QuestionQUESTION: I recently added a power brake booster to my 63 Studebaker Lark (all drum)brake system. The booster was from a 67 Rambler Ambassador and mounted up beautifully to the firewall and the Rambler master cylinder was exactly the same as the Studebaker. After installing, I also replace the two front wheel cylinders (sticking and leaking slightly) but the back w/c were fine and the shoes were good. Now that everything is back together, the brakes are extremely sensitive - I mean face into the windshield touchy! The M/C is a duel and I robbed the distribution block from the Rambler when I nabbed the booster but I have not installed it yet. Would adding it help solve the problem? I know that drum brakes are self-actuating and I have read that this makes them easy to lock up when adding a booster but when I drive it, it seems more like hitting the brakes is like an off/off switch - it's all or nothing - no slowing down - just stopping. I have been reading everything I can find online, one source says add a distribution block, another says switch to a disk brake master cylinder, another says it all in adjusting the rod to the pedal and from the booster to the M/C (tried that - it didn't work). Rather than wasting alot of time and money buying and replacing parts, can you tell me what would be the most logical path to resolving this issue? I know you could get a new Studebaker with power drum brakes and I know that the Rambler I took the booster from had all drums, so there has got to be a simple answer to this one? Studebaker and Rambler had it figured out - so there IS a way! Thank SOOO much for your help!!
ANSWER: Boy you guys out there sure come up with problems that make the old gray matter steam a little. Ok, now if my memory serves me right the booster that you are using has vacuum applied to the diaphragm all the time the brakes are in the released position. When pressure is applied to the brake pedal a valve in the booster overcomes spring pressure and vents one side of the diaphragm, the one closest to the fire wall, allowing a differential of pressure, vacuum on side and atmosphere on the other side, to assist in applying the brakes. It would appear to me that the problem is more in this valuing that in the hydraulic side of the brakes. To check this disconnect the vacuum line from the booster and drive the car carefully in a safe area and see if the brakes are controllable albeit more pedal pressure. If the brakes will modulate well then the problem is in the vacuum side. The distribution block that you are talking about is a proportioning valve that adjust the hydraulic pressure front to rear. It should be installed but I don't think that is the entire problem. Good luck and let me know.
Brad
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QUESTION: Hi Brad,
Thanks so much for your input. You are correct in your assessment of how the booster works. I have tested the booster with the common tests (brakes pump up firm with the engine off and pressure is released with the foot on the pedal at engine start up and pedal is hard as a rock and difficult to stop when disconnected from the vacuum source. I spent a hot, humid Savannah Saturday installing the distribution block and bleeding the brakes; one of which did improved the braking situation. Interestingly, upon the first test drive, one of the brake line crimps I had made at the fitting was leaking slightly. On the road, the brakes felt great for the first few stops with just enough "resistance" on the pedal to make the car stops as well as my 2005 model cars! To say the least, I was feeling pretty darn impressed with myself until I continued on the test drive and gradually it became harder and harder to bring the car to a complete stop (as excess fluid was being force out the leak instead of pressurizing the wheel cylinders). I never lost enough fluid to make the braking spongy; just enough to make coming to a complete stop take about 4 extra feet. Returning home and checking the pipes again revealed the leaking fitting. Once that was repaired, the second test brought things back alittle more to the original condition with less "resistance" and "feel" to the pedel, but I still must depress the brakes slowly to avoid a face full of dash board! The original stopping characteristics of the car's brakes before the booster was added can be noticed again! I really believe that my problem is related to too much fluid pressure going to (at least) the front wheel cylinders. I have since read that it is sometimes a good idea to install a disk brake master cylinder with a bigger bore to loose the "touchy" brake feeling, so I might give that a try when the weather cools down a bit OR I am playing with the idea of just switching over to a front disk brake kits that are all the rage these days. Personally, I have never been a big fan of "customizing" in such a manner or spending the $500.00 plus on the kit for this car, however, I am finding it increasingly difficult to enjoy the car in modern traffic with the full none powered drum brakes and among drivers who are not sympathetic to the fact that I am driving a 40 + year old car that can't stop like their 2006 Honda Accord! So my mind is being forced open to the idea. Either was, its all about the fun of making it work for me and trying to make the car as much fun and as safe to drive and enjoy as possible while keeping that original look. I will keep you informed of how it goes and I would be interested to hear about any input from you or readers who might have worked through a similar situation. Thanks again for your advice and keep up the great work! It's all great fun to read and share our experiences!! -Brian, Savannah GA
AnswerGoodmorning Brian:
One of the few modifications that I like when dealing with old cars is updating the braking system. In fact my 41 Ford coupe has front disc brakes as a safety precaution. Changing the master cylinder might work but it seams to this old mind that a smaller bore master would be the thing not a larger bore. I don't know but I would check a physics book for mechanical advantage and pressures. By the way I hope that you have double flared the brake lines because anything less will surely leak. Good luck and keep me posted.
Brad
