1983 Porsche 911 SC Targa

Monday, June 17, 2013

Brake Booster Pump Installation

The first EV component I purchased was a vacuum brake pump kit (see Brake Kit).  For a year and a half that kit has been sitting in a large, but as of late, dwindling stack of parts awaiting installation. After driving around for a couple weeks with no brake booster assist (essentially manual brakes), I decided to install the brake pump.  The brakes stopped the car just fine, as I have been limiting my top speed to 45 MPH until the motor brushes are seated. But, if ever a situation demanding a quick stop should arise, I would want the brake booster active.

Here is the block diagram of the brake vacuum system.

The most difficult part of the installation is finding the location where everything fits in the available space. The vacuum pump and reservoir are in front of the batteries, near the front bumper.

The relays are mounted next to the 12 volt battery.

This is the fitting that connects to the brake booster at the master cylinder.  The size is 12 mm and the vacuum kit is 3/8 inch.  I was able to use some of the existing metric vacuum hose and attach it to a 1/2 inch to 3/8 inch reducing barbed hose coupler.

The vacuum kit didn't come with enough vacuum hose for my installation, and at the pressure switch you can see that I switched to a blue vacuum hose.

The pump makes a small whirling or hum sound for a second or two as it pulls a vacuum. The pump turns on after every 2 or 3 presses of the brake pedal. Above 15 MPH, road noise drowns out the sound of the pump and I can’t hear the pump at all.  I understand that VBS now makes a piston pump that draws less power, and is even quieter.

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