I recently needed to do repairs to my axles, and in the process of removing the upper axle bolts (on the drums), I managed to shear my brake line off. Being optimistic, I called a few parts stores, and not one carried pre-bent lines. I was sure the dealership could help me out, but I couldn't bring myself to find out how much they would actually charge, so I didn't even call them.
A friend told me that he had a REALLY difficult time bending his own lines. I undertook this project with his warning in mind. What I found is that it is NOT hard at all to do it yourself. It is just absolutely imperative that you take your time, triple-check estimations on angle and length, and go as slow as you can stand. This write-up isn't how to bend SPECIFIC brake lines, as they are all shapes, angles, lengths, and such, but rather an assortment of tips that I came up with to ease my process.
First - Have the right tools
Bend brake lines with ONLY line bending tools. They are cheap (mine was $13), and easy to use. Flare brake lines ONLY with a flaring tool. You can rent them at your local Checker, Schuck's, or Kragen Parts stores (and possibly others, I didn't call around about the Tools). The one I have, I rented from Checker for a totally refundable $30 deposit.
My primary weapons:
The bender is a great tool. I don't have a lot of faith in off-brand tools, but I bought this one, and it worked GREAT. Powerbuilt brand, Checker Auto, $12.99.
My secondary weapon:
To measure the length of line between bends, I used a flexible sewing measuring tape (only because the wife, after watching me eyeball the lengths, got me hers out of the house... what a woman!). It worked great, but you could substitute any manner of measuring device, even a yardstick!
Second - Buy the correct length/diameter of line and correct thread count fittings
This step is self-explanatory, but this is also VERY important. Take a piece of line and a fitting to the parts store if you need to. Also, don't hesitate to bother the guys at the store until they let you match it up yourself if that makes you comfortable. And remember: Buying too long a piece is infinitely better than buying too little. I bought the longest one I could find, and I only ended up with about 2 inches of line on each end after the bends were all done!
Third - Bend and Measure WITH CARE
Forming your line is the whole point of the operation, so be sure to measure as precisely as possible, bend SLOWLY and CONTROLLED, and triple-check if you aren't totally positive. My tips:
Measuring - Don't just measure the straight part of the line, you have to include the length that the bend takes up. It's the only way to do it accurately. To this end, I have created a visual aid representing how I did it to create proper dimension carry-over.
Measure from apex to apex. Imagine that the line doesn't bend, rather that it continues straight until it meets the other straight piece of line. Their junction is your start point for accurate dimensions. Start with one point, then get the other. In the picture, you can see from my graphical addition that I plainly need 5 inches of line, from bend to bend. I used the edge of a screwdriver and, with LIGHT pressure, scored the line to get my dimension. You could also use a sharpie or some sort of marking device. A pencil might even work!
Bending - Make your mark circumvent the line completely if you can help it, as this will more easily facilitate the bending process. If your bender is like mine, it is dead easy to get the proper bend. Seat the line in the 2 outer guide sheaves and squeeze the handles to SEAT (for gripping, NOT bending) the die on the line. If you look at where the line seats in the die, you can see a definite center. Put your mark (on the line) in the center of the arc that contacts the line. This will make your mark the center of the bend, giving you exact dimension carry-over.
The quickest bend I did in this line probably took about 2.5 seconds of a slow, controlled squeeze. Go slow, slower is better, go slow, it can't be said enough. The fastest way to be going back to the parts store (in a totally bad mood, too) is to crank down on the bender and pinch bend your line in half. You don't need that, so just take your time and GO SLOW.
There are other low-end benders ($5-7), but the ones I saw looked as if they MIGHT pinch the line, so I bought the better one. I suggest getting the better bender for sheer peace-of-mind of a proper job.
Flaring - There are so many flaring kits, it's hard to give instructions or tips, but nonetheless, here goes: Be sure to use a fine file to round the outside edge of the line. It helps with cracking and irregular flaring. If double-flaring, be sure not to fully press the flaring adapter all the way into the line, just put a bit of pressure on it. Most of the flare is done by the flaring yoke itself. And, put your fittings on the line (in the proper direction) BEFORE you flare.
On flaring, just read and closely follow the directions included in the kit. It's your safest bet.
Fourth - You CAN make minor corrections
After all the bending is done, you may notice that a previous bend seems to be 1 or 2 degrees off from what you originally set. Although the bends you set are rigid, you can bend a SMALL amount by hand to correct this slight mis-alignment. Just be careful, and don't do it too hard or fast. If it looks like you are 10 degrees off, DON'T bend it by hand, just take the time to grab your bender and get your line properly bent.
Fifth - INSTALL!
When all is done, it's a good idea to mock it up to the place it will fit to see if you are in business, that way you can make minor bends and twists BEFORE you bolt and clamp it in place. If all looks well, and your flares are good, torque it in, clamp it down, bleed the line out, and pat yourself on the back!
This was my first time doing this, and a 4.5' section of line took me 50 minutes to bend and tweak to an absolutely PERFECT fit. And it only cost me $6 for a straight piece of line. I hope this helps shed a bit of light on this somewhat taboo maintenance subject!
Keep the wrenches turning and the wheels crawling!