For 1990-2009 cars

The exhaust brake restricts the flow of exhaust gases. The restriction compresses the exhaust gases. The compression of the gases creates a back pressure that slows the vehicle with the engine and the transmission. A small opening in the butterfly valve performs the following functions:

• | Prevents the buildup of excessive exhaust system pressure

• | Protects the engine from damage when the exhaust gas flow level is high

The following actions occur simultaneously during operation:

• | Air at line pressure is directed to the exhaust brake actuator.

• | The fuel supply to the engine returns to an idle condition.

The air pressure in the actuator pushes against the actuator return spring. As a result, the return spring is overcome. This action causes the following results:

• | The push rod extends.

• | The push rod rotates the butterfly valve to the closed position.

Rest condition occurs when the air supply to the actuator is removed. The following actions occur during rest condition:

• | The actuator return spring retracts the push rod.

• | The butterfly valve returns to the open position.

| This position enables unrestricted flow of the exhaust gases.

• | The fuel supply to the engine is restored.