ElectroClassic EV
Classic Cars Reborn into the Electric Future

Brake Dance

One remaining and formidable task is a total reassembly of the brake system.  All four brake calipers had previously been rebuilt, but after a number of frustrations during the install, I called Eric at PMB Performance for some perspective. Teeners in the forums hold PMB as the gold standard for classic Porsche brake restoration, and my conversation with Eric confirmed this claim.  A short 10 minutes on the phone convinced me that I wanted a set of his brakes in my car.  PMB separates the caliper halves, media blasts and then yellow zinc anodizes them inside and out, insuring they will outlast any painted caliper.  I’ll be sacrificing my red shoe look, but will gain a classier gold appearance that is closer to stock, as seen above.

My installation started with the wheel rotors.  One front brake disc rotor was quite rusty from sitting unused for so long, so I dropped it at Engler Brothers to be machine turned.  The other disc had worn too thin, so I replaced it with a new front rotor purchased from Otto’s Venice.  Luckily, the rear rotors had only minor surface rust and still plenty of meat on the discs.  Rather than resurface them, I opted to polish them with some emery cloth, mask them, apply a coat of Rust Reformer, a coat of black epoxy paint, and then reinstall.

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The rear calipers easily bolted right onto the axle hubs, and the fresh brake pads clipped smoothly into their slots without complaint.  However, both front rotors were discovered to be pre-1973, which fit incorrectly and made it impossible to mount the front brakes.  I headed back to Otto’s to exchange the wrong rotor for a correct later model one, and then ordered the other online.  After drifting new bearing races into the hubs, the new front rotors fit perfectly and the brakes mounted without a hitch.

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The brake retaining pins and expanding springs were cleaned up and given a shot of cold galvanizing compound to keep them rust-free.  I can’t vouch for how they will hold up to heat, but the regenerative braking should leave the pads cool nonetheless.  Fresh emergency brake cables were installed to eliminate any stretchiness in the old pair.  They were also purchased from PMB and included the rubber accordion boot.  The end yoke of the emergency brake cable is visible at frame right above.

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Since the existing rubber brake hoses were quite old, a complete set of four was ordered online from Auto Atlanta, in addition to a new 3-way fitting for the junction of both front brake lines at the master cylinder.  Some of the threaded ends of the metal brake lines also appeared a bit corroded, so I replaced about half of them.  Many of the exact lengths I needed with the Euro-style “bubble flair” and metric thread were available at various auto parts stores around town.

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The original brake master cylinder was pretty much toast, so a replacement was purchased.  New master cylinders are always a bit spendy, but knowing it’s factory fresh feels good.  Installing it was pretty straightforward, but involved raising the front end of the car to provide access to the underside of the pedal cluster.  I applied a little white lithium grease on the end of the brake pedal plunger where it seats in the master cylinder.  I then squeezed a small bead of silicon sealant around the edge of the hole where the master cylinder passes through the floor, so the flange has a water-tight seal when seated, as seen above.  The image also shows the special 3-way brass fitting that divides the front brake circuit between the left and right disc calipers.

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The plastic fluid feed hoses were in good shape, but the metal shorties needed some scrubbing and a coat of clear to protect them.  It’s a bit tricky getting the metal ends of the feed tubes through the trunk holes and properly seated in the master cylinder grommets.  I found it easiest to hang the master cylinder on the mounting studs and only loosely thread the nuts.  This gave enough play to wiggle the feed tubes into the top of the master cylinder and firmly seat them before torquing down the cylinder mounting nuts.  Note that the slightly shorter plastic feed tube passes through the hole nearest to the driver side front wheel.

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The brake pressure regulator is a very important component of the braking system.  It’s purpose is to reduce pressure on the rear wheels during hard braking, eliminating the potential for the rear wheels to lock and cause a tailspin.  The regulator uses an internal valve to keep front and rear brake fluid pressure equal until it exceeds a predetermined PSI, called the “knee point.”  Beyond that, the regulator drops the rear circuit fluid pressure along a linear path as the front brake pressure increases.  In extreme cases, the rear brakes would never lock up before the front, allowing the back end of the vehicle to maintain road grip.  Here’s a link to some nifty diagrams which are worth a thousand words.  There is overwhelming testimony that brake regulators rarely go bad, but because mine didn’t look original, I ordered a used one from Auto Atlanta.

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The next step is to bleed those suckers.  My first experiences bleeding brakes involved an empty mayonnaise jar, a rubber hose, a box wrench, and a willing assistant.  I bled brakes quite often, but assistants weren’t always available, so my discovery of the one-man bleeder hose was a revelation.  The basic setup includes a hose with an attached spring valve that only allows fluid to exit the caliper, and prevents air from reentering.  The most current version is called a speed bleeder, which builds a one-way valve right into the bleeder nipple, and is available for most cars.  One speed bleeder permanently installed on each brake caliper makes short work of removing air bubbles from the brake lines, but you’ll still need a flexible hose and some sort of container for the spent brake fluid.

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As you can, see my catch container was an empty bleach jug. Since I was starting with a completely dry system, I planned to circulate more fluid than a mayonnaise jar could hold.  The full jug can conveniently be dropped at hazardous household recycling when the job is done.  Bleeding instructions normally start with the caliper furthest from the master cylinder, and work closer one by one.  I slipped a clear vinyl hose on the speed bleeder nipple at the right rear caliper, and opened it about a quarter turn.  After about 10 minutes of pumping the brake pedal and refilling the reservoir, I began to see fluid at the bleeder.  Moving to the other calipers, I also started seeing fluid after a just couple minutes of pumping.  The clear vinyl hose allowed me to immediately see any air bubbles exiting the bleeder.  When the fluid is clear and bubble-free, all air has been expelled and the bleeder can be closed.

** NOTE  Fluid pressure is solely what raises the ball bearing from its seat in the speed bleeder valve, and allows fluid and air to exit the nipple.  Make sure that your speed bleeders are not passing fluid when there is no pressure on the brake pedal.  Check by holding a paper towel under the dry speed bleeder, open it a quarter turn, and look for fluid to leak out.  If so, the bleeders are malfunctioning and will be allowing air to also reenter the caliper when there is no pedal pressure (three of mine did this).  The result is sponginess in the brake pedal that will persist no matter how much fluid is circulated.  I ordered two new pair of Russell 7mm speed bleeders from an online retailer to replace the faulty ones.  Finally, these behaved as advertised.

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The final step is adjusting the resting gap between the pads and the disc, otherwise known as the venting clearance.  Only the rear brakes need this, as the front brakes have a built-in automatic adjuster.  There is already a 914World picture tutorial on this procedure by Eric at PMB Performance, so I’m not going to go into too much detail here, other than saying that adjustments need to be made with a 4mm Allen driver on both inner and outer pads for each rear caliper when the brake pedal is at rest.  Shown above is the right rear outer adjustment screw and lock-nut.  Proper venting clearance allows for correct operation of the rear brakes relative to the front, and guarantees firm emergency brake action.

**NOTE – This entire procedure took about 6 weeks to complete, including time taken to rebuild brakes, turn disc rotors, track down, order and receive parts, install calipers, buy and replace brake lines and hoses, troubleshoot bleeders, reorder calipers and cables, swap in new calipers, bleed again and adjust venting clearance.  It has been the most complex part of this restore so far.  Whew!

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