Project Car Diaries: When Upgrading an Old Car’s Brakes Turns Dangerous

I found myself having to push the pedal exceptionally hard to get the car to stop. That initially led me to bleed the entire brake system, then to check for collapsed hoses and clogged lines, and even bench bleeding the master cylinder and even swapping to another unit altogether.

No matter what I did, the brakes simply didn’t do their job as well as they should, forcing me to test and make adjustments enough times to make anyone nuts. And on what would become a final run, I got the car stopping decently well. That’s when disaster nearly struck. 

After adjusting the proportioning valve, I panic-stopped at a speed of 30 miles per hour. Then there was a pop, and my foot slammed to the floor. Only the car didn’t stop. Something within the Right Stuff power brake conversion had failed. I had to use the parking brake to slow the car to a halt. 

Luckily, this happened on the quiet street I live on and the car eventually came to a stop without harm. Still, it serves as a prime example as to why you should think twice before you go modifying your car. Especially something as necessary as your brakes. 

What had happened was the pushrod linking the brake pedal to the booster had snapped. Upon closer inspection, I found it to be constructed with very thin walls. I can understand saving costs in some areas, but, in my humble opinion, this is a recipe for disaster and I only narrowly avoided that. I’m no engineer, though. So, I decided to call up Right Stuff and see if they could offer an explanation as to what happened.

The person I was talking to brought up an excellent point. The conversion system I’m using is designed to work with the pedal ratio of a manual brake system. If you try to run it with a car originally equipped with power brakes, you can run into serious problems. 

Here’s where things get complicated. My 1969 Dodge Charger is a lifelong hotrod that’s been modified by at least two people before yours truly: my father, and the guy who had been working on it before him. By the time I got it, the factory brake booster was long gone along with the 318 and automatic transmission it was born with. There’s no way of knowing what assembly I have without comparing it to another car, which I never even thought to do. 

The failure of that pushrod could very well be due to my own ignorance. However, the rep I was speaking with did say they’ve never heard of that component failing. In this situation, typically the booster itself is what goes. It’s also a second-hand part, adding even more speculation. 

After the booster failed, I promptly switched back to manual brakes. I noticed that the pedal didn't come all the way to the top of the stroke, and I decided to order up an adjustable brake pushrod from Amazon. Naturally, disaster struck twice. Thankfully, in a much more controlled manner this time. 

After making the swap and running through the adjustments, the pedal started to feel softer and softer. Finally, I decided to see if the pedal felt soft all the way through compression, signaling air in the lines. My foot did go all the way to the floor with ease, but the pedal never came back up. 

Upon closer inspection, I found the very pushrod I'd swapped in had bent like a wet noodle. 

At this point, the conclusion that I've ultimately come to is that I am indeed bottoming out the master cylinder, causing excess stress on the components, leading to their failure. I can't find any signs or indications to say otherwise.

I firmly believe that the parts that are failing should have been built better from the get-go. I'm not a World's Strongest Man contender, and they're still breaking with relative ease. But even if I were Hulking out on the brake pedal, these components should withstand that tremendous pressure. Lives are at stake here. Still, it's unfair to lay blame on any particular component when I didn't do my fair share of homework before installing these parts. 

What happened to me was an easily avoidable mistake that could have put me and innocent bystanders into trouble. I’m lucky that it happened where it did, and I feel that it’s my responsibility to use that fortune as a reminder to someone out there that they should really think twice before they go about altering their car. 

I can’t just assume I know everything about my project without thoroughly investigating every inch of it. No matter what manufacturer produced it or the parts I used, it became my responsibility in its entirety the minute I started making changes. Because as soon as I altered things, the effectiveness of the combination the originators came up with started to diminish and it’s up to me to figure out what works based on the modifications I’ve made. It’s on all of us to own this responsibility.

Don’t just trust anyone, either. Don’t forget that aftermarket manufacturers are in the business of selling parts. They’re going to tell you something is the greatest thing since grilled cheese, even if it isn’t. Research the brand, see what others are saying, and make sure anyone you take advice from uses the part just as you intend to. In a world where so many cars are limited to being trailered around, there’s no promise that the parts you’re using are built to take much more than that. 

Lastly, and most importantly, test your car safely. Don’t just put things together and assume they’re going to work, no matter how much you think something through. You might have forgotten something or used a bad part, and there’s no shortage of ways for things to go wrong. Find a safe place to test it out before you hit public roads. Skipping that step is how small hiccups like this could easily turn into a total catastrophe. 

All of that heartache put me in a loop that brought me back to the master cylinder and brake pushrod combination that both my father and I had driven with for years. If it ain't broke, don't fix it, right? You can count on me test-cycling the brake pedal a hundred times after I finish typing this out, even though I've already done it countless times. 

Other than this, things have honestly been going smoothly. The Charger runs and drives almost scarily well. It's getting harder and harder to believe that it was once common field trash. And though these growing pains are intense, they are what will make the car a respectable driver. 

That doesn't mean it's all good, though. I've recently found the source of yet another vibration in the driveline. Turns out I've got a nice bend in my driveshaft. The solution? A new differential. Obviously. As it turns out, finding a replacement driveshaft is a bit of a chore for this old car. So, one thing led to another, and I snagged myself an 8 3/4. It may not be a Dana, but its versatility will change the life of this car for the better. Stay tuned for that chapter of this ongoing saga.