Procedure for flushing brake systems and replacing brake fluid:
DO NOT USE ANY SOLVENTS TO FLUSH BRAKE SYSTEMS. USE ONLY FRESH BRAKE FLUID FROM PREVIOUSLY UNOPENED CONTAINERS. (If the forum software offered any additional ways to emphasize this, I'd have used them as well.)
There is simply too much risk of all types of solvents contaminating the brake fluid and causing premature seal failure.
Make sure you have ample brake fluid before starting. A quart bottle is minimum and may not be sufficient. Ask if you can return unopened bottles before purchasing. If they say, "no," find a different parts store ... the staff (and management) at this store are uninformed, untrustworthy idiots.
Factory sealed bottles of brake fluid have a long shelf life. Once the metal and plastic seal under the cap is broken, atmospheric humidity begins contaminating the brake fluid. (Even in subzero low humidity conditions.)
There's a decades old ongoing discussion regarding the shelf life of an opened bottle of brake fluid. I dispose of opened bottles rather than risk using contaminated brake fluid.
I usually buy brake fluid only in the smallest available bottles, by the case. Opening many small bottles while flushing brakes adds tedium so I start with a quart bottle. I often have a second quart bottle on standby but only open it if I'm fairly sure I'll use most or all of it. Otherwise, I switch to the smaller bottles when I've used all the first quart.
With one exception, the basic procedure is identical to bleeding brakes.
The exception is, instead of stopping when you have firm pedal 'feel,' you continue until you can plainly see clear, clean brake fluid flowing from each bleed valve.
Tools and fixtures for maintaining system pressure while bleeding brakes are especially helpful when flushing the brake system. However, it can be done with coordinated help of another person. (A third person is helpful, to continuously keep the master cylinder topped off.)
The goal is to use the new fluid to push the old fluid out of the system. Any pauses in the process creates a risk the old fluid mixing with the new fluid. A pause for a quick sip of coffee or soda is okay. Likewise, moving from doing one wheel to the next is okay. Pausing for a cigarette break is too long. (Bathroom breaks are also too long but sometimes absolutely necessary ... my wife helps me with bleeding brakes but I find someone else for flushing brakes.)
A brief break between flushing the front brakes and rear brakes is acceptable. It may be necessary to relieve biological pressure, un-kink leg and back muscles, or grab a quick sandwich. (If your truck has separate brake boosters and slave cylinders, make sure you flush the one for the front brakes before taking this break.)
Obviously, flushing brakes is a lengthy process, especially if you're using the two (or three) person approach. So, schedule ample time for the task.
