How do you bleed brakes after changing the master cylinder for a 1991 explorer?

Answer 1

Hopefully you bench bled the master before installing. This is done by putting the master in a vise and using a screwdriver to push the piston in slowly & fully several times until the air is out of the master. Use a bleeder kit (comes with some masters) or put your fingers over the side holes and let the fluid come out when you push the piston in and don't let air back in when the piston is released. After doing this install the master in the truck and tighten all the lines. Make sure the master is full and loosen the lines going to it slightly to the point where fluid is seeping from them. Have someone get in the truck and push the pedal down very slowly till it bottoms out. Hold the pedal down and tighten all the lines. Release the pedal slowly. Loosen the lines again slightly and have the pedal pushed down & held again till you tighten the lines. Do this a few times till you think the air is out and the tighten the lines to the master. If you're lucky you won't have to bleed it at the wheels (pedal will be fine). If the pedal is mushy you will have to open all the bleeder screws at the wheels (without breaking them) and let it gravity bleed (let it drip). At no times can the master run dry or you will be doing this all over again. Once you have let a bit of fluid out of each wheel tighten all the bleeder screws. Make sure master is full! Pump the pedal 3-4 times and open right rear bleeder and have someone push down the brake pedal & hold it till you get the bleeder tightened. Try to use a 6 point wrench to open & close the bleeder so you can watch & see if air bubbles are coming out. Do this 5-6 times or until no more air comes out. Then do the left rear then right front then drivers front last. all the air should be out by then.