Replacement parts for the original Hydro-Vac system are getting harder to find, and what is available is generally of low quality. This converts it, with all brand new parts, to reliable and much more supportable air brake parts. Converting to air-hydraulic makes everything the same as full air-brakes, except that you don't have to change your hydraulic brake axles to do it.
Our Air-Hydraulic brake system uses an air-valve/pedal assembly to apply a remotely mounted air brake booster. It uses air pressure from a belt driven or 12 volt onboard air system to control the air-hydraulic booster, just like the brake system on super sized big rigs and buses, but it pushes a master cylinder rather than the roller cam that mechanically spreads the brake shoes apart on full air brake systems, so it will operate your existing hydraulic brake calipers or drums. It is great for vehicles with a lot of horsepower, a lot of weight, limited firewall clearance, that don't have power steering pressure or enough vacuum to run other brake systems, and/or already have air tanks onboard for operating air-ride suspension or air powered tools.
Most of the system is mounted remotely, usually on the frame or in the trunk. The only thing attached to your brake pedal is the air valve that is about the size of your fist, and you can even remove the stock pedal altogether and go with a pedal that we supply that mounts on the floorboard and puts the valve on the other side of the floorboard. You will have air pressure come in from the tank to the valve, and another air hose that goes from the valve to the booster/master that is on the frame. The booster has two chambers, one does the normal brake application, and the other is the emergency/parking brake. You will have another valve that you can mount on the dash, or hide under the seat or dash, which you can push and pull to manually apply a hydraulic parking brake that locks all four wheels. The hydraulic parking brake feature is much more powerful than the standard cable parking brake, can serve as an anti-theft device if the valve is hidden, and is there to also apply the brakes if you lose air. The system can be built with just the service chamber and no parking brake chamber if it is unneeded or unwanted in your application. If a set of glad hands is also installed, this system will allow your vehicle with hydraulic calipers or drums to pull a trailer that is equipped with air-brakes, or a trailer with hydraulic wheel cylinders that also has one of these Air-Hydraulic systems installed.
It operates off of 120-150 pounds of air pressure, which is much higher than the 15-20 pounds of vacuum that vacuum brake setups use (if the engine is producing enough or any vacuum), and is more serviceable than Hydro-Vac systems that are no longer generally used. The Hydro-Max has a backup motor that assists in stopping if your engine dies, which is a great feature, the Air-Hydraulic will have 10-20 or more stops in reserve in the air tank and the air compressor will continue to produce more if the battery still provides electricity.
Systems can be setup with or without an air compressor and tank, and can easily be designed to replace obsolete systems with just a few measurements - like the master cylinder bore diameter of your current setup. Dual/split systems with multiple boosters and master cylinders that are isolated front and rear are also available and would be used for redundancy/safety or for a "limp home" mode so that one half of the brake system will work if the other fails.