roundhouse

Decided I may need to replace my master cyl on a 96 4wd, rear brakes no longer work, fronts work fine, bled it till I was blue, no help, pedal is spongy.

I recall reading somewhere that some special computer is needed to run the ABS pump to bleed out the air?

Any other way to do this?

thanks

97ltd4x4

The ABS actuator should provide an open path for brake fluid to travel.According to the service manual,you do not need to bleed the ABS actuator after a master cylinder replacement,since it just acts as an open brake line loop.

Did you bench bleed the master before you installed it?

Did you adjust the push rod?

Is the push rod long enough to engage the master cylinder pistons(has two connected by spring)?

what to do if you are sure the push rod is set correctly,bleed master in car...disconnect lines,have someone put fingers over master line ports,fill fluid,have someone slowly pump petal,this will move lots of fluid out of master*****will make big mess,use nitril gloves***,when only fluid comes out or about 1/2 can brake fluid,reconnect lines at master..Or remove master and bench bleed master..this is critical if any trapped fluid in master no mater how much you bleed,will always be spongy..

have several cans of brake fluid on hand,take all 4 wheels off,open all bleeder screws..let fluid gravity bleed use 2 cans of fluid..tighten all the lines up.. how does pedal feel now?..might have to bleed one at a time now if still a bit spongy

***Note:all this should be done with the car off******

trd_4runnin11

I just went through this with my 98.

When you bleed the brakes you want to start farthest away from the master cylinder and work your way towards it (PR, DR, PF, DF). Do it until the fluid runs clean. Brake fluid is pretty cheap. This might take a while, I was getting some air even after bleeding each corner multiple times. Also, one thing to check.. there is a little gasket between the master cylinder and brake booster. Mine went bad and there was a slow leak from there. The gasket is like $2 and takes about 5 minutes to replace, but if yours is bad you will see brake fluid running down the brake booster and it doesn't take much for it to start affecting your braking.

How many miles are on your 96? Master cylinders don't normally just go out for no reason. If its been ran for a long time low on fluid that would make some sense, but I would try some other things first.

roundhouse

There is no air in the lines , ive bleed it lots.

The gasket at the MC looks ok.

Truck has 260,000 on the clock.

hatda02

Will the brake pedal stiffen if you pump it a few times?

Have you checked the rear shoes and make sure they are adjusted to the drum?

If you have one, or both, of the rear wheels off with the drum off and someone presses the pedal, does the slave cyl move the shoes at all?

roundhouse

No,

yes,

yes.

changed the shoes and drums, thinking the drums were worn out to large.


The longer you hold your foot on the pedal the softer it gets,

If I mash the pedal hard, and hold it, after about 40 seconds it starts slowly going to the floor.

97ltd4x4

whith that kind of milage,how are your rear wheel cylinders? did you peel back the boots and check for seapage? also how were the brakes before the master cylinder install? Was the master cylinder suppose to fix the problem? And did you bench bleed the master?

roundhouse

I havent swapped the MC yet, wanted to get info regarding the ABS pump first.

hross14

Working all day to figure out your breaks--Priceless

$1500 (dealer i do believe) to replace the ABS pump--Insanity

It really sounds like you have the classic case of master-cylinder-itist

reasoning--When you pump up the brakes and then slowly hold it down it the pedal will go down slowly.

But if as stated above--all the wheel cylinders/calipers are ok--you have bleed like crazy--it points to a leak or bad M.C.

BIC performance

My brakes are the same way on my 96. Well the rears work, I just get major nose dive when I hit the brakes. All the shoes, pads, rotors and drums were replaced, I also replaced the master cyl, and I still have a mushy pedal, and my rear shoes are adjusted. I wonder if it could be the brake booster?, does anyone have a TSRM link for a 96 runner?, I am not sure how one would go about testing a booster.

hross14

Come to think of it--my 97 4Rnr did the same thing--i just thought it was how the brakes worked on that vehicle. But I could hold the brake down and it wouldnt go down slowly.

Everything worked--but that was just the way the brakes were--so i think it is a design snaf--foo

My 99 brakes dont do that

roundhouse

Will the 99 booster and MC fit on a 96?

roundhouse

Anyone know where I can get a booster?

NAPA wants $500 for it!

hross14

junk yard--why do you think it is the booster?

roundhouse

If I stop and hold the brake pedal down, kill the engine and keep my foot exactly the same after about 60 seconds the pedal starts pushing itself up and will release the brakes, no matter how hard you try to mash the pedal.

I think the MC is leaking down as well, if I sit with my foot on the brake at a long traffic light or or something, the pedal slowly goes down.

The truck has 278K on it, so it seems plausible that the booster and MC are worn out.


I have a MC and booster from a junkyard ordered, and looking for tundra calipers & rotors.

Will rotors & calipers from a 2WD Tundra work for the swap?