A little background before I begin because I'm sure that this will cause a stir and that's not my intent. I used to teach braking systems and ABS diagnosis for 4 years. There is a lot of different consensus on how to bleed brakes-pump and hold, vacuum, reverse bleeding, power bleeding. None of them I have read are incorrect however, there is possibility of causing other problems with the system by doing it some of these different ways. Most people don't have a power bleeder at home and with the newer ABS systems, these are not the best method anyway. Besides, usually power bleeders are filled with brake fluid that can be months old and most likely already contaminated and "wet". Vacuum bleeding is an excellent way, but again, most people don't own or have access to a good vacuum machine. A Mityvac is NOT a good vacuum machine although if you are competent with it, you can do vacuum bleeding, but it's not necessary to even use it in this method.
Working on brakes should not be attempted unless you feel that you are competent in understanding the following instructions.
We've all been taught the "Pump it up, Hold it, Tell me when it's on the floor, OK, Pump it up again, Hold it again, tell me when it's on the floor", etc. method, and while this does, in fact, work for bleeding the system, it can cause problems that are not immediately apparent. This method pushes your master cylinder into zones that it's not used to being and can cause issues with the seals and cups inside because of corrosion and wear. Sooner or later down the road, and it doesn't always happen, but your master cylinder can fail from grit and corrosion that was loosened when you did your bleed. At that point, you are purchasing an expensive piece, having to do the labor, and then having to do the whole damn thing all over again.
So with that being said, here is the best way to bleed your brakes:
When bleeding your brakes, remember this: Gravity is your friend, unlike around our waistlines (I can attest to THAT fact unfortunately). It's very simple to bleed your brakes, remove the air, and never invade your master cylinder where it shouldn't be invaded.
I have taught this method for over 30 years and have never had a single issue with a system that is in good working order. If there are problems with your vehicle in the ABS controller, proportioning valve, lines, or calipers, then the vehicle needs to be repaired before attempting this method. This will NOT make up for worn parts such as pads, rotors, calipers, master cylinder, booster, etc.
Gravity bleeding is easily done by a single person, but the only downside is that it takes a bit longer to do and you MUST pay attention to your master cylinder and fluid level. Here's how:
Clean the outside of your master cylinder thoroughly around the cap area to make sure no dirt can enter when you remove the cap. Open your master cylinder and remove as much old fluid as you can from the reservoir. Remove the floating screen (if it's a Subaru) so you can reach all the way inside. I use a turkey baster that I have mounted/glued a piece of curved brake line in the tip so I can reach around through the side slots and get as much fluid out of the bottom reservoir as possible. Make sure you have wet rags around in case you spill some fluid when you are sucking it out. Wipe any spilled fluid up immediately with a wet rag and rinse the rag. Once you have it as empty as possible, fill it with the new fluid of your choice and reinstall the cap. ONLY use a NEW bottle-never one that's been sitting around half full, even if it's only a few months old, and put the cap back on between fills of the master cylinder. Make sure you have enough NEW fluid to completely flush your system-a 32 oz. bottle/can is a good size.
NEVER USE DOT 5 SILICONE FLUID-IT IS NOT TO BE USED FOR ABS SYSTEMS. (If you have questions about this, PM me and I'll explain exactly why it doesn't work.)
Jack up the car at all 4 corners and place it on stands (if you have a hoist, even easier). Remove the wheels and break loose each of the bleeder screws and then check them to make sure that they are open and not rusted shut. If they are, use a piece of wire or drill bit to open the center and side holes and then reinsert back into your calipers or wheel cylinders.
If you have bleeders that you think are going to break off, there are several methods you can use to loosen them. If you have access to an oxy/acetylene (cutting/welding, not a propane) torch, you can heat the caliper JUST right around the screw, red, not flowing metal red, but just red, and quench them with water. (DO NOT DO THIS WITH ALUMINUM CALIPERS). This will make them come loose easily. If you don't have a torch, soak them in PB for a day before you try to remove them. Find a socket that fits the bleeder but doesn't bottom all the way to the caliper. Put the socket on the screw over the nipple and tap the flat end of the socket lightly several times with a hammer (NOT A BFH-a small hammer) and then try to loosen it. It may take several times of trying and tapping, but be patient. This helps the PB penetrate and also loosens the threads with the shock. (You CAN do THIS with aluminum calipers). Once you have them loose, see above about making sure they are open.
Find some clear hose that will fit snugly on the nipple of the bleeder screw long enough to reach from the bleeder down into a container on the floor. Go-kart/atv/dirt bike fuel hose works perfectly. Put the hose over the bleeder screw nipple and place the open end into the container (clear container with graduations it is IDEAL so you can see how much fluid is coming through-a Ratio-Rite cup is perfect) and open the bleeder screw taking care to make sure that the hose stays pointed in the cup. It will take a minute but you will see fluid building up above the bleeder in the hose (only on the rear as the bleeder screws point straight up-the fronts flow quickly without a buildup in the hose) and then it will start to drip into the container. Remove the master cylinder cap and "LET 'ER DRIP" for a while-usually 10 minutes is a good number to use as a beginning but it may take as long as 15. You MUST maintain a constant vigil at your master cylinder to keep it full as it will slowly go down. DO NOT LET IT GET DOWN TO EVEN HALF FULL-JUST PAY ATTENTION AND KEEP THE DAMN THING FULL...LOL.
Keep adding the fluid and once you see about 6 oz. in the clear container, then close the bleeder and move to the left rear. Refill the master cylinder and do exactly the same thing and look for about 6 oz. Move to the right front-6 oz., and the left front-6 oz.
Use just clean water to clean up any mess that you may have made and use a wet rag to wipe down the calipers to make sure that there is no fluid that leaked onto the paint (if they are painted). Put your floating screen back inside of the master cylinder, refill a final time, and install your master cylinder cap.
Make SURE to install the master cylinder cap before completing the next step.
Leave the car on the stands and start it and gently push your brake pedal several times. You'll find that the pedal is engaged sooner and firmer.
In approximately an hour, this method will completely flush your entire system and replace all of the fluid with new. Reinstall the wheels, lower the car, check the lug nuts for torque, and then test drive the car. Check the master cylinder a final time after your test drive.
Enjoy ! ! !