Steel Brake Line Repair

The ability to stop your vehicle is a nice safety feature that we take for granted most of the time. Once that ability is compromised, one tends to appreciate it just a bit more. There is nothing worse that the awful, sick feeling when you mash on the brake pedal and your vehicle doesn't want to stop. Except for maybe that distinctive cacophony of sounds when you impact the car in front of you.

I lost much of my stopping ability not too long ago. I pushed on the pedal, and it almost hit the floor. I could stop the vehicle, but not like I used to. Quite a change from the normal action of my brakes. Immediately, I pulled over and checked my brake fluid level - almost empty. I added what brake fluid I carried into the reservoir, and gently drove home. "Gently" means keeping the vehicle in lower gear than normal to maximize the braking effect of the engine, and keeping a further distance back from the car in front of you than normal. The braking problem was on my 1985 Vanagon Crew Cab, and sure didn't want to ruin my front bumper!

A few days went by before I had a chance to take care of the problem. Diagnosis was simple, thanks to the tell-tale damp stain of brake fluid under the left rear quarter of the van. After jacking up the rear and removing the tire, I was able to determine that the steel brake line along the rear trailing arm had a tiny rust pinhole, allowing the brake fluid to leak out. The "best" repair method would be to order a replacement, pre-bent line from the dealer. But I needed to haul some sheets of drywall that same afternoon, so I could not wait. The rust on the brake line seemed to be concentrated on one small section, so I decided to splice in a new section of line using a compression fitting.

Tools & Supplies Needed:
  • Tubing cutter (smallest possible)
  • 11mm flare-nut wrench
  • 7mm open-end or combination wrench
  • Sturdy jack and jack stands
  • 3/16" steel brake line with metric threaded fittings and "bubble flare" style ends
  • 3/16" compression fitting
  • 32oz can of brake fluid

    Before any work can start, make sure you have the proper size and style of brake line. Many of the "supermarket" auto parts stores sell brake lines in standard lengths, such as 6 inches, 1 foot, 2 feet, etc. Get a line that is at least as long as you expect. I always buy the really long ones, since the price difference between a 1 and a 4-footer is usually less than a buck. Having some extra laying around the garage may save you a trip next time! Be careful of the fittings on the ends - you need to make sure that threads are metric. Also, look closely at the flare on the end of the brake line - there are 2 different types you could find. The type needed on a Volkswagen is known as a "bubble flare". Most American and some other imports use a "double flare" on the end. They are not interchangeable! If you install the wrong type, the brake fluid may leak out, causing you to loose that wonderful stopping ability.

    Brake lines Brake lines
    Looking at the photo on the left, the bubble flare is on the top, and the double flare (with the purple tape) is on the bottom. The photo on the right shows another angle - the double flare on the left, and the bubble flare line on the right.

    Wheel cylinder

    Now that we have the right brake line, the work can begin. First, loosen the rear lug nuts. Jack up and secure the Vanagon so that the rear tire is off the ground. Remove the tire from the drum, and set it aside. Using the 11mm flare-nut wrench, loosen and unthread the brake line fitting until it spins free from the wheel cylinder. You may find it easier to reach if you first remove the bleeder valve with a 7mm wrench. Be careful not to break off the bleeder valve or brake line fitting, or you will need to replace the wheel cylinder (more work!). The photo to the left shows both the bleeder valve and brake line attached to a new (uninstalled) wheel cylinder.

    brake line into wheel cylinder

    Use the tubing cutter to cut off the rusty section of the steel line. In a real emergency, you can use a hacksaw to accomplish the same thing. Pump the brake pedal a few times to flush any metal particles out of the line. Using the old piece of brake line as a template, cut and bend a suitable replacement. The end with the bubble flare and fitting will screw directly into the wheel cylinder, as seen to the left.

    Compression fitting

    A compression fitting is used to splice the line together, seen here in the photo on the right. Compression fittings are a handy way to join cut ends of lines together. In a perfect world, we would either buy the pre-bent dealer part, or make a replacement line ourselves, including the bubble flare on each end. You can get a flare tool for steel tube that will produce a acceptable bubble flare for less than $50, but it is a pain to use. Compression fittings are less than $2 each, and work nearly as well.

    Fitting parts
    The components of the fitting can be seen in the photo to the left. Compression nuts, followed by small brass sleeves are slipped over each end of the line. These will fit into the compression union, shown in the center.

    Assembled fitting
    As each of the compression nuts are tightened on the union, the brass sleeves are forced into tapered recesses inside both the union and nuts. The tapers squeeze the sleeve hard enough to form a tight seal that is capable of withstanding several hundred PSI.

    Repaired line

    Once the fittings are tightened, bleed the brakes to get any of the air out of the system. I only had to bleed the rears, since my Vanagon has dual-circuit brakes. In other words, air had only gotten into the rear braking circuit. Pre 1968 VW's had single circuit brakes. If any air enters the system on those, front and rear brakes both have to be bled. Once the brakes are purged of air, have an assistant push hard on the brake pedal and hold it down while you check for leaks at both the threaded and compression fitting. If there are no leaks, put the tire back on and hit the road!


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