Parking Brake Release Motor: Description and Operation

Fig. 8 Connections for automatic parking brake release. Typical:

The vacuum power unit will release the parking brakes automatically when the shift lever is moved into any drive position with the engine running. The brakes will not release automatically, however, when the shift lever is in neutral or park position with the engine running, or in any position with the engine off. The power unit piston rod is attached to the release lever. Since the release lever pivots against the pawl, a slight movement of the release lever will disengage the pawl from the ratchet, allowing the brakes to release. The release lever pivots on a rivet pin in the pedal mount.As shown in Fig. 8, hoses connect the power unit and the engine manifold to a vacuum release valve in the transmission neutral safety switch. Moving the transmission selector lever into any drive position with the engine running will open the release valve to connect engine manifold vacuum to one side of the actuating piston in the power unit. The pressure differential thus created will cause the piston and link to pull the release lever.