brake booster

[mark]

sometimes if im sitting at a light with my foot on the brake the pedal will quickly go down a bit.there is no fluid loss.do you think it could be the booster or the master cyl?

i have 4 wheel discs too with new pads and calipers so there should not be a lot of play there,

[J10Mike]

mark,
first of all, i don't have an answer for your question. however, nice cherokee. just one question...how do you get into the drivers seat? ladder?

mike

[J10/J20 Project]

If it holds pressure at first then bleeds down It would be your master.

[Rogue]

i agree with paul

if you pull you're master loose from booster there is prolly fluid in there, the longer you wait the more your chances that the brake fluid will eat away the rubber diaphram inside the booster

[Frankenstien]

When you take off your booster and order a new one if thats the problem make sure you pull the little spacer off the booster after you pull it from the fire wall. Don't ask me how I know this.

[Elliott]

What's the chance that his pedal may drop just because of a change in vacuum at idle?
Some cams don't produce much vacuum at idle. If the pedal dropped corresponding to a drop in idle I would think the two were related.
In a rig that size I'd bag the vacuum setup altogether and use a hydro boost.

[ November 28, 2003, 07:59 AM: Message edited by: Elliott ]

[mark]

so im drivin in the snow today and feelin pretty good that ive finally got my 4wd and everything else working properly for snow cruisin.(every other year there has been some problem)
just as i approach the street our shop is on i hit the brakes and they go right to the floor and the brake lite goes on.argggggggg
i pass the street thinking i have no brakes but a second push on the pedal and it seems ok.im sure its the master cyl because there is no fluid loss.i have a new one here ive taken off my 79.if i replace it with the new one will i have to bleed all of the fluid out of the lines to get the air out because the only real air will be at the master cyl?or if i hook it all up and pump it 1st will the air make its way down?

[youngjeeper]

that happened to me on the trails once, no brakes and brake light, pressed it again and they worked...it was a wheel cylinder. my brakes were giving me trouble a couple days ago, i would stop and the pedal would stay pressed even without my foot on it. my dad shook things around under there and now it works better then before...kinda weird

[River Beast]

If you are SURE you have no air in the lines....

Swap the lines QUICKLY to the new Mas Cyl. then BACK BLEED!!!

I use and oiler can and rubber nipple fille with brake fluid...

run the bleeder on out all the way and force fluid with the oiler can back thru the the system and the air will escape thru the Mas cyl (leave the cap off)

Of course with this method you need two people. one to backbleed and one to watch the bubles... I;ve done this a few times....

Its easier to backbleed when doing the Ma Cyl swap due to air most likely being trapped at the fitings... instead of chasing the air all the way thru the system.

a plus side is that you only have 2 fitting... one for the front and one for the rear... so you only need to backbleed on two wheels ;)

I do recommend bleeding those 2 wheel when the air is purged fromt he mas cyl....

[mark]

thanks todd
im by myself today so i think ill give it a try.ummmm would you mind running over here to give me a hand? :rolleyes:

[mark]

todd do i have to hold that little pin in at the proportionong valve while i do this?

[mark]

ttt
im doing this now
sunday 9 pm

[mark]

i just put the new one on.easy.the pedal seeems high without doin anything.im just gonna leave it tonite.if ive gotta bleed it ill do it tomorrow.

RogueStar
there was fluid behind the master cyl like you said.could have been the stock one from 76 for all i know.

[River Beast]

Sorry Mark.. just got home from a concert....

Glad it went ok....

If you need my help... get me a plane ticket... ;)

[mark]

feelt great all day today.im sure that was the prob,thanks to all who chimed in! smile.gif