BENDIX SD-03-4504 Manuel D’Utilisation

MOUNTING 

SURFACE

DELIVERY 

PORT (2)

SINGLE 

CHECK 

VALVE

INLET 

EXHAUST 

VALVE

CONTROL 

PISTON

CONTROL 

PORT

EXHAUST

INLET 

VALVE 

SPRING

OUTER SPRING

INNER SPRING

DOUBLE CHECK 

VALVE 

(SUPPLY PORT & 

BALANCE PORT)

BALANCE 

PISTON

INLET 

VALVE 

SEAT

The Bendix

®

 R‑7

™

 modulating valve is used in conjunction 

with a dual air brake system and spring brake actuators.  

Typically the R‑7 modulating valve performs four functions:
1.  Limits hold‑off pressure to the spring brake actuators.
2.  Provides a quick release of air pressure from the spring 

cavity of the spring brake actuator allowing a fast 

application of the spring brake actuators. The valve 

delivers air to the park brake quick release valve (or 

relay) and also releases air in the control line to the 

quick release valve (or relay).  

3.  Modulates spring brake actuator application should a 

failure occur in the primary service brake system.

4.  Prevents compounding of service and spring forces.

The valve has one 1/4" control, one 3/8" supply, one 1/4" 

balance, two 3/8" delivery NPTF ports, and an exhaust 

port protected by an exhaust diaphragm.  The valve 

incorporates two 13/32" holes for mounting.

Trucks only: There is an inverted R‑7 valve, which 

appears inverted from the other pictures in this document. 

A standard R‑7 valve and an inverted R‑7 valve are not 

interchangeable. See Figure 2 for a picture of an inverted 

MOUNTING 

HOLE (2)

EXHAUST

CONTROL 

PORT

DELIVERY (2)

SUPPLY PORT

BALANCE PORT

FIGURE 1 ‑ EXTERIOR & SECTIONAL VIEW.            INSET FIGURE 2 - INVERTED VIEW 

MOUNTING 

HOLE (2)

BALANCE

EXHAUST

CONTROL

SUPPLY

Some early versions 

featured an adjusting screw