You should bleed your brakes and refresh the fluid every two years, more often if you track you car. Brake fluid is hydroscopic, meaning it adsorbs water just sitting there and with minor use. The fluid becomes more corrosive over time and can lead to poor performance or just failed sticky brake calipers.
I rate this a 2 out of 5 bloody knuckles. You need some not-so-common tools and well.....you're dealing with brakes.
1.5hrs Total with wheel removal/installation.
Proceed at your own risk:
You're dealing with brake fluid which can wreck paint, plastic, and your eyeballs.
The most common mistake is OVER-tightening the bleeders which strips them out. The fix is a new caliper.
The next most common mistake is running the master reservoir dry.......which can be a pain to completely bleed the system.
What you Need:
Jacks, lug nut wrench, torque wrench, for removing and reinstalling wheels.
Metric box wrenches for the bleeders.
DOT 4 Brake Fluid (Porsche or other high quality)
Catch can and tube
What I'd recommend you get:
(2nd Option) Vacuum bleeder
Magnetic large catch bottle
Rubbing alcohol for mistakes.
Start by jacking up your vehicle and removing the wheels. There's other threads on this.
You CAN bleed the brakes without removing the wheels, but it will make it much more difficult..... and you'll likely scratch your wheels trying to loosen the brake bleeder. Just pull them all off. You can do one by one....but again, more difficult.
Good time is when you're swapping to winter wheels.
Take Note of the Reservoir Level
Next get your power or vacuum bleeder and verify the cap fits the reservoir.
There's two ways to use a power bleeder. You can fill it with brake fluid, which when pressurized constantly replenishes the master reservoir. Meaning you never run the risk of pushing air into the brake system. This is the fastest method as well. Since you just go around opening bleeders and flushing the system.
The downside, is if you have a leak, you get brake fluid everywhere. If you forget and open the system at the cap, brake fluid everywhere. It also trashes the brake bleeder unless you thoroughly clean it with rubbing alcohol.
The 2nd way is just to use it as a pressure vessel. You have to carefully watch the master reservoir to make sure it doesn't go empty. It takes more time, more refills, more stop/starts, but it eliminates a potentially messy mistake.
You'll also need brake fluid. Get the large container, and get two of them. Remember, you're not just bleeding but flushing the system and you don't want to run out. I did it with one of the standard Porsche cans, but barely.
Next you will need a catch bottle, tube, and box end wrench. This one was relatively cheap and worked like a charm. I'd highly recommend these two tools for your toolbox. Fit the wrench, remember lefty-loosen, then add the tube. You're going to have to unscrew the bleeder about 120 degrees for good flow, don't need much more than that. NOT YET. A good trick is to start the wrench at the farthest clockwise it will fit. That's a good point to STOP tightening the bleeder when done.
(Picture is with bleeder OPEN)
Nows the point to start bleeding. Either fill the pressure bleeder with fluid or just connect it dry to the reservoir. Pressurize it to no more than 10psi and check for leaks (if you filled it). You can then move to one of your brake calipers and start bleeding. The fronts have an inner and outer. Start at the inner to flush, then the outer to final bleed/flush. The rears have a single bleeder.
Be sure to always have pressure on the system (power bleeder) or vacuum (vacuum bleeder) before opening the bleeder. Always close the bleeder first before relieving pressure. This keeps air /dirt out of the system.
Starting at the right rear (longest run), flush the system until you see fresh fluid / refill the reservoir 2 times / or bleed a 1/2 bottle of fluid. Maintain pressure in the power bleeder above 5 psi and don't let the master reservoir drop too much below the bottle split line. It gets hard to see below that and easy to go too low.
Move to another caliper and repeat. The goal is to keep flushing until you see fresh (clear-ish) fluid at each one. This roughly takes the entire bottle of Porsche brake fluid by the time you get all 4 corners. Repeat the 1st caliper you did again at the end, checking for fluid color and any air.
When complete, make sure all bleeders are tight and caps are replaced.
Fill the reservoir to level when you started. This keeps it from overflowing if you back the calipers off during a brake change (and forget to suck some out of the reservoir).
BEFORE reinstalling the wheels, pump the brake pedal until it is ROCK HARD. It should take 1, maybe 2 pumps to use up the vacuum assist and verify you have good pedal feel. If it feels spongy no matter how many time you pump it, you have air in the system and need to bleed each caliper again (inner/outer in fronts). Check for air bubbles.
Reinstall wheels, check brakes again, take it for a test drive checking brakes at low speed.