What is a hydraulic brake booster?


A hydraulic brake booster replaces your vacuum booster, is powered by the pressure from the power steering pump and it results in ~2-3x the braking pressure for the same amount of pedal pressure as vacuum operated brakes. Pressure using a one ton Hydraulic brake booster can reach 2,400psi at idle to 2,600psi running. It runs off of your power steering pump.


The majority of the units I sell are bolt in, using the existing firewall bolt pattern where possible. In some situations, depending on the year/make of your vehicle, you will be able keep your master cylinder and you don't have to bleed your brakes.


Going the cheap route on hoses will cost you ~$50 at Autozone. Both hoses will need to have the ends at the pump and box first bent to match. If you have flared fittings on your pump and box you need to cut off and remove the end at the box and pump along with the metric nut, next you would install the respective nut from your old brake line (smaller at the pump, larger at the box) and then re-flare the end. NAPA would charge about $10 to do the flaring if you don't have the tools. You will also need to buy six 3/8" hose clamps for the return line and Howe Performance recommends using GM Goodwrench PN: 89020661 for power steering fluid. I recommend flushing the power steering system and making sure that all works again correctly prior to installing the hydraulic brake booster and bleeding it, that helps to isolate any trouble and gives you all fresh fluid. You can source your own brass 3/8 barbed hose fitting for the return line at Plumbing Supply or your local Autozone may have them in the fuel line section of the help parts.


Bleed your brake system if you've replaced the master cylinder, starting with bench bleeding the master cylinder, and do this with the engine off. I would say 98% of the problems folk have installing HB result from a poor MC bleed and you can work at it a good long time but the slightest remaining bubble will foil your efforts. The quick way to do it right the first time is to pick up a syringe bleeder for about $10 and Cardone makes them.


Finally, bleed the hydraulic brake booster as you would just a power steering system. Disable the ignition at first until the pump quits taking on more fluid so you prevent cavitation which can lead to immediate pump wear and failure. Don’t be alarmed if your pedal pulses or stays at the floor initially. Under no circumstances should you attempt to pull the pedal up as you can destroy your internal components. Also, never attempt the bleeding process with the MC removed as you can over extend the piston by pushing on the brake pedal which may lead to a ruined piston and/or seal.


Another way to destroy your hydraulic brake booster on installation is to mismatch an MC with a deep indent for the booster plunger rod with HB that has a shorter rod in it. Most hydraulic brake boosters designed for GM vehicles are set up for a shallow dimple in the MC piston. If you use an MC with a deeper indent and then stomp on the brakes because they don’t seem to bleed well… what will result is that you over extend the piston in the HB which can tear the seal and scar the piston as it jams into the casting material. Just a heads up folk;)


Now, for those of you who wish to install a filter or cooler, those should go in the return line between the steering box/rack and the Tee fitting if one is used. If installed above the Tee it will create back pressure into the HB and result in screwy brake response. Coolers should have a 3/8” ID and be no more than two pass. Filters should be designed for PS systems and Cardone sells a handy, serviceable one (part # 20-0038F). If you have crap in your system and it floats into the HB it can result in intermittent brake lockup and over heating of brake components. Use the right fluid, keep it clean and cool for best service life of your HB.


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Disclaimer: Hydro-Boost is a registered ® trademark of the Robert Bosch Corporation. All products herein are modifications and not directly or indirectly affiliated with the Robert Bosch Corporation unless noted. Custom Power Brake (aka Sterlingworth16) is not affiliated with Bosch. All products herein are designed for off road use only and are not DOT certified. The process to meet DOT certification is extremely lengthy. Any purchase of product and/or use of tech related to these products constitute the understanding that brake line pressure will be dramatically increased and the acceptance of liability or risk related to use.


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