Mr. Green Car: Maintaining your older vehicle: Brakes–part one
By Allen Penticoff
I write occasionally about vehicle maintenance topics because a survey by The Rock River Times once determined readers were interested in keeping their existing vehicles maintained rather than reading about new cars they can’t afford. So, I try to mix things up and write about both.
It is hard to ignore what is new and exciting. Then again, there are only so many stories in vehicle care to write without getting repetitious. This week, the green connection in maintaining your older vehicle has to do with the braking system. Plenty of good old cars and trucks out there—not disposing of them is a good thing. “Reduce, reuse, recycle” applies to vehicles as well. Not getting rid of something in the first place should lead the three Rs, but there is no “R” for it, so reuse and keep using are considered the same.
There are only two styles of brakes: “disc brakes” where a caliper pushes pads against a spinning steel rotor or “disc” and drum style, where brake “shoes” are housed inside a steel “drum” and are forced outward against the inside of the drum. Your vehicle’s braking system is hydraulic. When you press on the brake pedal, you are pressing a lever that pushes against a small piston in the “master cylinder.” This creates a very high pressure that is applied to brake fluid. Since fluids cannot be compressed, the pressure moves through solid steel and flexible steel/rubber lines to the brake calipers and/or drum “wheel cylinders,” where brake pads are pressed against rotors or drums. The friction of this process causes the vehicle to slow down and stop. It is an amazingly simple system, until you add the modern complexity of anti-lock brakes that sense the wheels not turning and release some pressure so the wheels don’t lock up and cause a slide.
Brake fluid itself is an unusual chemical. The most common brake fluids are Department of Transportation (DOT) rated—DOT 3, 4 and 5.1 fluids based on a glycol-ether rather than oil. These fluids can absorb water, so the fluids have corrosion inhibitors in them. A newer silicone-based fluid (DOT 5) does not absorb water. However, you must use what the vehicle manufacturer recommends as the seals are designed to be compatible with specific fluids.
The fluids must be very heat resistant and still be thin and flow freely at low temperatures. Since the glycol-ether based fluids absorb water, it is recommended you use only a newly opened container of brake fluid to replenish lost fluid. It is also recommended that you replace all the brake fluid with new every few years as the fluid will absorb water over time, the corrosion inhibitors wear off and leave the system susceptible to boiling under heavy braking or corrosion and line failure. But honestly, this is rarely done, despite being great advice. Brake fluid can damage paint, so be careful with it.
In the course of my vehicle use, I’ve had several brake failures, so I can tell you it does happen. I’ll describe some of the instances here.
On my 1987 VW Vanagon Camper, the right rear brake started dragging badly, probably because of an internal collapse of a flexible line. I ignored this/did not notice until one day, just as I came home from a short trip, the brake pedal went soft, and then as I stopped in the driveway, the brake pedal went to the floor. I looked for a broken line or blown wheel cylinder seal, but saw no fluid dripping anywhere. A few days later, the brakes seemed to be fine. I was very perplexed.
I went to see some Volkswagen gurus and had them have a look at the brakes. They found the dragging brake and said it was so bad, it was causing the drum to heat up the brake system to the point that the fluid had boiled. Once it is boiling (and the more water in the system, the easier it is for it to boil) vapor is created, and the hydraulic system cannot function with a compressible gas—air or other gas in it. Brakes are “bled” to rid them of air. If a tiny amount of air is in the system, you can pump the brakes to compress the air to the point the brakes will work, but it’s not good to go on like that. Get the problem fixed. With the VW, the gurus said it was totally not safe to drive it, despite what appeared to be functional brakes. This repair job still awaits me.
The steel lines of the brake system are prone to internal and external corrosion. In our area, external corrosion is the bigger problem. Salt used in the winter is very bad on the steel. The lines are often routed through areas that trap moisture, compounding the problem. This is why I wash under vehicles in the winter religiously. Doing so greatly extends the life of the fuel and brake lines located there. I’ve had three brake lines fail (rupture) because of rust eating through the thin steel wall of the tubing. When a vehicle nears 20 years old, start having a hard look at the lines. If they look bad, they should be replaced before a failure occurs. Fortunately, most modern brake systems have a double master cylinder system that creates two independent brake systems. The left front brake is paired with the right rear brake, and the opposite brakes are paired so that if one “system” experiences a failure, the other one will still work to stop the vehicle. Half a system does not work very well, and if a sudden loss of brake pressure occurs, do not drive any farther than necessary.
My 1990 Suburban had a weird problem with one front wheel locking up during even moderately heavy braking or on wet roads. I lived with this a long time, as I could not comprehend why this was happening. I found out why after a line failed 20 miles into a vacation trip at night while towing a large boat on a holiday weekend. The rusty line had been bulging, releasing pressure. The opposite wheel, getting all the pressure, would lock up while I pressed for the vehicle to stop. I was essentially trying to stop with half a system. Not easily repairable, our vacation plans were radically altered. Replacing the failed line made the brake-locking problem disappear.
Brake line replacement work is dirty, difficult work under a vehicle. I’ve done a few and can’t say it is anything I look forward to. Repair shops can charge several hundred dollars for this kind of work, and it is justified. It depends on where the failure occurred. The parts are inexpensive, but the labor can be considerable. Brake parts are often rusty and fail when worked on, leading to expense when an otherwise functioning part needs to be replaced because of a broken bleeder or frozen/broken line nut. New vehicles have plastic-coated lines, but replacement lines are usually bare steel. While stainless steel replacement lines are available, they are expensive and not common to see in new vehicles, although it would be a great idea.
In part two, I’ll go further into money-saving advice related to brakes.
From the May 5-11, 2010 issue