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You are dropping off your kids at school and slow down your car as you approach a crowded turnout. As you push on the brake pedal your car responds slowly, and you quickly press harder to get your vehicle to stop.
That delayed response and spongy feel may indicate a more serious problem--air or moisture in your vehicle's brake lines. Inspection by a brake expert is critical to prevent possible brake failure.
“If you feel sponginess in the pedal, it could be because your rubber brake lines are going bad, or there is air in them,” said Tim Beachboard, owner of FedHill Brake Line, a Massachusetts-based company that supplies brake lines.
Brake lines carry the brake fluid to the brakes. They are the backbone of the hydraulic system that makes the car stop when the pedal is pressed, and any “play” or sloppiness in the pedal is a sign of a problem.
Most vehicles’ brake lines are made up of two types – metal tubing for strength and rigidity along the body, and reinforced rubber hoses where they need to flex, such as around the suspension.
“When metal lines go bad, you won’t feel any degradation in the pedal. Suddenly, you just have catastrophic failure, and the vehicle won’t stop,” he added.
The latter is rare and usually caused by excessive rust on the outside of the lines.
"Moisture develops in the brake lines because brake fluid attracts it," Beachboard said. It slowly seeps through the rubber hoses and into the system.
One sign of moisture in the lines is dark-colored brake fluid. Anyone concerned that brake fluid might be bad can do a simple visual check.
“Take the lid off the master cylinder for the brake system, and look at the fluid,” Beachboard said. “It should look light, like a light beer or a lager. If it’s dark, like a Guinness stout, then it’s time to replace it.”
Replacing the brake fluid in the vehicle’s system is something that should be performed every few years to prevent rusting the inside of the metal tubes and decreasing braking ability.
“The weak link in the system is the rubber tube,” Beachboard said. “The rubber hoses don’t last forever.”
The rubber brake lines are often cheap to replace with quality parts from local dealers or parts stores. Symptoms of a rubber brake line that needs to be replaced include a spongy feel to the brake pedal, rusty brake calipers or rust on the metal fittings at the ends of the rubber hoses.
“If you see any brackets on flex-lines broken, you’ve got a big problem,” he said, adding that without being held in place by the brackets, the flexible hoses can rub other parts of the vehicle and fail.
Beachboard recommends replacing flexible brake lines when rotors and calipers are replaced, as a general rule, and whenever the owner’s manual suggests it.
Metal lines can take a lot of abuse, but some wet climates–especially where salted roads and snow are common–will eventually cause rust on the metal lines.
Failure of metal brake lines is rare, but your dealer or mechanic can check them out for you.
“It requires a good visual inspection,” Beachboard said. “That’s the only preventative maintenance there is.”
Beachboard said, "The inspection should be performed by a dealer or mechanic specializing in brake repair." Most brake lines are made of steel, which does rust, though other materials are available.
Some drivers who take their cars on the track or drive them in extreme conditions can take advantage of alloys such as Cunifer, which is used by some manufacturers.
"Cunifer is a blend of copper, nickel and iron that won’t rust and remains strong," Beachboard said. Some stainless steel products are available as well, but they are difficult to initially work with and make seal due to the hardness of the metal.
- Metal brake lines should be visually inspected for rust on the outside by a brake specialist or dealer mechanic.
- Flexible rubber brake lines are the weak link in the brake system, but are inexpensive to replace and should be changed whenever calipers and rotors are, or when your vehicle’s manual dictates
- Check your owner’s manual for brake fluid requirements. Some vehicle experts recommend replacing it every two years
- Brake fluid can go “bad” and turns dark in color. Normal fluid color is light yellow.
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