October 2015 – Mustang Power Disc Brake Installation
Early Mustangs were available with manual drum brakes, power drum brakes, and manual disc brakes for the front wheels, but not power disc brakes. I’m not sure why they didn’t offer a power disc brake setup, it’s no more complicated to add a power booster to a car with front disc brakes, but they didn’t. Thanks to the great aftermarket interest in these cars and the enthusiast support, there are several power front disc packages available. I chose the kit from SSBC because it most closely matches the original disc setup but adds the power booster and a dual-circuit master cylinder.
Dual-circuit brake systems were federally mandated starting in 1967, and they’re a huge safety upgrade. A dual-circuit system splits the braking system into two completely separate parts, usually front and rear, so that if you experience a brake failure at one wheel, you still have two wheels with functioning brakes. If you experience a failure anywhere in a single-circuit system, you lose everything. That was actually Henry Ford’s rationale for not adopting hydraulic brakes until well after all the other automakers had done so. He held mightily to the mechanical brake concept, “the safety of steel from pedal to wheel.” If you lost a brake rod or broke a brake cable, you still had three wheels with brakes. With hydraulic brakes, if you lost hydraulic pressure, you lost all your brakes at once.
I’d installed the rotors several months ago when I moved the car into the garage, but I hadn’t installed the calipers, the master cylinder, or the power booster until recently. Installing the calipers was super easy. They bolt right up, just like the factory ones did, except these have stainless steel pistons and bores, so they won’t stick like the factory ones used to.
Installing the master and filling the system wasn’t without its problems. Bench bleeding the master, which is both recommended by the manufacturer and a generally good idea, was easy. Installing the booster was a pain. There’s no room to work, so the only way to tighten the nuts that hold the booster to the firewall is by using short stubby wrenches…10 degrees of swing every time. It took forever! If I hadn’t been able to climb into the engine compartment it would’ve taken even longer.
To top it all off, once I’d gotten everything hooked up and bled each wheel, I had a somewhat firm pedal that would slowly sink to the floor (the sign of a leak). I was not happy. Quite quickly I found that the connection at the distribution block from the master cylinder was leaking, so I tightened it. Still leaking when I put on the brakes, I tried again. I’m wary of over-tightening flare connections, having already done it too many times on the Packard, so I loosened the line and then re-tightened it in the hope it would seat properly. No dice. I pulled the line out to look for cracks or flare issues, but found none. I took pictures with my phone to see if I could detect any dirt or a crack in the distribution block. Nothing. I put the line back in and tightened it down again…still leaking. I put teflon tape on it…still leaking. Finally I threw in the towel and ordered another distribution block from NPD, which arrived a day later (they are just plain awesome).
The new block? Perfect. I took out the old one, popped the lines into the new one, and bingo! No leaks. The so-called old one was new as well, I’d purchased it just a few weeks earlier, so I’ll return it the next time I’m at NPD. And now the Mustang has brakes! One system complete!