User manual BENDIX LQ-3 LQ-4 FRONT AXLE RATIO VALVE

[. . . ] The LQ-4TM valve may be used to operate brake chambers up to Type 24 without relay or QRV. Pressure delivered to the LQ supply port is reduced by 50% as it passes through the valve and out the delivery port. The 50% reduction occurs only when brake application pressure LQ-3TM FRONT AXLE RATIO VALVE EXTERIOR to the supply port of the LQ is between 0 psi and 40 psi. Brake applications between 40 psi and 60 psi to the LQ supply port are reduced by less than 50% and applications above 60 psi are not reduced at all. [. . . ] (*LQ-4TM VALVE OPERATION SAME AS LQ-3TM VALVE. ) 3 supply line. The 50% reduction will occur while supply line pressure is between 0 and 40 psi. COVER (1) 4. When the supply line pressure exceeds 40 psi, but is below 60 psi, observe that the delivery line pressure is no longer one half and that the delivery line pressure is "catching up" to supply pressure. When supply pressure exceeds 60 psi note that the delivery line pressure is approximately equal. O-RING (6) INNER PISTON SPRING (9) OUTER PISTON (4) O-RING (7) Note: The pressures stated here are examples only. Various piece numbers of the LQ valves may have different pressure settings. For information on a specific installation, consult the vehicle handbook. LEAKAGE CHECKS OUTER PISTON SPRING (5) INLET EXHAUST VALVES (10) O-RING (8) INNER PISTON (3) BODY (2) HOLD OFF SPRING (11) Make and hold a service brake application. Apply a soap solution to the exhaust port and around the seam between the cover and the body. Leakage equivalent to a 1" bubble in 5 seconds is permissible. If the LQ valve does not function as described above or leakage is excessive, it is recommended that it be returned to the nearest Bendix authorized outlet for a factory remanufactured valve under the Exchange Plan. If this is not possible, the valve can be repaired with genuine Bendix parts, in which case the following should prove helpful. Note: Maintenance kits for the LQ-3TM and LQ-4TM front axle ratio valves are available from any authorized Bendix outlet. FIGURE 7 - LQ-4TM FRONT AXLE RATIO VALVE PREVENTIVE MAINTENANCE Important: Review the Bendix Warranty Policy before performing any intrusive maintenance procedures. A warranty may be voided if intrusive maintenance is performed during the warranty period. No two vehicles operate under identical conditions, as a result, maintenance intervals may vary. Experience is a valuable guide in determining the best maintenance interval for air brake system components. At a minimum, the valve should be inspected every 6 months or 1500 operating hours, whichever comes first, for proper operation. Should the valve not meet the elements of the operational tests noted in this document, further investigation and service of the valve may be required. REMOVAL Apply the vehicle parking brakes. Identify and disconnect the supply and delivery lines of the LQ valve. Remove the two mounting bolts securing the LQ valve to the vehicle. DISASSEMBLY 1. Prior to removing the four Phillips head screws and their lockwashers which secure the cover to the body, mark the relationship between the cover and the body. Carefully separate the cover (1) (Figure 7) from the body (2) and remove the inner (3) and outer pistons (4). (The cover is under approximately 30 pound load from the outer piston spring. ) 3. Remove the o-ring (6) from the outer piston. [. . . ] Following the vehicle manufacturer's recommended procedures, deactivate the electrical system in a manner that safely removes all electrical power from the vehicle. Never exceed manufacturer's recommended pressures. Never connect or disconnect a hose or line containing pressure; it may whip. Never remove a component or plug unless you are certain all system pressure has been depleted. [. . . ]