Outer Limits 4x4 Board

recently after having shit braking performance i decided to change over the master cylinder and brake booster, and found a later model(94 sierra) booster and master and put that in
my problem comes now.
after i have put them in the calipers arent releasing properly. dragging there guts everywhere i go.
the 85 sierra uses a 13/16 sized master cyl and the 94 uses a 7/8.
would this cause problems in the system, where the different size wasnt allowing the fluid to come back out?
i have cleaned out all the pistons and they run smoothly. but i am unable to push it back in becuase of the pressure still in there.

also does the WT and NT use the same caliper. (this is what i thought, therefore didnt think it would matter)

helllp me please
zooks are slow enough as they are without having the brakes on all the time.

thanks all

I can't answer on the master cylinder issues, I thought they'd be same.
But don't assume the master is the prob.
The change may have brought out another problem.
Most common issues with Sierra front discs is
that the caliper sliders rust up, or jam up with mud.
this can cause dragging, or poor braking (may have been the initial prob)

Also masters designed for some drums hold a slight pressure on all the time, I very much doubt thats an issue, as only very early zooks had drum fronts.

christover

cylinders are perfect, slide in and out perfectly(when no pressure from fluid) cleaned them all out, seals dont leak.mines disc front aswell.
brakes are better then ever. just they get excited and dont want to ease up.

think postive *at least my brakes are good)

Spike_Sierra wrote:cylinders are perfect, slide in and out perfectly(when no pressure from fluid) cleaned them all out, seals dont leak.mines disc front aswell.
brakes are better then ever. just they get excited and dont want to ease up.

think postive *at least my brakes are good)

Sorry, I don't mean the wheel cylinder part, I meant the bits that transfer the push from one side, into a push on the other side...
there is 2 per side.
a kind of sleeve with rubber seals at each end.....tho you may actually mean those, anyway...I ain't great with terminology

yep cleaned them out aswell, they are the floating something or rathers.

Spike_Sierra wrote:yep cleaned them out aswell, they are the floating something or rathers.

guess it must be related to the new master....may need another bleed out....have had similar probs in the past that fix themselves with use...but be careful, brakes are a little important ... look into the vaacuum side of things, maybe they are getting sucked wrongly.....also consider your pedal may be out of whack, or a different fit or adjustment, and that would drag too...

good luck christover

i thought the pushrod might need adjusting. it could be putting pressure on the brakes if it wont let it come right back. this can be adjusted at the pedal if you can gull them apart.

built4thrashing wrote:i thought the pushrod might need adjusting. it could be putting pressure on the brakes if it wont let it come right back. this can be adjusted at the pedal if you can gull them apart.

yep, very possible.

rusty pivot can happen, too

pivot is fine, about this pushrod, where is it
? are you talking about the one that goes pushed the piston in the cylinder

Spike_Sierra wrote:about this pushrod, where is it? are you talking about the one that goes pushed the piston in the cylinder

yes, where it connects to the pedal and to the master...the push rod may be longer on your newer master....also looking at mine, the adjuster for the brake light switch is also the back stop for the pedal, it may need adjusting to suit new master push rod....your may be same as mine...

i broke the tip off the brake light sensor, so i took it out, so i can rule out that
i will take off the master and the pushrod thats inside the booster and check sizes and swap em over. see if that works.

you know - if i was at this point, i'd be heading down to the local mech. and asking them to take a FREE look at it and tell me what it is... which most mech's will do for you... if its easy to fix, do it yourself, if not - probably better to leave something as important as brakes to an expert =) at least if it fails you can sue/blame them!

do we have a brake bias system rear/front percentage
as i dont think the rears are staying on, only the front.
maybe the diff masters require it to be re adjusted?

Is it possible that you have the brake lines coming out of the master the wrong way round...drum brakes often have a slight pressure maintained, wheras discs do not...if you had the outputs wrong way round, could be the problem. On mine, and others I have seen, the pipe at the front of master is for the rear brakes, and the back one is for the front brakes.....split circuit later models may not be the same...
worth a look, they should be marked F or R

to the above post

the front brake lines come into a joiner down near the chassis rail seperatly.
so that this problem cant occur.
getting a kit to rebuild my old stock one, see if that will fix it.