toyota brake problem

[big cherokee]

ok guys have been running with this problem for a while and need to get it fixed.


set up is 86 yota with v6 calipers up front with vented rotors off a fj,
master cylinder and brake booster are off of a t100 (dual diaphram booster and 1in bore master) rear axle has 11in drums off a 96 4runner

i also ran new hard lines to the rear of the truck since the other ones blew out 3 years ago due to rust, also have breaded brake lines and removed the load sensing valve in the rear.

rear drums are all new and adjusted but the problem im having is i can not lock up the rear wheels at all. fronts will lock up great but nothing in the rear, i have pressure back there as when i had the drums off had the wife push the pedal and everything moved.

i have used the brake bleeding machine at work and put a half gallon of fluid threw the system still nothing to the rear.


1 i think its a bad master
2 incorrect adjustment on rear drums
3 i have no more ideas.

anyone help please.

 

[sixstringsteve]

check your proportioning valve. It's the valve that adjusts the flow to your rear brakes, based on the load you're carrying.
[EDIT] Trailblazer beat me to it.

Also, what size tire are you running?

 

[sixstringsteve]

I would think that removing the prop valve would make it easier to lock up the brakes, not harder. The way I understand it, the prop valve "open" and provides more flow as more weight is added to the truck. THe heavier the load, the more fluid is allowed to pass through, thereby giving the rears more stopping power.

 

[sixstringsteve]

Yeah, but I didn't fully read - he removed that load sensing valve.

Oops, I missed that too.

I know that on the tacomas (and I would assume the '96 4runner are the same) the e-brake resets and calibrates the drum brakes somehow. That being said, I've never been able to lock up my rear brakes on pavement with any tire size over 33" in ANY of my toyotas.

Are you able to stop ok, or is it really weak in the rear? I guess I'm asking if your goal is to lock the rear brakes, or just have the power you need to stop well?

 

[sixstringsteve]

I'm out of ideas.

 

[Rot Box]

I've always just eliminate the proportioning valves--no need for an aftermarket unit imo. Does your petal feel fine? Or does it go to the floor before anything works?

What type of machine are you using to bleed the brakes? If vacuum do you keep getting bubbles in the line or solid fluid? Use teflon/thread tape around the bleed nipples if are getting air...

Assuming you DON'T have a LSVP my bets are in this order:

1. Master not properly bench bled.
2. Air in rear lines.
3. Rear wheel cylinders out of adjustment.

If your front brakes work you can rule out the master cylinder.

My rears sucked for a long time. They would only lock up on ice/snow until I invested in a vacuum bleeder. A vacuum bleeder can rule out a lot of variables. Hope any of this helps,

Andrew

 

[big cherokee]

its a valvoline machine that actually forces fluid in to the reservoir and uses vaccuum to suck it out.

no airbubbles when flushing, i was thinking of switching hard lines also,

with the valve out of the back they say they should lock up with any tire under 35s im running a 40in tire.

pedal is a little soft, fronts lock up rears just role in 4 low up on the hoist i can not stop the rear tires but fronts lock up. i will switch hard lines and bleed again and see what it does.


i just know running hells revenge i want all my brakes and coming off the steep decline running behind the rocks backwards was a little sketchy also.

 

[sixstringsteve]

i just know running hells revenge i want all my brakes and coming off the steep decline running behind the rocks backwards was a little sketchy also.

I hear ya, with an automatic, brakes are crucial in moab!

 

[big cherokee]

i think i well also adjuste the rear shoes out a little tighter on the drums also.

im not running a ebrake on the the axle so i cant use it to reset the shoes.

 

[big cherokee]

ya the 4l60e engine brakes pretty good but some of the places are way steep in moab. rather have to much than not enough.