brake problem
 

got the new master cylinder on and bled. all the lines are air free and have fresh fluid in them.

here is the problem i'm having. the first half of the pedal travel is nice and firm, after that, the pedal is a lot softer and the brakes begin to not work as well.

any idea what the problem could be? i know there isnt any air in the system.

Re: brake problem
 

Have you checked the shoe adjustment, That could possibly cause a lower spongy feeling pedal.

Re: brake problem
 

no i havent checked that, why would that cause it to be spongy only past half way in the travel?

also, i DO need new brakes, including the drums turned, new shoes, new rotors, and new pads. its all on my list

Re: brake problem
 

80% of the braking power comes from the front brakes
80% of the pedal height comes from the rear brake adjustment

it's very possiable you have a bad master cyl. is it new or rebuilt?

i would do as stated.. adjust up the rear brakes. bad brakes make a truck stop poorly. and the extra fluid that has to fill the lines to make up for worn brakes make the pedal funky..low

it's not uncommon to get a bad rebuilt master cyl these days:confused:

Re: brake problem
 

yeah, it was rebuilt, cause it was about $70 cheaper than new.

how would i know if it was bad or not? its not leaking like the one that WAS on there.

how do i adjust the rear brakes again? haha havent done it in a long while.

Re: brake problem
 

have checked your wheel cyl and see if they are wet

Re: brake problem
 

i havent, but probably will. they were both replaced about 2 years ago.

Re: brake problem
 

there a inspection hole with a rubber plug on the rear of the backing plate.
you can use a brake adjustment tool or a flat blade screw driver to adjust the star wheel in side. adjust them up till you feel a small amount of tension.
while turning the wheel- drum

not to much. or you will smoke the brakes..its a touch and feel thing.

i would just plan on doing the brakes before i went to crazy..

Re: brake problem
 

yeah....

mine doesn't have the inspection hole. found that out a few years ago when i was working on the brakes then. dunno why it doesnt, but it just doesnt have anything there, no plug, no hole, nothing but metal.

Re: brake problem
 

humm. there should be a knock out on the front of the drum or the backing plate.. may not have been removed yet:rolleyes:

Re: brake problem
 

actually, i believe there is one on the drum, its about the size of wheel weight on the front of it....

Re: brake problem
 

yup thats the g spot :lol:
there should be a rubber plug with the spring hardware kit when you do your brakes :)

Re: brake problem
 

does this look like thats what it is???

http://www.ocbaud.com/pics/brakeplug.jpg

Re: brake problem
 

No, That's a weight to balance the drum....If there is a adjuster hole in the drum it could be behind your wheel spoke.

Re: brake problem
 

The hole is on your backing plate that your brakes and wheel cylinder attach to. Should be at the bottom center. If you cant find it take your brake drum off and look on the backing plate around where the adjuster star is on the bottom. Should be right there.

Re: brake problem
 

like i said, its not there, at all. i've checked every time i do brake work on it, there is no adjusting hole, i think i posted pics before the board was redone a couple years ago.

Re: brake problem
 

I don't think you have an adjustment issue. If your pedal is spongy at the bottom it sounds like you either have air in the system or the master cylinder is blown internally. New, or rebuilt it could be bad. Don't fix what ain't broke...:)

Re: brake problem
 

yeah, like i said, i'll bleed it all again this weekend, its all new fluid so i can reuse what i pump out :)

if that doesnt work, i'll go try another mc :(

i'm just happy that its "drivable" again :) got insurance put back on it today and bought a new battery so i could get it started. today was the first time in like 3 months i've drove it and the first time in 1 1/2 months that its been started.

Re: brake problem
 

well hot damn :(

priced everything out through napa for all the parts i'm wanting to get


new rotors
new pads
new drums
new shoes
2 new calipers
drum hardware kit

comes to almost $300 :(


i know it needs done though

Re: brake problem
 

Do you have a proportioning valve? On my old blazers(77-80)I had to compress the valve on its side to properly bleed the system or I would have the same thing happen that your dealing with. Also do you have a newer rearend? that would answer why there is no adjustment opening on the backing plate, at least my 99 suburban did not have one.

Re: brake problem
 

no, its the stock rear end

what exactly do i need to do with the prop. valve to bleed it correctly?

Re: brake problem
 

I also believe that you still have air in the system (or that you have a leak in the MC, Wheel Cylinder, Line/Fittings).

Here's a pic of the combination valve that Eyegore is referring:

http://67-72chevytrucks.com/vboard/a...1&d=1163735785

Depress the metering pin while performing the bleeding of the brakes. I wedged a block of wood to depress it.

A bit more information is here: http://67-72chevytrucks.com/vboard/s...d.php?t=216639

Re: brake problem
 

ok, i checked it out while angie was hitting the brakes, the metering pin is letting a little bit of fluid out of it whenever she hits the brakes.

as in, she'll hit the brakes, the pin will pop out and fluid will come out with it.....

Re: brake problem
 

think its under control now :)

bled the master cylinder again the other day and drove it a little tonight and the pedal is consistent the whole way through. i just need to bleed the lines at the wheels one more time and they should all be good to go :)

Re: brake problem
 

:cool:
Good to hear.

It took me a few times to completely bleed the air from the system when I rebuilt my brakes.