Topic: need some help asap with my brakes

[crawler925]

i have a 90 4runner with a rear disk swap, monte carlo calipers.... i have the marlin master cylinder that i installed two years ago.. the problem is the pedal will go to the floor when braking... it stops ok but not good enough to hold on hills... when the truck is turned off and i pump the brakes the pedal says hard and does not move but when i start it and it goes to the floor... i bled the brakes 6 times and nothing... could my M/C be bad or my booster??? any ideas guys

[NaturalDisaster]

chevy m/c will fix it ya i know it sucks to put that junk on your yota but i had to do it as well you should have a 1" bore m/c on it now and i believe the chevy master i used is a 1.1/8" bore and my truck stops very well now rolling 39"s and was doing exactly what you explained with the stock m/c and rear disc

[Cheesemaker]

Sounds like your brake booster is bad.  Generally, if you can pump up the brakes, and then turn the rig on, and it goes to the floor.  The booster is bad. 

Another thing is, did you use the residual valves?  This could be part of your problem, especially if the booster was running good before you did the swap.

[gnob]

Sounds like your brake booster is bad.  Generally, if you can pump up the brakes, and then turn the rig on, and it goes to the floor.  The booster is bad. 

booster will cause hard pedal not soft.
the pedal going lower says the booster is working.


with the key off if you pump the booster down till the pedal gets hard then put your foot on the pedal real easy, does it sink? 

generally when the pedal pushes "through" you have a master issue.  or the other thng it could be is warped rotors pushing the pistons back into the caliper, the xtra pedal is because the piston has to move further than it should normally.

[79coyotefrg]

sounds like the montecarlo calipers  are too big for the system,  a residual valve will fix part of that


other part could be air still in the line


booster??   does the negine change rpm or stumble when you press the brake pedal??  if no booster is fine,  if yes  it needs replaced

[rockhound]

I'm running rear disks. Larger bore master cylinder and proper bleeding cured my ills. You need to make sure the bleeder valve is higher then the piston. If the bleeder valve is lower then the piston on the caliper you will have air bubbles.
After I got mine working properly, I had more braking in the rear then I wanted. (locking up) I tossed the actuating arm for the brake bias thingy on the frame over the rear axle and set the rear brake pressure to a comfortable setting by trial and error. Then locked it there. you can use baling wire.