Frogman

Ok so i changed my master cylinder a week ago with zero issues, the pedal was rock solid, I finished replacing the drum breaks AND the cylinders, the pedal was spongy ( obviously). While bleeding the rear cylinder the reservoir went empty on the side close to me ( for whatever reason that side drained faster every time) and I refilled it until I got fewer bubbles, I press the pedal ( after tightening the bleeder valve) and the pedal goes straight to the floor. WTF is going on, I already checked, zero leaks.

GSLSEforme

Are you gravity bleeding or having someone pumping the pedal and holding while you open bleeder. You still have air in the system.If only doing the former,recommend you do the latter. Proper adjustment of rear brakes also crucial to a good pedal.

mazdaverx713b

iTrader: (91)

I agree with the above. Have someone help you bleed the brakes by operating the pedal while you operate the bleeder screws. Making sure the rear brakes are adjusted properly is crucial in that you will not get a good pedal feel if the brakes are not adjusted properly.

t_g_farrell

iTrader: (1)

Yep, rear drums not adjusted will result in a diminish pedal feel for sure. If you have to bleed by yourself you should either use a vacuum bleeder, a pressure bleeder or do what I do. I loop the bleeder hose up above the bleeder valve to approximately tire height. This loop once fluid starts going thru will prevent bubbles from getting sucked back in. You can pump a few times, check for new bubbles, check/fill reservoir, then pump some more until you feel its bled. Then close the bleeder and see how the pedal feels. If anyone doubts this works come check my brakes out.

Frogman

It can't be the adjustment because the drums have about a few degrees of turning before they scrape and / lock . I adjusted them each until the wheel spun without locking and held the adjuster in place while tightning . Il try the pressure method instead of the gravity method . I suspect the New cylinders had a lot of air in them / introduced air into the system . Plus I suspect the resi sucked New air in too when the side nearest to the driver emptied first.

Frogman

Ok did it by my self wit ha PVC pipe. I pumped the brakes twenty times the first time ( remember the brakes went straight to the floor) . jammed the pipe to hold the pedal down while I went to open the bleeder valve, a bunch of air and foam came out. Did it again, pedal started to get some " feeling" this time a lot of liquid + bubbles came out. did it eight more times until the pedal was rock solid. Closed the bleeder valve. Returned tonight and the pedal gets hard after 3 pumps but still has about an inch of play. Iv already quadruples checked for leaks, the booster was in the right place when I put the new master cylinder in. How much play should it have? Once again I spent over hours meticulously adjusting the drums last night I started with the drums locking to craping to no noise and tried to move as close to when the scraped as possible. I'm starting to regret not changing the brake lines and using the old ones .

GSLSEforme

1-2” of play at top of pedal is@right. Every car a bit different.
Having to pump pedal 3 x to get full pedal means you still have air in system. How far does pedal go down on1st pump after car sat for some time.
If using the pump and bleed method,it takes two people to do it correctly. If you can’t get a second person to help you,you need to choose a different method, perhaps renting the equipment to vacuum bleed from advance zone.

If you are certain rear brakes are assembled/adjusted right,no point in readjusting any more. A correct adjustment will not change.

When pumping brakes to bleed,3 SLOW pumps is all that’s necessary to build pressurize in system. Pumping longer does no more for building system pressure. If you pump too fast,you aerate fluid which foams it up and adds to air in system you’re trying to get out.
Pump and bleed method requires 2nd person to pump 3x and hold pressure on pedal while you loosen bleeder to release air and fluid. At point pedal stops travel to floor,you close bleeder and have pumper pump 3x again and repeat process.This requires communication between both of you,so as to not to inadvertently let any more air in.

Proper way to bleed brakes is to start with wheel of car furthest from master cylinder. RR-LR-RF-LF. Understood your car has only one brake bleeder on rear brakes. What you can do is tap the opposite wheel cylinder from bleeder lightly with screwdriver between bleeding to help dislodge air bubbles and then bleed again.
Bleeding @ 4x at each bleeder is sufficient to remove air at that location before moving on to next wheel. You should be bleeding all brakes in sequence even though you only recently worked on rear brakes.
It is normal for the height of brake pedal on a properly adjusted/bled system to drop slightly on starting car as vacuum builds and booster does its job. Also normal on properly adjusted/bled system for brake pedal to be slightly firmer on 2nd pump after sitting overnight or longer.

You mention regretting not changing brake lines on car. Hard lines are good if they don't leak fluid,you can visually follow lines from origin to end,if dry,they're good. They can't let air into system without leaking brake fluid out,same goes for flexible hose at each caliper and rear axle housing. The rubber does age and break down internally,symptoms of this can be pulling to one side under braking if one of the caliper hoses has a problem. Another symptom caused by same thing is dragging brake(s),inner layer of hose can delaminate and create a flap that closes hose off and holds residual brake pressure in that component after pedal released.
You should be replacing all rubber hose in system strictly due to its age for safety,they do degrade and external plies do crack,particularly front hoses as they twist back and forth on each turn of steering wheel. The hoses are not likely the source of soft pedal. You can check this by watching/putting your hand on hose(s) while a helper presses and releases brake pedal. You may be able to feel it move perceptively,but you should not see or feel it swell.

Have you driven the car after you bled system,how does it stop??How does pedal feel?

t_g_farrell

iTrader: (1)

Because the rear reservoir went dry when you started, you now have a lot of air in the system. Just keep bleeding. Sounds like you have the rears adjusted ok now. Using the PVC pipe works as long as you are careful. I used to have my wife pump the brakes before I switched methods. See if you can get a buddy or SO to do that for you.

chuyler1

iTrader: (1)

As mentioned above, rent a friend and park them in the driver's seat for 15 minutes.
You: "Pump"
Friend: "Done"
-- open bleeder just enough to let fluid flow out into attached tube --
Friend: "Floor"
-- close bleeder --
You: "Pump"
Friend: "Done"
-- repeat --

If you are dumping the fluid into a container the similar size as the master cylinder reservoir, plan to fill it half way for each wheel RR,RL,FR,FL and remember to top off the master cylinder reservoir before moving to the next wheel.

Frogman

Il get my dad to help me, I just have to take the wheel off again , not a big deal .

RCCAZ 1

iTrader: (10)

Went through the exact same exercise last month. Started with air compressor and speedbleeder. Worked with my son. We went totally around the car 4-6 times before we barely got pedal, then disconnected the speedbleeder and manually bled all 4 corners about 4 more times AGAIN before getting normal pedal feel. Went through a full quart of fluid during this exercise. Stick with it and be patient. It WILL happen.

Frogman

I went through a full quart too the first time , but air got in . This car has never had " firm " brakes . The thing is the master and breaks were shot and I replaced everything but the lines ( I have new one's I purchased ). I put New everything minus calipers / drums. The drums barley slid in so they can't possibly be over worn. And the caliper worked well when I tested them and shouldn't be replaced unluess they leak / don't compress afaik . I have read that this car is notoriously hard to bleed due to the single rear bleeder system . I would like to inform every one I did the pedal bleed on the REAR breaks only , I have never bled the front tires . Tomorrow my pops is going to help me and my plan is to pump the rears 3 times ( already did it my self eight times , went from pedal going to the floor to getting firm after 3 pumps and only having 1-2 inches of play ) and doing the front 2 times . I understand I won't ever get a " firm " pedal on a 40 year old car . I just hoped that replacing all the hardware would work and my master system DID work ! It was a little frustrating to instal but it worked .

GSLSEforme

When you get all air out of system with brakes adjusted properly you can have a normal firm pedal.
If after bleeding your pedal is low but firm consider replacing front calipers they may be bound up internally from crud that accumulates behind piston in bore and their seals hardened from age,both of which prevent piston to apply and retract fully- sometimes not enough for brakes to drag,but not enough to apply fully either and cause a low pedal.
If you replace calipers,do the flexible hoses at same time. Your brake hydraulic system wil be all new and you will have a high firm pedal and car will stop very well. The one bleeder in rear makes it a little harder to get air out but careful bleeding and some patience you will be successful.

craaaazzy

iTrader: (9)

Did u bench bleed the master?

another way to bleed by urself is to put ur hose in a bottle with a bit of clean brake fluid so hose is submerged. That way, it will suck clean fluid and not air back in the system. Have done this countless times as I hate asking for help.