631K and 637K Wheel Tractor-Scraper Systems Parking Brake

NOTICE

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.

Specification

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Table 1
Parking Brake Pressure - Test
Date	Equipment ID Code
Description	Specification	Actual
Parking Brake with Engine Off Switch ON	Less than 500 kPa (72 psi)
Parking Brake with Engine Running and Switch OFF	4000 ± 172 kPa (580 ± 25 psi)

This procedure checks the parking brake pressure at the front wheels.

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Table 2
Tool	Item	Part Number	Description	Qty
B		198-4240	Digital Pressure Indicator Gp
	B1	198-4234	Digital Indicator	1
	B2	251-9600	Pressure Sensor Gp (0 to 68,900 kPa (0 to 10,000 psi))	2
	B3	198-4236	Adapter Cable As	2

Warm the hydraulic oil up to 65° ± 5°C (149° ± 9°F).
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 bowl to the ground and lower the apron onto the bowl. Stop the engine and put chocks in front of the wheels and behind the wheels.
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Illustration 2 g03715898

View of the portion of the belly pan that has the access port.
Remove the crank case guard. For information regarding the removal of the crankcase guards refer to the Disassembly and Assembly, "Crankcase Guard - Remove and Install - Tractor" for your machine.
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Illustration 3 g06218401

The arrow shows the location of the park brake control group.
The area that is involved in this procedure has been exposed.
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Illustration 4 g03715911

Dust cover and test port.
Remove the dust cover and connect (B) to test port (1) in order to check the parking brakes.

Start the engine and run the engine until cut-out pressure is reached. Move the parking brake control switch to the OFF position.
With the engine running at low idle place the parking brake switch to the ON position. The parking brake pressure should be less than 500 kPa (72 psi).
With the engine running at low idle shift the parking brake switch to the OFF position. The parking brake pressure shall be 4000 ± 172 kPa (580 ± 25 psi). Refer to the Adjust Procedure of this article if the pressure reading is incorrect.

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Illustration 5	g06218404
Some hoses are removed for clarity. (3) Stem (4) Lock nut

Apply the parking brake and shut off the engine.
Hold the stem on pressure reducing valve (3) and loosen locknut (4).
Then turn the adjustment stem using a maximum of 1/4 turn intervals.
Hold the stem on pressure reducing valve (3) and tighten lock nut (4).
Start the engine. With the engine running at low idle shift the parking brake switch to the OFF position. The parking brake pressure shall be 4000 ± 172 kPa (580 ± 25 psi). Perform this Adjust Procedure until the setting is correct.
Remove the test equipment and reinstall the crankcase guards. Refer to the Disassembly and Assembly, "Crankcase Guard - Remove and Install - Tractor" for your machine.

Check the accumulator pre-charges by referring to the Testing and Adjusting, "Brake Accumulator (Service) - Test and Charge" in this book. The story provides information regarding the charging values based on temperature.
Purge the brakes thoroughly by referring to the Testing and Adjusting, "Parking Brake Purge Procedure" in this book. This story provides information regarding the purge procedure for your machine.
Check the accumulator pressures at the test ports on the fan and brake block. Refer to Testing and Adjusting, "Brake Accumulator Charging Valve - Test"in this book. This story provides information regarding the Brake Accumulator Charging Valve for your machine.