brake lines

That depends on why a line needs to be replaced, where it is leaking, and how well you can reach in tight places. Most of the time a steel brake line is leaking because of rust. There is no point in trying to save part of it because it is too difficult to make double flares on rusted lines. Just unbolt it and replace end to end with multiple pieces of pre-manufactured lines and unions.

I do not know what you mean by "tools", but your set is not complete unless you have a double-flaring tool. I can describe how to use it, but it's much better to have someone show you, if you do not know already. When a clean steel line has a damaged section from crash damage or something similar, it is often easier to cut the bad part out, slide on two fittings, make a double flare on each end, then install a new section with a pair of unions. Never never ever use compression fittings on brake line. Those are fine for the sinks in your house, but not on brake lines where the pressure can easily pass 2000 psi. Compression fittings on brake line will land you in the middle of a lawsuit when the customer's loss of brakes results in a crash.

When you need to replace multiple lines that run parallel to each other, such as when the lines to the left rear and right rear both run under the left side of the car, always remove just one and replace that first, then do the other one. Too often we read here that someone pulled all the rusty lines off, then forgot which one runs to where.

The line nuts that have to be unbolted are made of real soft metal. Always use a line wrench, (aka flare-nut wrench), to loosen and tighten them. If a line is rusty, you can bet the nut is rusted to the line too. If you loosen the nut, the line will twist off. Do not attack it with penetrating oil. There must never be any hint of petroleum product anywhere near anything that touches brake fluid. That will cause rubber parts to swell. If just a few drops of engine oil, transmission fluid, power steering fluid, or axle grease gets into the brake fluid, the only acceptable repair is to replace every part that contains a rubber part that contacts the brake fluid. That repair can easily cost more than a car is worth, and if it has anti-lock brakes, the cost is even higher.

If you do not care about saving the old line, and are just interested in getting it off, but the nut is too badly rusted for your line wrench, use an air-powered cutoff tool or a hacksaw to cut the line close to the nut, then pound on a six-point socket. Some people use a Vise-Grip pliers, but I find the socket and ratchet to be much more effective.

If you are going to replace a rubber flex hose, they almost always attach to a steel line with those soft metal line nuts, and those are some of the first to rust tight to the line. The steel line might be fine yet, so the problem is to get the nut loose on it. Heat the nut with a small flame from an acetylene torch. Propane will not usually get it hot enough. Have a cup of water ready. Put the tip of the flame on the nut, but be prepared for the hose to explode. That is not because pressure builds up in the line. In fact, it cannot as long as the brake pedal is released. The rubber hose melts then squirts out of the really tight metal band crimped around the end of it. There will be some smoke too, and a little hot brake fluid. It is quite the attention-getter.

As soon as it pops, dribble the water on the line. Some will run onto the nut and cool it quickly and shrink it. You should be able to screw off the remaining end of the flex hose with a pliers on it and a line wrench on the nut. Now, if necessary, heat the nut again to expand it so you can turn it with the wrench. If you hear it squeak and squeal loudly as you turn it, that is the best sound you can hope for. That means it is no longer rusted tight. Keep turning it back and forth while spraying a little brake parts cleaner on it to wash out the rust. Remember, do not use any type of grease or lubricant on that nut.

It is not always necessary to bleed at the wheels after replacing a steel line. Leave the last connection loose, add fluid to the reservoir, leave the cap loose so vacuum does not develop that would hinder the flow of the fluid, then wait for the fluid to show up at the connection. Sometimes it is helpful to "irritate" the brake pedal a little, by hand, to get the flow started, then let gravity do the rest. I rarely resort to pedal-bleeding with a helper, but when people do, a lot of do-it-yourselfers and inexperienced mechanics cause more problems by pushing the brake pedal all the way to the floor. Doing that is okay on a car with a master cylinder that is less than about a year old, but after that, crud and corrosion build up in the lower halves of the bores where the pistons do not normally travel. Pushing the pedal to the floor runs the rubber lip seals over that crud and can rip them. The common symptom is a slowly-sinking brake pedal, and that often does not show up for two or three days. This can happen too when a driver is surprised by the sudden popped line. The normal reaction is to keep pushing the brake pedal in hopes something good will happen. For this type of repair, a lot of shops automatically include a new master cylinder in their estimates.

If you have to bleed at the wheels, there is no more distressful feeling as when the rusted bleeder screw snaps off! Do not use anything bigger than a quarter-inch-drive ratchet, and a six-point socket to turn it. If it will not come lose with one hand, pound around it on the casting. Most of the rust forms from water getting into the hole through the center of the bleeder screw. That is why you will often see rubber caps on them. Less rust forms in the threads because water cannot get in there. If deforming the casting with a hammer does not work, you may have to get the torch out again. Do not heat the casting. The metal will draw the heat away too quickly to be of any use. Heat the bleeder screw until it is orange. That will not take long. Next, pour some water on it. The shock will break it loose and the cold will shrink it. In the rare instance when this does not work, heat it orange a second time, then tap on the casting before hitting the screw with water.