I bought a new Master, the mechanic bleed it and they said to me that it was the Kit that was damaged, but it continues the problem, the brake still touches with the floor. Now they say to me that it is the sensor of brakes abs.
Thank I need an advive.
Chevrolet Blazer 1996.
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First of all, I hope you got a new master cylinder with your disc brake kit. A new master cylinder should be bled before connecting the brake lines and then never allowed to pull in air during the rest of the bleeding process. A couple of fittings ans hoses should have come with the new master cylinder [see the kit listed for a picture]. If the master cylinder has an air bubble, you won't be able to properly bleed the rest of the system.
For the rest of the system you can make up a small catch bottle like the one pictured in the one man brake bleed kit; make sure the hose goes tot he bottom of the catch bottle. You have to cap the master cylinder reservoir before pumping the brakes or fluid will squirt out and all over; brake fluid is a like paint remover. Then start with the brake farthest from the master cylinder and bleed fluid out by having a buddy pump the brakes while you hold the catch bottle above the bleeder port so no air gets back in. [hint, put some pipe teflon tape on the outer threads only, not the inner end of the bleeder screws to seal the threads]. Check the master cylinder level often! If the brakes still are spongy after the first round of bleeding, have a buddy pump up the brake pedal with the bleeder screw closed and hold pressure on the pedal; you then open the bleed port until the pedal goes to the floor; have your buddy hold down the pedal until you close the port. Repeat on all brakes until the pedal is firm.
Did you get a good bleed with fluid coming out at all four wheels? If they bled good, and the pedal still goes to the floor, you need to check the brake master cylinder-it is probably shot with an internal leak. An internal leak will not let fluid pressure build up, so no brakes.
Did you keep the brake fluid reservoir from going dry while bleeding? If it went real low, air might have got back into the lines.
It is not uncommon when bleeding brakes on an older vehicle for the master cylinder to suddenly develop an internal leak and require replacement . Here's why: pushing the pedal all the way to the floor causes the master's piston to push in farther than ever before. The rubber cups then travel over a section of the cylinder not usually touched by the cups-old fluid can develop a crud there and when the piston pushes over it, the cups can get ruined. To avoid this when bleeding brakes, put a short piece of 2X4 wood block under the pedal. Then the pedal will not extend the master's piston beyond it's normal travel. Of course on a new master cylinder, you do not have to do this. A new master cylinder does require bench bleeding before installing, however, to ensure no air pockets develop from there.
Still air in system, sounds like the master cylinder has ran dry during the bleeding process, pumping more air into system. The lines running to the rear brakes are long, so you must bleed the fluid out the bleed screw in the rear 10+ times each side. Bleed, bleed, and bleed some more, keep bleeding untill that pedal feels good.
Your description sounds like you either have a leak or a damaged master cylinder. If you determine the m/c, BENCH bleed it before installing. Auto parts stores sell an inexpensive kit to assist in m/c bleeding.
My bet is failed master cylinder.
Did you bleed master cylinder before you installed it? If not you will never bleed air out. Bleed kit should have come with it. If you done this need to bleed wheel farthest from master cylinder first and so on.
Did you bench bleed the master cyl. before installing it? then when you installed the new master, did you bleed all 4 points? If yes, then check all for points for leaking caliper/s and leaking wheel cylinder/s. If the van has ABS, check the valve body for a bleeder screw and see if air bleeds out of it. If you've checked everything twice and did everything right then your new master cyl. may be defective.