Usage:
426C (1CR, 1MR) 436C (1FR, 1PR) 438C (1TR, 2DR) Backhoe Loaders
- SUPPLEMENT: SEPTEMBER 22, 1997
Service Magazine; August 18, 1997; Page 5; "Four Wheel Drive All-Wheel-Steer Dead Engine Brake Inspection."
Disregard this article. See the article with the title"Four Wheel Drive All-Wheel-Steer Brakes", in the September 22, 1997 Service Magazine SEPD0383.
--------------- END SUPPLEMENT ---------------
The C-Series All-Wheel-Steer models use a different brake actuation system than the C-Series Two-Wheel-Steer model. The Two-Wheel-Steer models use a self contained brake system which is composed of a master brake cylinder/valve, reservoir, and associated lines connected directly to the rear axle brakes.
The All-Wheel-Steer models employ a limited slip axle which uses a hydraulic assisted brake system controlled by a single pedal. The All-Wheel-Steer machines derive brake actuation oil from the steering circuit of the machine's hydraulic system. The brake system is composed of 136-5942 Brake Control Valve Group (1) (Illustration 1), 148-9000 Valve Assembly and associated lines that connect the brake system to hydraulic system and the All-Wheel-Steer Brakes.
Illustration 1. 136-5942 Brake Control Valve Group (1).
Illustration 2. Location of 148-9000 Valve Assembly (2).
Illustration 3. Hydraulic Schematic.
The 136-5942 Hydraulic Brake Control valve provides a signal to the hydraulic pump and controls flow and pressure to the rear axle brakes.
The 148-9000 Brake Sequence Valve prevents interaction between the brakes and other portions of the hydraulic system. Maximum Brake System pressure is controlled by the relief valve in the Steering Priority Valve Pressures can be measured at the pressure taps provided on the pump. See Chart 2 for typical pressures expected when the brakes are operating properly. These pressures are measured when the engine is running and the brakes are fully applied.
Procedure to Dead Engine Brake Inspection
1. Back the machine up an incline which is 20% or less.
2. Set parking brake to hold the machine.
3. Shut off engine.
4. Using high force, depress brake pedal.
5. Release parking brake.
6. Machine movement should be controllable by increasing pedal force.
7. If machine movement can not be controlled, the brake control valve is not functioning correctly and should be replaced.