For a car that is mainly used for daily driving, bleeding your brakes is not as essential - it can be done once every 2 years and it might not worth the trouble to learn all this.
However, when racing your car, it is recommended to bleed your brakes after each racing day. Sometimes, depending on the brake fluid used and your brake setup, you might need to do it at the track as well.
Mainly because of 3 reasons:
Bleeding your brakes is not that hard. It might take a little bit of time and the help of another person, but the process is very simple and quite straight forward.
Obviously, the car needs to be lifted and depending on your setup, wheels must be removed as well.
If you have only 2 jack stands, lift your car from the back first and then move to the front.
Make sure that the hand brake is off and block the wheels with a piece of wood / rock.
Remove the cap from the brake fluid reservoir and make sure that the reservoir is full.
Place the cap on top of the reservoir but do not tighten it. We only cover the reservoir to make sure no debris will get inside it.
Remove the cap from the empty bottle of water and drill a hole trough it - big enough for the rubber tube to go through. Place the cap back on the bottle and make sure the bottle is completely dry and clean!
I usually start at the furthest corner/wheel from the reservoir and place the end of the clear tube over the nipple from the bleeding screw located on the piston. Place the other end inside the bottle all the way to the end.
Ask your friend to pump the brakes about 10 times and at the last push to keep his foot firmly on.
Open the bleeding screw to let the fluid come out and then close it back.
Look and see if you notice any kind of air bubbles.
Repeat this until no bubbles are present in the fluid anymore. Even if no bubbles are present from the beginning, I still repeat this step at least 3 times.
During this process, while the bleeding screw is closed, double check the levels of the brake fluid reservoir and make sure is always full.
When opening the bleeding screw, make sure your friend is pushing on the brake pedal all the way to the end and that they will NOT lift the foot until you close the bleeding screw!!!
If they lift the foot before you close the screw, air will be sucked inside and you have to do to it all over again.
As an additional note, a lot of people are saying that when pressing the pedal all the way you risk the chance of tearing your master cylinder seals.
This might happen because in time there are sediments that are building inside the master cylinder and when pushed all the way, the seals could get damaged.
For a well, regularly maintained car, I hardly see how sediments will build up inside the MC ... but if you have your doubts, then have your helper press it only half way and make sure they do not move their leg up and stays half way until you close the screw bleeder.
A simple way to ensure the brake pedal will not travel all the way down is to add a piece of wood under the brake pedal.
Personally, I have never had a problem with this, but be warned and do what you think is best for you ...
Do the same for all the other corners, moving from the furthest corner to the closest corner to the brake fluid reservoir.
Speaking of the order, this is something that I prefer and used without a problem for quite some time.
When it comes to the "proper order" of bleeding the corners, personally I think that it doesn't really matter as long you bleed all corners properly and the fluid is clean. Again, this is me saying that so don't take it for granted. And this is because I haven't yet encountered a sound explanation as to why car companies requires a specific order (and usually is different from company to company).
If you have a sound explanation as to why, please do let me know. In any case, you can always consult your car's manual for the "proper order" of bleeding and follow that.
Once you are done make sure the reservoir is full, tighten the cap, press the brake pedal a couple of times and then go out for a test drive.
If everything was done properly, you should notice an improvement in the brake feel.
If by any chance the brakes feel soft and the pedal goes all the way to the floor, make sure all the bleeding screws are properly torqued, check the level inside the brake fluid reservoir making sure is full and if necessary repeat the bleeding process.
If you still have the same problem, then most probably the master cylinder is damaged or you have a leak somewhere. In that case I strongly advise you to take it to your preferred shop and let the mechanic double check everything.
If you plan to change the brake fluid you are using to a better one, you must completely remove the old fluid.
Have a small bottle connected to each of the bleeder screws and pump the brakes until nothing comes out on any of the corners and then leave it to sit for a couple of minutes. Because the system is empty, it will take longer to make sure you have removed all the bubbles. Take your time and have some small brakes here and there where your friend can take his breath for a little :). Pumping those brakes is not as easy at it might sound ... is a true workout.
Dispose of the remaining fluid in a proper way - brake fluid is very harmful to nature.
Take the bottles to your mechanic or your local shop and ask if they can dispose of it.
In the "What do you need!?" section of this DIY I make reference to the fact that you can bleed the brakes by yourself if you purchase some kits. If you are interested, do a search for the following items and you can purchase them:
Pay attention to spills - brake fluid can melt/damage your paint. Try and wipe it down and clean the area asap if there are any kind of spills.