Syphon it out and refill the MC then start bleeding and refilling it till the old one clears out-
June, 17, 2011 AT 8:32 AM
Easiest way is to open the bleeder screws at each wheel, loosen the cap on the master cylinder reservoir, and let it gravity bleed. Let the old fluid run out of the reservoir first so you don't just dilute it, then when the level gets real low, fill the reservoir and let it continue bleeding. When you see clear fluid coming out of one of the bleeder screws, tighten that one and wait for the others to do the same. Don't let the reservoir run completely empty because air will be drawn in and cause a mushy pedal.
When you're done, do not fill the reservoir. See how full it is before you start bleeding and fill it to the same level. If the fluid was somewhat low when you started, the front brake pads are worn. When new ones are installed in the future, the fluid level in the reservoir will be higher. By not filling it to the top now, you leave room for that fluid to go when the new brake pads are installed.
You can speed up the bleeding process by having a helper press the brake pedal, but just do one wheel at a time and close the bleeder screw just before he releases the pedal to prevent air from being drawn in. It is also real important to never push the pedal more than half way to the floor. Doing that runs the lip seals over the crud and corrosion that builds up in the area where they don't normally travel and can rip them. That will result in a slowly sinking pedal when it is applied.
Be absolutely certain not a hint of petroleum product gets into the brake fluid. That includes engine oil, transmission fluid, and power steering fluid.
June, 17, 2011 AT 9:53 AM
I have a bit of an opinion on this. I do a lot of brake flushing and I would strongly advise NOT to let the system run dry in the process. That will introduce air into the system that may be very hard to get back out. Many vehicle use ABS systems that require a scan tool to get them bled out once air is introduced. The best way is to suck as much of the old fluid out of the reservoir before starting and refill it with fresh fluid before starting to bleed at the wheels. Bleed each wheel until the fluid flows clean without ever letting the master go dry.
June, 17, 2011 AT 11:16 AM
Amen! Brother that is exactly what I'm trying to say but in short terms-lol I tried the scantool on a 1991 GMC S-15 Jimmy with the valve depressor. You know me Wrench I love to play short cut and take my sweet time but when my integrity is questioned I bite back hard and to the point-lol -Bye Guys see you all later, Have a good one