Saturday, October 21, 2017

Retrofit Hydroboost Brakes

Traditional power brakes have used engine vacuum to reduce the physical effort required to stop a car. Some high performance engines, because of the design of their camshafts, do not produce enough vacuum to used vacuum-powered brake power boosters. One alternative is to add a vacuum pump to the accessories driven by the engine. Another is to use the hydraulic pressure supplied by the power steering pump to power the brake booster. This device is called Hydroboost and it replaces the vacuum-operated brake booster. It provides more than twice the pressure than a vacuum diaphragm booster.

There are commercial kits to use a hydraulic booster, like Vanco. They offer kits to match the car you are modifying. The most complete kits provide the Hydroboost unit, a new master brake cylinder, a power steering pump and the appropriate hoses with fittings and they are priced at around $900. You can see the parts of the kit by visiting this link. A nice step-by-step installation of the Vanco hydraulic booster is available at Stu-Offroad. It is very thorough and has lots of pictures and useful links to related information. Note that the hydraulic unit itself can be "clocked" by 180 degrees in case you need to route the hydraulic lines differently.

Here's the thing, the Hydroboost units themselves are only as far away as your local boneyard and cost $100 to $200. A list of potential donor cars is at and Off-Road Forums. Re-manufactured units are available from eBay from $150 and up, and new units are also available from the local auto parts stores. The most common unit is an A1 Cardone 52-7359. Your car already has a brake master cylinder, so there's no need to  replace that. All that leaves are the hoses and fittings. The size of the fittings will vary depending on the donor vehicle.

Hydratech Braking Systems also provides all-new-component kits where one option is a "full show" finish on the components. They also offer hose fittings and complete hose sets.

Here is a HOWTO page with lots of pictures created by a customer of Hydratech. It is useful for the excellent pictures and a very detailed dialog about the process.

At the Jalopy Journal, there's a discussion about Hydroboost brakes. A fellow who used a unit from a Lincoln Versailles makes the excellent point that if you are using a boneyard unit, get all the hoses associated with it.

BANGshift offers a HOWTO for a Hydroboost upgrade of your truck or muscle car. Many good pictures.

A DIY HOWTO is provided by The Diesel Stop, and addresses modifying mounting holes to fit the device on your vehicle.

Carl Casanova's 1968 Camaro Home Page discusses, among other things, his homemade approach to adding Hydroboost brakes to his Camaro.  He uses a 1999 Mustang unit which differs from GM units in that the attachment bolts are vertical, not horizontal.

A Corvette Forum discussion claims that the units from a 1994-95 Astro van are adapted to GM cars with the least amount of trouble.

The Hollister Road Company offers a thorough HOWTO of how to adapt these units and includes some nice fabrication tips as well as a hand-drawn illustration of how these are plumbed that is more useful than anything else I've seen. They also include more detailed information about hose fittings.

The forum at 67-72 Chevy Trucks also provides a HOWTO of a Hydroboost (from the Hollister Road Company) installation using a unit from a 2001 Chevy Silverado. The unit itself is identified as an A1-Cardone # 52-7359 that comes with a diagram to identify the ports ($95 plus $44 core deposit). This discussion also deals with fabricating a bracket to suspend the brake pedal. What is discussed here and I have not seen discussed elsewhere is the output pushrod, retainer and spring. These pieces connect the Hydroboost unit to your master cylinder, so they are important.

Super Chevy has an article about installing a Hydroboost unit in a '68 Camaro. The pictures are good, but as a HOWTO, not much help. The unit was provided by, I believe, Power Brake Service. They offer quite a variety of power brakes components.

There are, of course, several YouTube HOWTO videos on Hydroboost conversions. YMMV

Car Done provides an installation guide in PDF format, which includes some useful diagrams and a trouble-shooting guide.

GM Fullsize offers a HOWTO using a boneyard-sourced Hydroboost unit and hoses from Autozone. This is probably the most thorough guide to the pats needed and the procedures needed I've seen.

Speaking of AutoZone, they offer a Hydroboost Repair Guide with illustrations, testing and troubleshooting information.

Hot Rod Magazine offers a very brief HOWTO, but the pictures are worth viewing. It seems similar to the Super Chevy offering above as well as this one from Car Craft, Mat 2011 by Douglas Glad, which was the first article to bring it to my attention.

Also of interest are electric-powered brake boosters (not very reliable) and the very intriguing electric power steering units popular on small foreign cars.

While a used Hydroboost may be the way to go as far as price is concerned, there may be issues such as a worn-out or malfunctioning unit which may be problematic to troubleshoot.