793C Off-Highway Truck Caterpillar

Towing With Inoperable Engine

Usage:

793C 4AR

This machine is equipped with spring-applied parking brakes. These brakes are released with hydraulic pressure. If the engine is inoperable or if the power train is inoperable, the parking brakes are engaged and the machine cannot be moved.

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Personal injury or death could result when towing a disabled machine incorrectly.

Block the machine to prevent movement before releasing the brakes. The machine can roll free if it is not blocked.

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Illustration 1	g00689106

Keep transmission control (1) in the NEUTRAL position. When possible, engage parking brake control (2).
Block the wheels.

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NOTICE

When towing the machine, attach tow line to the front tow hooks or rear tow pin only.
Hook up the towing machine. Refer to this Operation and Maintenance Manual, "Towing the Machine" for guidelines.
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Illustration 2 g00290093

Location of the pressure tap for the parking brake release lines

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Illustration 3 g00640606
Attach a 8T-0857 Pressure Gauge and a line in the pressure tap at one of the junction blocks. The junction blocks are located in the parking brake release lines.
Check the steering of the disabled machine. If the steering needs assistance, use an auxiliary power unit as a separate hydraulic source. Consult your Caterpillar dealer for further information.
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Illustration 4 g00689099

Move the parking brake switch to the OFF position. Turn the engine start switch to ON position (4). Open the guard and move brake release switch (5) to the ON position. Holdthe brake release switch until the pressure that is shown on the pressure gauge stops rising.

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NOTICE

The parking brake must be fully released. Partial brake engagement and brake damage could occur if proper hydraulic pressure is not maintained. Do not allow the parking brake release pressure to drop below 3445 kPa (500 psi) when the towed machine is moving.

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Illustration 5	g00689118

Note: Monitor air pressure gauge (6). The air pressure in the air system must be at 550 kPa (80 psi) in order to tow the machine. If there is not sufficient air pressure in the air system, the air system can be charged with air from another source.

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NOTICE

Do not exceed the air pressure of 830 ± 35 kPa (120 ± 5 psi) or damage can occur to the air system components.

Apply the service brake pedal on the disabled machine in order to check the braking. If the brakes are functioning, release the brakes.
Rotate the steering wheel to each side in order to check the steering.
Remove the blocks from the wheels.
Pull the disabled machine with the towing machine. Watch the pressure gauge that was installed in Step 4. Do not continue to tow the machine if the oil pressure is below 3445 kPa (500 psi).