The Braking System Part 1
by David C. Grainger
President, The Guild of Automotive Restorers
Here's a few tips on brakes and the braking system in your old cars. I have been the driver of more than one vehicle that has had a complete brake failure and it is an experience that I would rather like to save others from.
Really old cars with mechanical brakes are actually less prone to complete brake failures than cars equipped with hydraulic systems. They are not immune however and even at the best of times they do not stop a car all that efficiently. Probably one of the largest problems with mechanical brake systems is that they need to be adjusted frequently and this is something that many current owners sometimes forget or just don't know. As these systems are used the shoes wear as do the drums themselves. Often the shoes wear at different rates because the individual brakes wear differently or are a little or a lot out of adjust to start with. What happens as the shoes wear is that the brake pedal gets nearer and nearer to the floor. Uneven wear is exhibited by pulling to one side or the other. If these conditions are noticed it is time to get out your owners hand book and make the required adjustments. The brake pedal does not descend to the floor dramatically as with hydraulic systems and you may not notice that the pedal is getting lower gradually but during an emergency stop you may find that there is just not sufficient pedal travel to jam the shoes hard enough against the drums to get you out of trouble even though in normal driving you seemed to be able to stop just fine. Pedal height should be fairly high but you should have a half inch to an inch of free play at the top so that you know that your brakes are not dragging. Different cars have different methods of adjusting the brakes but they are usually all done with nuts or adjusters on the backing plate. Your manual will give you the information that you need. If you take the car to a garage for brake adjustments make sure that they know what they are doing or supply them with a manual or specifications sheets.
You should also adjust the brakes with all of the wheels or at minimum the fronts or the backs off the ground at the same time. Don't do one, then drop the car and move to the next because you won't be able to determine if they are all adjusted the same. Generally you adjust the brake until you can not turn the wheel by hand and then back it off until the wheel just starts to rotate freely with no shoe drag. Make sure that it rotates with no drag in both directions. After you have adjusted all of the brakes get a friend to sit in the car and operate the brake pedal as you manually spin the tire and watch to see if there is a smooth and equal application on all wheels. If with the pedal down you can still move a wheel, even a little it is well out of adjust. Also, if you notice that one stops spinning much faster than the others, it is also out of adjust and needs backing off a little. Let the final word on your car's individual brake system come from the owner's handbook. Don't just assume it's is correct because there are lots of quirky little things that occur with a lot of the old brake systems that are often described in the manuals. Mechanical brake systems also require grease and oiling and if this needs to be done in proximity to the shoes and drum make sure that you only use enough to do the job properly. I have seen grease and oil from the eccentric cams contaminate the shoes and cause problems with binding and brake lining deterioration. While you are adjusting you brakes you should also check your axle seals to make sure that they are not leaking into the drum. Leaking seals will also cause some pretty severe braking problems and can cause total failure even in a mechanical system.
You will also need to check and lubricate all of the mechanical connections which extend from the base of the brake pedal. Most mechanical systems operate using a cross rod that usually runs from one side of the frame to the other. Make sure that it is properly lubricated and check for binding and wear. You should also check all of your long brake rods for rust and fatigue. They can bend and break and the clevice on each end needs to be checked thoroughly. Anywhere you detect cotter pins in your system make sure that they are healthy and not rusted. Anywhere you detect a hole without a cotter pin, you had better check to see if one is required and replace it if it is missing.
Hydraulic systems which are found from the early thirties on up have just about all of the same physical problems and a few more on top. Most early systems do need to be manually adjusted as the car is driven, although perhaps not with the regularity of the manual systems.
Hydraulic systems are more efficient than mechanical systems, that is a given, but they are also more prone to a catastrophic failure without giving you any warning.
There is nothing worse than putting on your brakes only to find that your pedal suddenly drops to the floorboards under your foot.
Early systems with single master cylinders are the most prone to this kind of failure. Even a two reservoir master usually only buys you a little time to get stopped. If you have a failure with a two reservoir system, don't be tempted to try to get home on what little brakes you have left. Often they are either inadequate or they are also on their way out.
The best way of making sure that you don't have a failure is regular and routine maintenance. This sounds elementary but you would be surprised at how often brake systems are abused without the owner even being aware of the abuse.
Just replacing shoes and turning drums is often not enough. Of course leaking cylinders, both the master and the wheel cylinders should always demand immediate attention, either being replaced or rebuilt. You can check for wheel leaks periodically by looking under the car and checking to see if you have any wet marks or stains running from the wheel across the tire. If you notice this condition, see to it immediately because it signifies a significant fluid loss and usually just precedes a complete failure.
The best way of making sure that you don't have a failure is regular and routine maintenance. This sounds elementary but you would be surprised at how often brake systems are abused without the owner even being aware of the abuse. Just replacing shoes and turning drums is often not enough. Of course leaking cylinders, both the master and the wheel cylinders should always demand immediate attention, either being replaced or rebuilt. You can check for wheel leaks periodically by looking under the car and checking to see if you have any wet marks or stains running from the wheel across the tire. If you notice this condition, see to it immediately because it signifies a significant fluid loss and usually just precedes a complete failure.
You should also check you fluid level in you master with fair regularity and if it needs topping up you should immediately check for leaks. Many leaks are slow seeps from couplings, proportioning valves or the cylinders themselves and the lines are subject to pinholing from rust and kinking and can seep for a while before leading up to a complete failure.
One item that is most often ignored both by owner and also by mechanics is that the brake fluid itself should be changed on occasion. Usually people tend to think that if the master is topped up everything is fine, but there are some nasty things that happen inside your brake system every time you put the car away for the winter.
The culprit is water and it appears in your system through condensation. What often occurs is that water, which is sucked up by brake fluid quite happily and then held in suspension for a while, will precipitate out of the brake fluid during periods when the brakes are not being used. What occurs then is that the water collects under the brake fluid and lays in the steel lines, causing corrosion which will at least cause rust contamination which will erode rubber seals and roughen cylinder bores so that they leak and at worst, cause brake lines to fail entirely. I have seen brake lines that have looked as if someone unzipped them along their bottoms. What is astounding is that their condition had remained undiagnosed until an emergency stop caused them to burst from one end to the other. Another common problem with condensation damage in brake systems is found in the cylinders themselves where water collects under the brake fluid and corrodes the smooth bore of the cylinder so badly that it will not seal or operate properly. This condition is often so bad that the cylinders have to be thrown out or re-sleeved as they can't be honed out and made useable. Changing the fluid and bleeding the brakes through will eliminate contaminated fluid and rid your system of condensation.
One final tip. Never use brake fluid that has been opened and then left sitting around. It really does act like a sponge and will readily absorb moisture from the air. Always use fresh fluid. Brake fluid is packaged under very stringent humidity controlled conditions for the above reasons and as soon as you open up the can or bottle, that fluid has begun to spoil. You should never try to recycle it either. Both using previously opened cans or trying to capture and reuse fluid during brake bleeding are both false economies which can turn around and haunt you later.