brake problem

[KE20]

i got a ln130 hilux surf, the rear brakes dont seem to work, i drive along and slam an brakes and the rear ones just roll to a stop. even on wet grass they dont lockup.
ive bleed them, ive removed the drums and the shoes are good and the cylinders move when pressure is applied to the brake pedal, ive also tried the bias valve up and down, and still they dont work.
so i thought it must be the master cylinder, so i got a new one from pick-a-part today, i installed and bleed the brakes(about 6 times to make sure) and the rear brakes still dont go. im getting really pissed off and i dont know why they arent working.
if i drive the surf into a bank and get it wheel spinning and touch the brakes, they stop instantly, if i jack the rear in the air and apply the brakes they stop, but when driving they dont, what the F**K is wrong??
please help

[Crucible]

The only thing that will affect or change pressure from the mast cyl to the rear wheel cylinders would be the bias or load proportioning valve, maybe replace that first to see if it makes any differance. Even though you say youve checked it, it sounds like it could be faulty from what youve described.

Have you adjusted the rear shoes up to see if it makes any differance?

are the leading and trailing shoes the right way around?

[KE20]

it still has all the original brakes from when ever the last owner had it, probably got original stuff init. handbrake works, and i think its the bias valve aswell. ill swap with the one on my ute and see if that works, my other idea was to swap the pipes on the master around, so the front is now back and back is now front as see what happens, then ill know if its the master,
but ill try bias valve first as its easier to get to. 4wd are great, can climb underneath without jacking it up, and the 3" body lift makes life even easier.

[IH8TEC]

can you adjust the bias valves on some cars?

[matt dunn]

can you adjust the bias valves on some cars?

Hilux's have a deck load sensitive bias propotion valve as standard.

we modified one years ago to give in cabin bias adjustment on a race car.

[sergei]

With the bias valve being adjustable relative to height difference between axle and deck you will get much less braking power when the vehicle is jacked on the body, unless you are jacking on the axle...
If you jacking the vehicle from the axle and it still does not stop imideatly, try bleeding at the bias valve (it has bleeding nipple).
If everything is bled and no leaks, than you might have problem with master cylinder seals.

[KE20]

ill try bleeding the valve, but i did unbolt from the diff and cable tie up to chassis(so it thinks the back is fully loaded) and a also at full droop(so it thinks its a mile in the air) and there was no difference in braking, as in no rear brakes when driving.
im hoping its the bias valve, whats the chances 2 different master cylinders not working for the rear, and only the front????????

[KE20]

well it still dont work.
i changed the bias valvefrom my other surf(brakes all work fine) and still the same, the rear wont lock up, i even took the drums off and adjusted them, so the drums just wenton and were quite tight, but the brakes still wont lock up.
whats wrong?

[big_boy]

did you try bealding off between the master cyclender & bias valve it the valve is higher or just about the same hight as the master cyclender

[strx7]

do the wheel cylinders themselves actually work? have you determind that?

I know my surf has a bit more braking bit on the front but i put that down to new pads and discs in the front and std most likely factory rears.

[KE20]

when i had the drums off, i pumped brakes and the shoes moved out, and then sprung back when foot was lifted off the pedal.
the bias valve doesnt have a bleed nipple. just pipe in and pipe out, my other chassis has a bleed nipple on the bias, but that has 2 in(front and rear), and one out, my yn57, yn55, and yn61 both have just one in and one out, just like the ln130. im going to swap the pipes out of the master cylinder over, and see what happens, this will tell me if it the master cylinder works.
otherwise it has to be the wheels cylinders?
my other idea was to remove the bias valve, would the brakes still work okay?, or would that be too much rear braking??
this is realy anoyying me, can get cert or wof with no rear brakes.

i go flying along wet grass and the rear just roll to a stop, while the front lock up and slide, in all my other utes, all the wheels lock up and slide.

[big_boy]

douse the hand break lock them up??

[KE20]

yip, hand brake works fine, locks up sweet as

[big_boy]

how far did you push the cyclenders with the drums off as if you pushed them to far you will flip the seals causeing them not to hold pressure after that

[KE20]

not far, i pushed the pedal a few times(not to the floor tho) as ive done that to wheel cylinders before, the shoes moved out more than enough, and ive adjusted them so there quite tite to get the drums back on.
but there is no leaking of fliud from the wheel cylinders (or anywhwere), wouldnt that be the case if they cant hold pressure??

[badidas]

bend in the line mabey

[KE20]

okay
has 3rd master cylinder(this one is off my car and works fine)
brand new wheel cylinders
bias valve from my other surf(was working mint in that surf)
but rear brakes still dont work
only thing i can think of is that its the brake shoes?
but the hand brake works mints, which means the shoes are fine?
so why doesnt the rear brakes work???
help me

[rollaholic]

bend in the line mabey

[bluemaumau]

could be crushed, maybe blocked???

[KE20]

none of the pipes are crushed or bent
i am thinking it is blocked aswell, so ill put compressed airthru it today to try clear it