Hey guys,
I bought a little 120y wagon it had a rooted master cylinder in it ,pedal flat to the floor,replaced with a brand new one yesterday and tonight after work i bleed the system.
Well it does have a little stopping effort but the pedal is still pretty much on the floor.
The wheel cylinders appear to be good so are the pads and shoes this has reall pissed me off.
The only thing i doubt is the break booster how do i test if this is stuffed

Any idea will be appreciated
Cheers Anthony

Ok,
Assuming the wheel cylinders are ok as you stated:

- Check the one way valve on the vacuum line is facing the correct way between the booster and the vacuum pickup.
They normally have an arrow which points away from the booster.
- With the engine off, press the brake pedal a few times to bleed off any residual vacuum. Hold down the brake pedal. Start the engine. Pedal should drop slightly.

Also,
- Did you bleed the new master cylinder?
- What is your method for bleeding brakes?

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Rod

a shaged break booster wont make the pedal go to the flore nore will the valve but as said by rod how did you bleed the systom because it sounds like it has air in it

Ok my method was first i bleed the back breaks, i started by pouring fluid into the back reservoir then a helper press the pedal a cpl of times held the pedal down, i then opened the nipple under that reserviour until the fluid came out into the jar with no bubbles.
Then i went to the furthest wheel cyclinder pass rear and with the same method bleed through then onto the drivers rear,
The front reservoir same method of bleeding then pass front then drivers front, re did the system twice adjusted the rear shoes and it's still sh*t house, I haven't checked the 1 way valve as i didnt remove it.
I have double checked for leaks cant find anything i have about 1 to 1 2/2" of effective break before she bottoms on the floor very similar to before i replaced it!

tell me what im doing wrong or the best method of doing it.

Cheers Anthony

that is the right method as long as your helper isnt pushing the pedal to the flore or lifting it before you lock the nipple. thairs not that much to it if thair is no leak and is bleed right it will work. as i said before the booster dose not afect pedal travel nore dose the booster valve

[quote="old-tin"]that is the right method as long as your helper isnt pushing the pedal to the flore

Im a little lost here my helper has been pushing the pedal to the floor then i will do up the nipple call out pedal up...pump it a cpl of time's hold to the floor then i would bleed the nipple and again...and so on...
when you place your foot on the pedal you can't turn the tyre but the pedal hight is sh*t and it bottoms out when you want to apply more break pressure

Cheers Anthony

I use to bleed my brakes that way,but i find you can be airrating the fluid if pumped up to build pressure well theres air there.
i prefer to blow all the air lines out clean then just leave the nipples open ,pour the fluid in then was til theres no more air comming out.takes about 5 mins. this works fine most of the time but sometimes you just have to help it with a slow pump of the pedal.

your booster is only there to make the pedal easier,when its stuffed it a lot harder to push the brakes down and leans your motor out.

_________________
68 510 - soon to be restored into a replica 68sss
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GET THAT DATSUN DIFFERENCE!

Yeah she feel's flat dosen't really pump up so to speak, the pedal remains the same feel regradless if the engine is running stoped or pump it a cpl of times.
I bougt the new master from Abs in seaford vic and i showed them the old one. I confident it's the correct master it's exactly the same there must be something im over looking.

Murphy's law...yeah slapp it in bleed that all should be good

Cheers so far fella's Anthony

try adjusting the drum shoes out farther. air in the system only makes the pedal soft sounds like there is to much travel on the pads.
cheers bc

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Team AFRICA doing it because we love it not because we can afford it!

Cheers mate
yeah have already tried that. measured the diameter of the drum's there close to new size.Shoes are pretty good,
This is what has really done my head in ,I have done pretty much everything I can think of...?
Hand break is about 3-4 click's so she's about right

I'm going back to square 1 and starting over again.

Hey guys,
had an idea i have just bought the car i have no idea what the previous owner has or hasn't done im wondering if the length of the boster rod to pedal is out of adjustment and im only get a small amount of travel hence to the floor with a little break

Does anyone know the correct length ratio..?
Cheers Anthony

when your helper pumps the breaks have him aply a small amount of presher to the the pedal, crack the valve and have him push the pedal SLOWLY without pushing it to the flore or lifting it lock the valve and go to the next one. remember to start at the back ferthest away from the junktion block or you will just push sh*t up hill with a sharp stick.

yeah mate we bleed it again another 2 bottles of fluid,flushed the whole system again,tommorow I going to question ABS about the master Im thinking somethings wrong there perhaps they gave me a smaller master as the original was 3/4.
I have had "advice "that perhaps there still is a air lock somewhere but i can't see how with the amount of times we have bleed this bloody thing.

What i have noticed it does pump up at the end of the bleed but no where near 100%,start the car straight to the floor except for the last 1" -11/2" travel and wont pump up.
No fluid leaking anywhere joints ect wheels cylinders no weeping ect.
shoes have been adjusted hand break is roughly 3 clicks
master has been bled and all wheel and caliapers
Engine runs smooth and there is vacume to the booster.

F if i know
Cheers Anthony

Try adjusting the rear shoes so that you can't get the drum on (make sure that the shoes are perfectly centralised). Then loosen off the shoes a little at a time till you can just get the drum on. If it feels like it's dragging, then this is good. Then try bleeding the brakes again. Note that there doesn't need to be a big gap between the shoes and the drum. If this works then you can loosen the rear shoes off ever so slightly so that there very little or no drag on them, but not so that the drum just falls on and off easily.

Also, how are you adjusting the rear shoes. Are you using the handbrake adjustment, or the little square cam that sits between the pivot points at the top? this latter is the method for adjustment, and if it's not done right, then you'll never get good pedal feel.

Another thing - has the car got non standard brakes (calipers or wheel cyls)? If so, then the size could be out of whack.

As you said, also check the pushrod between the pedsl and booster, and booster to master cyl.

Another thing I've noticed in the past is if you have new or rebuilt calipers, the seals can pull the piston back away from the disc. You can overcome this by removing the caliper off the disc and pump the brakes until the piston returns into the right spot (ie in the neutral position the seal will hold the piston in the correct place). It's a bit like tightening suspension bushes with the car sitting at the correct height, if you follow.

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Get some line clamps and try clamping of different corners and see what the effect is on the pedal. This should help you figure out what is going on. I.E. if you clamp of both rear and the pedal comes up strong then you know there is an issue with the rear brakes be it pad clearance or air in calipers. Ive been having the same problem on my car have used about 12 bottles of brake fluid during bleeding and that is with recycling fluid once it was coming through clean But i have just rebuilt my front calipers so im going to try what warps said.

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