DUAL BRAKE TREADLE VALVE BENDIX BRAKE VALVE MODEL E7

GROUP 625

INTRODUCTION. OPERATION. ADJUSTMENT. LEAKAGE TEST. OPERATING CHECK. PREVENTIVE MAINTENANCE. BRAKE VALVE REMOVAL. DISASSEMBLY. ASSEMBLY. INSTALLATION.

1 INTRODUCTION

The Bendix E7 Dual Brake Valve (Fig. 1) is a suspended, pedal--operated type brake valve with two seperate supply and delivery circuits for service and emergency braking. This provides the driver with a graduated control for applying and releasing the vehicle brakes. The E7 model valve is rated for 150 PSI. The E7 circuits work as follows: The primary circuit is the portion of the valve between the spring seat which contacts the plunger and the relay piston; the secondary circuit portion is the portion between the relay piston and the exhaust cavity. The primary circuit of the valve is similar in operation to a standard single--circuit air brake valve, and under normal operating conditions the secondary circuit is similar in operation to a relay valve. The primary circuit is part of a removable cage which also houses the relay piston and the cage which can be removed without removing the entire brake valve. Both the primary and secondary circuits use a common exhaust protected by an exhaust check valve. 1/4 Red Pressure Gauge Air Line 1/4 Green Pressure Gauge Air Line Quick Disconnect Valve Body Pedal Travel Adjustment Bolt Brake Switch

Brake Pedal

Figure 1. E7 Model Brake Treadle Valve Assembly

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GROUP OPERATION
2.1 Applying: Normal Operation - No. 1 (Primary) Circuit When the brake treadle is depressed, the plunger exerts force on the spring seat, rubber graduating spring, and No. 1 piston. The No. 1 piston which contains the exhaust valve seat, closes the No. 1 exhaust valve. As the exhaust valve closes, the No. 1 inlet valve is moved off its seat allowing No. 1 air to flow out the No. 1 delivery port. 2.2 Applying: Normal Operation - No. 2 (Secondary) Circuit When the No. 1 inlet valve is moved off its seat, air is permitted to pass through the bleed passage and enters the relay piston cavity. The air pressure moves the relay piston, which contains the exhaust seat and closes the No. 2 exhaust valve. As the No. 2 exhaust valve closes, the No. 2 inlet valve is moved off its seat allowing the No.2 air to flow out the No. 2 delivery port. Because of the small volume of air required to move the relay piston, action of the No.2 circuit portion of the valve is almost simultaneous with the No. 1 circuit portion. 2.3 Applying: Loss of Air in the No. 2 (Secondary) Circuit Should air be lost in the No. 2 circuit, the No. 1 circuit portion will continue to function as described above under Normal Operation: No.1 Circuit Portion. 2.4 Applying: Loss of Air in the No. 1 (Primary) Circuit Should air be lost in the No. 1 circuit, the function will be as follows: As the brake treadle is depressed and no air pressure is present in the No. 1 circuit supply and delivery ports, the No. 1 piston will mechanically move the relay piston allowing the piston to close the No.2 exhaust valve and open the No. 2 inlet valve and allow air to flow out the No. 2 delivery port.

DUAL BRAKE TREADLE VALVE

2.5 Balanced: No. 1 (Primary) Circuit When the No. 1 delivery pressure acting on the piston equals the mechanical force of the brake pedal application, the No. 1 piston will move and the No. 1 inlet valve will close, stopping the further flow of air from the No. 1 supply line through the valve. The exhaust valve remains closed preventing any escape of air through the exhaust port. 2.6 Balanced: No. 2 (Secondary) Circuit When the air pressure on the No.2 side of the relay piston approaches that being delivered on the No. 1 side of the relay piston, the relay piston moves closing the No. 2 inlet valve and stopping further flow of air through the valve. The exhaust remains closed as the No. 2 delivery pressure balances the No. 1 delivery pressure. When applications in the adjusting range are made, a balanced position in the No.1 portion is reached as the air pressure on the delivery side of the No. 1 piston equals the the effort exerted by the drivers foot on the treadle. A balanced position in the No.2 portion is reached when air pressure on the No. 2 side of the relay piston closely approaches the air pressure on the No. 1 side of the relay piston. When the brake treadle is fully depressed, both the No. 1 and No.2 inlet valves remain open and full reservoir pressure is delivered to the actuators. 2.7 Releasing: No. 1 (Primary) Circuit With the brake treadle released, mechanical force is removed from the spring seat, rubber graduating spring, and No. 1 piston. Air pressure and spring load moves the No. 1 piston, opening the No. 1 exhaust valve, allowing air pressure in the No. 1 delivery line to exhaust out the exhaust port. 2.8 Releasing: No. 2 (Secondary) Circuit With the brake treadle released, air is exhausted from the No. 1 circuit side of the relay piston. Air pressure and spring load moves the No. 1 piston, opening the No. 2 exhaust valve, allowing air pressure in the No. 2 delivery line to exhaust out the exhaust port.

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DUAL BRAKE TREADLE VALVE 3 ADJUSTMENT
The brake pedal must be adjusted to maintain 7 inches of total pedal travel (Fig. 2). If the amount of pedal travel from the fully returned to the fully applied position is incorrect, loosen the locknut at the pedal stop button and thread the stop button in or out to obtain the correct amount of travel. Retighten the locknut when the correct travel dimension has been reached. When correctly adjusted, the roller and plunger should make contact in the fully released position. The roller should be able to be turned freely by your thumb while still making contact with the plunger. If pedal travel in excess of 7 inches is present and cannot be adjusted out, or the pedal slowly sinks and will not hold at a fully depressed position, an air leak or other malfunction in the valve may be present. Perform a leak test to determine if the valve is not holding correct pressure. A defective or suspect brake treadle valve must be replaced immediately.

GROUP 625 WARNING

A change in vehicle braking characteristics or a low pressure warning may indicate a malfunction in one or the other brake circuit. Although the vehicle air brake system may continue to function, the vehicle should not be operated until the necessary repairs have been made and both braking circuits, including the pneumatic and mechanical devices are operating normally. Always check the vehicle brakes after performing brake work and before returning the vehicle to service. If there is any question as to the correct operation of the treadle valve assembly, it should be replaced immediately. Failure to replace a suspect treadle valve assembly could result in equipment damage, serious injury to personnel or death.

Locknut

Stop Button Plunger Roller Fulcrum Pin

7 Total Travel

Figure 2. E7 Brake Pedal Adjustment

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GROUP LEAKAGE TEST
Apply the brake pedal and hold a high pressure (at least 80 PSI). Coat the exhaust port, the valve body and the plunger with a soap and water solution. Leakage permitted is a one inch bubble in 3 seconds. If greater air loss is evident, replace the brake treadle valve.
DUAL BRAKE TREADLE VALVE 6 PREVENTIVE MAINTENANCE
Every 900 operating hours, 3 months or 25,000 miles clean any accumulated dirt, gravel or foreign material away from the treadle, plunger boot, mounting plate and all switches and fittings. Lubricate the treadle roller, roller pin, fulcrum pin and plunger using a barium based lubricant. Apply a thin layer of Barium grease (Bendix part 246671) between the plunger and mounting plate, DO NOT OVER LUBRICATE! Check the rubber plunger boot for cracks, holes or deterioration and replace if necessary. Check the mounting plate hardware and the valve body mounting hardware for integrity and proper torque. Clean the exhaust check valve metal parts with a non-flammable solvent after disassembly and removing diaphragm. Every 7,200 operating hours, 200,000 miles or two years it is recommended that the brake treadle valve assembly be disassembled and checked for worn or damaged parts. Clean and inspect all parts and rebuild or replace the treadle valve depending on condition.

5 OPERATING CHECK

Check the delivery pressure of both primary and secondary circuits using test gauges know to be accurate. Depress the pedal to several positions between the fully released and fully applied positions, and check the delivered pressure on the test gauges to see that it varies proportionately with the movement of the brake pedal. Apply the treadle valve and then release the pedal completely, the reading on the test gauge should fall off to zero promptly when the application is released. Note that primary circuit delivery pressure will be 2 PSI greater than the secondary delivery pressure with primary and secondary circuit supply reservoirs at the same pressure. This is normal.

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DUAL BRAKE TREADLE VALVE 7 BRAKE VALVE REMOVAL
(1) (2) (3) Chock the vehicle wheels and drain all air system reservoirs completely. Mark all air lines and electrical connections at the brake valve. Disconnect the brake switch at the quick disconnect (refer to Fig.1). (4)
Disconnect the 1/4 red and 1/4 green pressure gauge air lines on the right side of the valve body (refer to Fig. 1). Disconnect the electrical leads at the pressure switches and stop light switches on the left side of the valve (refer to Fig. 3). Disconnect the red 3/8 front delivery SR1 air line at the fitting on the left side of the valve (refer to Fig. 3).
Stop Light Switch Red SR1 Air Line
Stop Light Switch Pressure Switches
Figure 3. E7 Brake Valve Removal

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(7) Tag and remove the red 3/8 and 1/2 air lines at the double fitting on the rear of the valve body (refer to Fig. 4). Mounting Bolts Double Fitting 8.2 5/8 Red Air Line 3/8 Red Air Line 1/2 Red Air Line 1/2 Green Air Line 5/8 Green Air Line Mounting Bolt (2) 8.1 (2)
Fashion a hook from a piece of wire and insert hook through inlet--exhaust valve of upper static piston assembly. Pull firmly and remove upper static piston assembly. Remove o--rings (2) and (3). Remove retainer (17), and secondary inlet exhaust assembly (1). Apply firm pressure on spring seat (19), which will compress piston return spring. Locking groove in piston is now accessible through rectangular opening in lower static piston body. Insert wire or screwdriver into locking groove, thus holding static piston spring in compressed position. Insert blade of screwdriver through relay piston exhaust passage into slot of stem, and remove lock nut (14). Take care not to nick or scratch the exhaust seat of the relay piston while removing lock nut. Remove spring seat (15), stem spring (23), spring seat nut (16), rubber spring seat (19) and rubber spring (10). The relay piston, relay spring (5) and stem bolt can now be removed. Removal of screwdriver or wire from locking groove will permit spring load to push the primary circuit piston from the lower static piston. Note: Care should be used when removing tool from locking ring because of spring load. Remove o--rings (6 & 7) from relay piston and o--ring (9) from primary circuit piston. Remove o--rings (two #11 & one #12) from lower static piston. Remove large retaining ring (20) from lower static piston, and remove primary circuit inlet/exhaust valve assembly (4).

Upper Static Piston Assembly (1) (2)
Lower Static Piston Assembly (1)
(3) Figure 4. E7 Air Line Removal (8) Tag and remove the 5/8 red air line from the angle fitting on the rear of the valve body (refer to Fig. 4). Tag and remove the 1/2 and 5/8 green air lines from the bottom fittings on the rear of the valve body (refer to Fig. 4). (6) (7) (8) (4) (5)
(10) Remove the four bolts and locknuts holding the valve body mounting plate to the firewall (refer to Fig. 4). (11) Withdraw the valve body and mounting plate assembly from the firewall by pulling it out from inside the cab. (12) If the treadle valve is being replaced, remove the air line fittings and unbolt the valve body from the mounting plate.

8 DISASSEMBLY

Refer to Figure 5 for the following procedure: (1) Remove retainer (18). Remove the lower static piston assembly.
8.3 Exhaust Check Valve If your unit is equipped with an air exhaust check valve (components 13, 21 & 22) as shown in Figure 5, remove screw (21), and washer (22) and then discard diaphragm (13). Replace (21) and (22) using new diaphragm (13).

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Figure 5. E7 Dual Brake Valve Cutaway

9 ASSEMBLY NOTE

Before assembly, all o--rings, bores and mating surfaces must be lubricated with silicone lubricant 291126 (Dow Corning 55--M). DO NOT LUBRICATE rubber spring. Refer to Figure 5 for the following procedure: (1) Install secondary circuit inlet--exhaust assembly (1) in upper static piston, making certain retaining ring (17) is engaged in groove of upper static piston bore. Install o--rings (2 & 3) on upper static piston and install in valve body. Install primary circuit inlet--exhaust assembly in lower static piston making certain retaining ring (20) is engaged in groove of lower static piston bore. Install three o--rings (two #11, and one #12) in grooves of lower static piston assembly.

(5) (6)

Install o--rings (6) and (7) on relay piston and o--ring (9) on primary circuit piston. Carefully clamp primary circuit piston in a soft--jawed vise taking care not to damage the exhaust seat or the outside diameter. Assemble the rubber spring, (10) over the center stem of the center of the piston, then the spring seat (19) and the spring seat nut (16). Tighten the spring seat nut until the end of the piston stem and the spring seat nut are flush. Insert relay piston spring (5) and relay piston in top end of lower static piston, and primary circuit piston spring (8) and primary circuit piston assembly in the bottom of lower static piston. Install stem bolt through bore of relay piston, invert entire lower static piston assembly and position over a screwdriver mounted in a vise. Engage screwdriver or wire in locking groove and release pressure on piston. Depress primary circuit piston assembly against spring until locking groove is accessible through rectangular hole in side of

(2) (3)

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lower static piston. Engage a screwdriver or wire in locking groove and release pressure on piston. (10) Install stem spring (23), spring seat (15) and stem nut (14). Torque to 20--30 inch lbs. (11) Install the lower static piston assembly in valve body. Install retainer (18) making certain locking tabs engage boss on valve body. (5) (6)
Install the 5/8 red air line on the angle fitting on the rear of the valve body (refer to Fig. 4). Install the red 3/8 and 1/2 air lines at the double fitting on the rear of the valve body (refer to Figure 4). Connect the red 3/8 SR1 air line to the fitting on the left side of the valve body (refer to Fig. 3). Connect the electrical leads to the stop light switches and pressure switches on the left side of the valve body (refer to Fig. 3). Connect the 1/4 red and green pressure gauge air lines to the fittings on the right side of the valve body (refer to Fig. 1).

10 INSTALLATION

(1) Install the new brake treadle valve assembly to the mounting plate.
Use 567 on all NPT threads when installing fittings, switches and connectors into the valve body, or making connection to fittings. (2) (3) Install all air line and switch fittings to the valve body (refer to Figures 1, 3 and 4). Insert the treadle valve assembly into the fire wall and secure with four bolts and nuts (refer to Fig. 4). Install the 1/2 and 5/8 green air lines to the bottom fittings on the rear of the valve body (refer to Fig. 4). LoctiteTM
(10) Install the brake switch in the fitting on the right side of the valve body. Reconnect the switch lead at the quick disconnect (refer to Figure 1). (11) Build up air pressure in the system to the normal maximum value. Coat all valve fittings and air line connections with a soap and water solution. Depress and hold the brake pedal. If any air leakage is evident, reinstall connections or replace components. (12) Remove wheel chocks from the truck and test the brake system for correct operation.

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