I have been repairing brake lines on cars and trucks for over thirty years now and it is a job that never gets easier. It never ceases to amaze me how cheap the metal is which they use for our brake lines. I am most dismayed that even the newer cars and trucks still use such low grade metal for the brake lines. It aggravates me that the fuel lines are stainless steel wherever they are not plastic and yet the thing that stops your car from hitting a tree can still be made from such inferior cheap rusty steel.
From work experience I know quite a bit about the process used in making the actual tubing which brake lines are made from. I did some water treatment projects at a few of the automotive plants where they make the metal lines. These are fabricated from a flat strip of steel stored on a roll that is fed into a machine that cleans the metal then rolls it into the tubing from its original flat shape and then it welds the seam shut on the fly. They now offer lines that are coated with rust inhibiting paint and the high end cars get these improved brake lines. So what do they put into the cars that most normal people can afford? Cheap rusty metal is what they still use!
One of the other things about brake lines which I find highly annoying is how the brake lines are usually routed in such a way as to make them impossible to even access let alone to replace them back to their existing locations. The best you can hope for is to put them close to where they once were. Anti-lock braking systems have only added to the complexity and have increased the quantity of lines that can rust through on your car or truck. This month alone I have worked on brake lines in a 1992 van, a 2000 jeep, a 1973 MGB and a 1995 Monte Carlo.
Finding the leak is usually not too difficult if you can see the fluid on your driveway if not then place some pieces of cardboard under the car overnight. Press the brakes once or twice before retiring to bed. Come back in the morning and look under the car at the cardboard and start tracing the leaks from there. The worst areas I have seen are usually around the exhaust and under the engine. The heat seems to accelerate the rate of corrosion if the lines are in a place where they can get wet on a frequent basis.
Running a car on the beach near salt water can destroy these fragile metal lines in no time. So be cautious if you ever venture to the ocean. Even if you wash the undercarriage there may still be salt attacking the metal in hidden locations. Here in northeast Ohio the roads are covered with salt in the winter and this accelerates the rate of corrosion on our brake lines.
Now that you see the leak what can be done? Many times you will get lucky and the line has a threaded end near the leak that can be unscrewed so that you can install a new line in a similar length. The auto parts store has pre-made lengths that will already have the male threaded ends and the flares built into them. These are much easier than trying to make your own custom lengths.
There are a number of different standard sizes so beware that the rusted line may look larger than the replacement. You can tell which size you have by looking at the fittings at the tube ends. You will want to know the line size before starting so that spare parts can be purchased ahead of time. The parts counter can look up your make and model and will have a picture of your brake lines with the required sizes. You should be able to use a tape measure to rough out how many feet or inches of brake line you will need. Once you figure that out you are doing great.
If you are adventurous and handy you can get a flaring tool kit and with that you can make your own custom tubes using raw tubing that comes in straight lengths or on short rolls. The flaring tool is easy to use but it takes some practice to get the hang of making perfect flares every time. I will usually find the closest fittings to the leak and replace the line from fitting to fitting. There is a way to use a coupler to join two straight cut ends of tubing together but I do not recommend this on newer systems due to the much higher pressures that the ABS can put on a braking system. The exception to this would be rear brakes, especially drum brakes since these operate at a much lower pressure which these compression couplers can handle.
Now spray the threaded fittings that you wish to remove with a penetrating oil of some kind. Be prepared to use a light duty propane torch to heat these threaded fittings a little in order to break them free. There are special box wrenches called line wrenches that have a slot for going over the tube and they grip these fittings better than standard wrenches so they do not get stripped. Do not be surprised if the nearest removable fitting is many feet away from the leak, it is much simpler to replace that entire line than it is to deal with the same line springing leaks later on.
There are a few ways to cut the old lines depending if you are planning to reuse them or not. To reuse any lines by flaring them or making a compression coupling up for them you will want to make a clean cut using a small tubing cutter which is specifically designed for this duty. If you are just chopping the old out in order to make way for new lines from end to end you may be able to wedge a hacksaw in there to cut away the lines. The fastest and simplest method is to use an abrasive cut off wheel on an air motor. this will give a clean cut that may only require a quick rounding off of the edges with a flat file if you are reusing that piece of tubing.
Once you have removed the old rusty line you need to clean up the area where you will be putting in the new line. It is important to have any grime and dirt removed and do not allow the lines to make contact with the car or other lines. To keep the lines from rubbing against other things you can put rubber tubing like fuel line over the lines then use the zip strips to pull the rubber shield tight to the brake line. If the line you installed does rub somewhere then you will need to gently bend it out of the way.
Now that the line is replaced it is time to flood the line with brake fluid. You need to make sure to use the recommended brake fluid for that particular car. DOT 3 covers most of the vehicles I work on. The simple way to fill the line is to open the fluid reservoir cover and then loosen the farthest fitting from the master cylinder. Once you see fluid flowing out of that fitting close that fitting. Repeat for any other lines you replaced. Next find the nearest brake bleeder screw and get the correct line wrench on it.
Next spray penetrating oil on the fitting and get the torch ready just in case. Then with a helper at the pedal and the engine off the wrench person open the bleeder about 1/4 turn, hold it open and have the pedal person press pedal slowly to the floor over a count of three or four. As the pedal stroke ends close the bleeder screw. Tell brake pedal person to let up and wait for your signal to go again. Open the bleeder a quarter turn and have the pedal pressed slowly closing the bleeder before the pedal is all the way down.
Repeat until no air is seen coming out of the bleeder. Keep filling the reservoir s that you do not run it dry. Work on the line that is the farthest from the master cylinder first and work your way back to the master cylinder. I usually start with the passenger rear then driver rear passenger front then driver front. Do not turn on the engine until the air is out of all of the lines.
ABS systems can be worked on in this way as well but it is imperative that you do not start the engine since this may throw a warning light on that you cannot easily reset without access to the $4K electronic ABS brake test tool. If you cause any problems that cannot be solved easily you can try disconnecting the battery from the car overnight as this may reset some older ABS systems.
If you are afraid to try this job at least you will be able to tell your mechanic where and what the trouble is so that he or she may be able to give you a more accurate quote for repairs.