is integral with the Hydrovac unit. This hydraulic cylinder, in turn, actuates the vehicle brake cylinders through hydraulic connecting lines.

When the driver takes his foot off the brake pedal, the pressure in the hydraulic lines drop, and as pressure on the hydraulic plunger in the control valve is relieved, the diaphragm return spring in the control valve then returns the diaphragm to its released position, thus closing the atmospheric valve and opening the vacuum valve. The power cylinder chambers are again all connected to vacuum so the power cylinder return spring now moves the cylinder pistons and push rod away from the hydraulic slave cylinder, releasing the pressure on its check valve and piston. The wheel cylinder pressure is then relieved and the entire hydraulic system returns to its normal line pressure.

Removal of Hydrovac from Vehicle

1.Disconnect the hydraulic brake lines at the Hydrovac unit which lead to the Hydraulic Master Cylinder and the Wheel Cylinders.
2. Disconnect air cleaner hose connection.
3. Remove the bolts which retain the Hydrovac unit in the mounting brackets, and move the unit sufficiently to use a screw driver on the hose clamp at the vacuum line connection.
4. Remove the hose connection to the vacuum line and remove unit.

NOTE: Do not attempt to service the unit without first obtaining the proper RK Repair Kit which contains all the necessary parts that should be used when reassembling. If RK Kits are not available, make sure that all parts which make up the proper kit are available. See page 25 for component parts, First Series Hydrovac RK Kits, and pages 51 through 54 for component parts for Second Series Hydrovac RK Kits.

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