If Brake Lines Rust, Why Make Them from Metal?

A brake line on a manual brake system has 900 to 1000 psi of pressure, while a brake line on a power-assisted brake system has 1,400 psi or more of pressure, depending on the vehicle. Brake lines are made from steel or nickel-copper and sometimes coated with polyvinylidene fluoride (PVF), so they can adequately handle the pressure put upon them. You must use compression fittings to splice two lines together or to convert from the metal line to the high-pressure rubber line that goes to the caliper.

Why Brake Lines Rust and Why You Can’t Use Rubber

All metal rusts sooner or later. Some, such as aluminum, take a long time to rust depending on other metals that are mixed in. When lines are coated with PVF, they last longer. However, PVF has its limitations. First, it only tolerates heat up to 338 degrees Fahrenheit, though in most cases, the brake line will never see that kind of heat. The coating tolerates stress and chemical corrosion well, which is very important in areas that use salt and other ice-melting chemicals—including bromine salt solutions—on the roads during the winter.

Rubber brake lines are more likely to break or leak because of dry rot or because a rock or another sharp object cut the line. If you ride over a high curb, you could easily damage a rubber line or even pull it off the vehicle.

Metal lines are stiff, so they don’t sag, and they are more resistant to breaking when you hit something with them. Additionally, metal lines are often run along the top of the frame because they won’t chafe from rubbing as easily as rubber lines do.

Repairing Rusted Brake Lines

You can repair the rusted brake line in one of two ways. The best way is to replace the entire brake line. That means you’ll need a tube bender and at least two compression fittings – one for each end of the new line. When you remove the old line, bend the new line in the same places you find a bend in the old line.

In a pinch, you can also cut out the rusted part and replace it with a new section of brake line. However, if one area is rusted, the rest of the line could be rusted, and you’ll just have to replace another section. For every section you add, you weaken the strength of the line where they connect at the compression fittings.

When you notice rusted brake lines and you replace the entire line, you should flush the brake system, replace the rubber lines, and then fill the system with brand new brake fluid. If any rust got inside the lines, it could reduce the amount of brake fluid to the calipers, thus reducing brake effectiveness.

To learn more about brakes and brake lines, visit BrakeSystemU.com.