VALVE GP-CONTROL 3773676 - Caterpillar

Air must not be in the oil for the brake hydraulic system. Air in the system can prevent complete brake application and it is possible that the wheels on the vehicle can not be stopped.
CHECK OF SMALL PISTON MOVEMENTCheck Front Wheel Brake Linings For Wear (Expander Tube-Type)
FRONT BRAKE CROSS SECTION - EXPANDER TUBE-TYPEThe brake lining and shoe assemblies are located between the brake drum and retracting springs.Before removing the wheel and tire, check the linings for wear. The linings must be replaced when there is no curve in the retracting spring. The front brakes must be activated to check lining wear.Maximum permissible lining wear is indicated when edge (1) of the brake shoe contacts face (2) of the retracting spring when the brakes are applied. However, linings should be replaced before this point is reached.
LOCATIONS TO CHECK FOR LINING WEAR (Each Wheel Has 12 Locations)
CHECKING LINING WEAR (View Through Retracting Spring Slot)
1. Edge of shield (part of expander tube). 2. Inner face of retracting spring.
Before removing the wheel and tire, remove the air pressure from the air tanks. Do not activate the brake after a wheel and drum have been removed. If all of the air has not been removed and the brakes are applied, it is possible for the retracting springs and/or lining and shoe assemblies to move out with sufficient force to cause personal injury.
Reline in full sets of linings only, and install each lining and shoe assembly with a new retracting spring. In most cases, it is advisable to replace the expander tube assembly at the same time.Check Front Wheel Brake Linings For Wear (Caliper Disc)
Check Linings
FRONT BRAKE CROSS-SECTION (CALIPER DISC)
1. Disc. 2. Lining thickness. 3. Carrier-lining assemblies. 4. Calipers. 5. Disc thickness.Carrier-lining (3) is part of the stationary brake caliper (4). There are two carrier-linings for each caliper. Rotation disc (1) rotates between the two carrier linings causing lining wear. The linings can be visually checked for thickness (2). The carrier-lining assembly must be replaced when the minimum thickness is .125 in. (3.20 mm).Check Disc
Disc (1) should be checked for damage or wear. Replacement should be made when the minimum thickness (5) is .625 in. (15.87 mm).Check Pin Clearance
Carrier and lining assemblies (3) are held in position by pins (6). Each of the pins (6) are locked in position with a bolt (7).Clearance between pins (6) and disc (1) should be .060 to .125 in. (1.52 to 3.20 mm). When the proper clearance has been made, tighten bolt (7) to torque of 38 to 42 lb. ft. (51 to 56 N m). Make sure bolt (7) fully engages groove in pin (6) before bolt (7) is tightened.
PIN TO DISC CLEARANCE
1. Disc. 6. Pins. 7. Bolt.Oil Leakage In Retraction Circuit For Emergency Parking Brake
An internal oil leak in the retraction circuit for the emergency parking brake will cause the transmission pump outlet pressure to decrease. A decrease in pressure will not let the transmission clutches engage correctly.Leakage in the retraction circuit can also cause too