BRACKET 5075661 - Caterpillar

Master Cylinder - Hydrostatic Brake System
Location of Master CylinderThe master cylinder is located under the dashpanel, which can be tilted for service access.The master cylinder has two stages of operation during a brake application.In the first stage, the cylinder delivers a high volume of oil which takes up the running clearances in the brake packs. In the second stage a smaller volume of oil is delivered at a higher pressure to generate the necessary braking force between the brake pack plates.
Master Cylinder
1. Relief Valve 2. Passage 3. Hole 4. Holes 5. Port to Brake Lines 6. Hole 7. Seal 8. Piston 9. Chamber 10. Cup Seal 11. Chamber 12. Spring 13. Piston 14. Spring 15. Seal 16. Holes 17. Port to Inching Valve (if equipped).When the brake pedal is pressed, pistons (13) and (8) move to the right. Brake oil in chamber (9) is pushed through hole (6) and port (5) into the brake lines. The brake pack pistons move against the brake packs and the running clearance between the plates is taken up. This creates an increase in the brake oil pressure which acts against relief valve (1) through hole (3) and passage (2).When the oil pressure reaches the relief valve setting, oil is metered past the relief valve and piston (13) continues to move to the right.When piston (8) reaches seal (7), hole (6) is closed off from chamber (9). Piston (13) continues moving to the right and oil in chamber (11) is pushed out through the center of piston (8) and into the brake lines, generating a higher pressure against the brake pack pistons due to the smaller diameter of piston (8).When the brake pedal is released, return spring (12) moves piston (13) to the left. Oil is drawn into chamber (9) through hole (6) from the brake lines. Oil is also drawn into chamber (9) from the reservoir through holes (16) and past seal (15). Return spring (14) moves piston (8) to the right and oil is drawn into chamber (11) through holes (4) in the piston and around the outside of cup seal (10).On early machines the reservoir is topped up through port (17) with oil from the return line between the inching valve and the torque converter circuit. Later machines are equipped with a master cylinder reservoir, located under the right side of the dashpanel and connected to port (17) by a hose. The early machines referred to above all have an inching valve. Some later machines also have an inching valve. The change to a master cylinder reservoir did not coincide with removal of the inching valve. The inching valve was removed later.Service Brake Valve - Power Brake System
Location of Service Brake ValveThe service brake valve is located under the operators station floorplate and is attached to the service brake pedal.
Service Brake Valve
1. Spool Return Spring 2. Inlet Port 3. Tank Port 4. Spool 5. Control Spring 6. Housing 7. Operating Piston 8. Stop Light Switch Port 9. Brake Port 10.