressure approximately 1500 kPa (215 psi).

Tighten locknut (8) on main relief valve (3) when the correct pressure is set.

Reconnect electrical connector (1) and disconnect electrical connector (2) .

Repeat Step 11 through Step 18 in order to verify that the main relief valve (3) is set to 22400 ± 500 kPa (3250 ± 70 psi) at LOW IDLE.Note: If adjustments are needed rotate setscrew (9) clockwise by one quarter of a turn in order to increase the pressure. Rotate setscrew (9) counterclockwise by one quarter of a turn in order to decrease the pressure.
Note: Each quarter turn of setscrew (9) changes the pressure approximately 1500 kPa (215 psi).