Master cylinder or air in the line

BY brake fade away I take it that you mean the pedal goes to the floor after you taken your foot off the brakes. . The valve you left out is a compensator valve that proportions the pressure between front and back to stop rear brake lock up and side skidding. I think the problem is in the master cyl in that the nonreturn valve under the second piston is not working and hold residiual pressure in the rear lines (Assuming they are drum brakes). If not you will need to bleed the m/cyl by cracking the lines at it one ata time and emptying the cylinder of trapped air allowing a full charge of fluid every time you pump the brakes.

Sounds like you may have a hydraulic leak somewhere. Check the rear wheel cylinders and front brake hoses going to the calipers.

fill master cylinder, start at right rear. the way I do it is make sure cap is back on master cylinder. pump the brakes a few times then hold them. have another person open the bleeder valve at the tires until brakes go to floor. hold them down until bleeder is retightened but be sure master cylinder is not out of fluid. then go to left rear and do the same procedure, then right front, then left front. check fluid and if air is all out there should be brakes. good-day ! THIS IS HOW I HAVE ALWAYS DONE IT ! heres a little trick of sorts. you can change a master cylinder, and if you bench bleed it first. and no fluid is lost from the master cylinder lines you do not need to bleed the whole system. but make sure cylinder is full of fluid before putting on vehicle and all air is out of master cylinder.

Sounds like it still has some air in the system or a bad master cylinder. First try bleeding all air, there is definitely some air left in the lines and this is most probably causing the problem. Bled the lines at the bleeder screws on the calipers. ---------- There is air left in the brake line.Any time the brake system is opened to replace brake lines, caliper, pads etc etc.Mostly the air enters the system, and that air has to be completely bleed.Otherwise the same symptoms , what you are getting will be noticed.-------- Brakes can be bled manually, with a power bleeder, injector tool or vacuum bleeder.IIt does not make any difference which method you use as long as all the lines and components are flushed with enough fluid to remove any trapped air bubbles or air pockets.----
The most common bleeding procedure is to bleed the brake furthest from the master cylinder first, then bleed the other brake that shares the same hydraulic circuit (which may be the other rear brake on a rear-wheel drive car or truck, or the opposite front brake on a front-wheel drive car or minivan). After these have been bled, you then bleed the other brake circuit starting with the furthest brake from the master cylinder.--------- When the complete air is bleed from the line, the brake should be firm when car is on.In your case brake brake pedal is loose and goes almost to the floor when car is ON.This is due to Air in the line.Get the complete air bleed from brake line.------- This will help.Thanks.Helpmech

Hi,
Probably air in the brake system. Bleed your brakes thoroughly. Start with right rear, then left rear, then right front then left front. Maintain proper fluid level in master cylinder while bleeding. Brake pedal hieght comes from the rear brakes, as those are the longest brake lines in the system. Mike

Did you remember to bleed the master cylinder itself? When the master cylinder runs dry you should start bleeding your brake system at the master cylinder and then continue on to each of the four wheel cylinders.

the master cyclinder is divided into diagonal wheels. meaning that each line from the master cyclinder provides fluid to a front wheel and rear wheel. on the front resevoir of the master cyclinder it would be perhaps the left front and right rear brake for example. you need to block the lines going to the rear wheels independently and then bleed the brakes again starting with the wheel furthest from the master cyclinder.

Start with brake in the rear that is the farthest away from the master cylinder ( if your master cylinder is on drivers side start with passenger rear,pump up brake pedal until hard have someone else open bleeder valve until air or fluid squirts out,while holding brake pressure even if goes to the floor dont release pedal until bleeder valve is tightened or you will **** air back into the line,do this several times making sure you get a full stream of brake fluid and no air,continue to other rear wheel and then proceed to front wheel furthest from master cylinderand then final wheel. if you still don't have brakes change master cylinder and bleed all brakes again.

Check the fluid level in mastercylinder first. Inspect brake lines for any leak. Also it could be a leaking caliper piston on the front brakes or a wheel cylinder on the rear. Will have to remove the tires on front to inspect and if you do not have rotors on rear you will have to remove the brake drums to inspect for a leaking wheel cylinder. Hope this will help you.

Its not air leak, you must bleed air from system. You have to bench bleed the master cylinder, then bleed each caliper starting from the right rear, then left rear, then front right, then front left. If you've already done this, then do it again, you must have air in your lines or they would work. The only other thing could be your rubber lines are bad and swelling(absorbing the hydraulic pressure) but they would have to both be completely mush.