Breake petal sinks to the floor

[sadadar]

Need some assistance, I just bought a 1998 3.4 4runner. The brake petal sinks to the floor while driving. I have replace the front pads, bled the entire system twice, replaced the Master cylinder, replaced brake booster, and the vacuum line from the brake booster to the block. Still having the petal sink to the floor.

Other problems, I pulled the driver side drum everything inside was covered in "oil". I am guessing this is a issue with the outer axle seal, not sure.

Thanks for the help in advance, I will work on getting pictures when I get this baby road ready.

 

[kammando808]

Just did mines a few weeks ago, my problem was the brake wheel cylinder, I had brake fluid covering the brake shoes plus there was some oil that leaked around the tires, I'm positive that's you problem

 

[Parker1938]

Your problem may be a wheel cylinder leak. If the oil in your rear breaks smells like gear oil then you have an axle seal leak. This seal sits inside the axle housing.

Once you get your brake problems sorted out, update your thread with what you did. Too many people leave threads unresolved and this helps no one. Good luck.

 

[sadadar]

Just did mines a few weeks ago, my problem was the brake wheel cylinder, I had brake fluid covering the brake shoes plus there was some oil that leaked around the tires, I'm positive that's you problem

Replaced the brake wheel cylinder, still have a petal that sinks to the floor......Any other ideas?

 

[tacojeff]

Does the fluid level drop? Does the pedal have any resistance difference throughout the stroke? Can you stop engage the brakes at all?

If you don't have an external leak, I wonder if the ABS valve block could be at fault. Although a crude method, you could buy some female brake line caps, to put on the end of the various hard lines, and cap the lines at various points to isolate sections of the system. Then see if the pedal gets hard, if so move further down the lines.

 

[JRZEE2000TR4LTD]

Need some assistance, I just bought a 1998 3.4 4runner. The brake petal sinks to the floor while driving. I have replace the front pads, bled the entire system twice, replaced the Master cylinder, replaced brake booster, and the vacuum line from the brake booster to the block. Still having the petal sink to the floor.

Other problems, I pulled the driver side drum everything inside was covered in "oil". I am guessing this is a issue with the outer axle seal, not sure.

Thanks for the help in advance, I will work on getting pictures when I get this baby road ready.

Does the pedal go to the floor with the truck off? The wetness in your drum could be as you said. If it looks almost like grease then is your axle seal(s) which would mean seals, bearings, and differential breather replacement, need to be looked at.

 

[LittleCaesar]

Bubbles in the fluid?

One or more brake hoses may be shot, especially if the previous owner(s) considered brake fluid to last the life of the 4runner.

 

[kammando808]

Double check the brake hoses, if you haven't replaced them one of um might be old and have cracks which can cause them to expand while your stepping on the brake pedal??

 

[ben992]

I am having the exact same problem with my 96. I had leaky wheel cylinders, replaced both, bled brakes twice. I am not loosing fluid like I was with the wheel cylinders--all that is new. Pedal goes to the floor, don't know why...interested in how this goes.

 

[nissanh]

Mc

Need some assistance, I just bought a 1998 3.4 4runner. The brake petal sinks to the floor while driving. I have replace the front pads, bled the entire system twice, replaced the Master cylinder, replaced brake booster, and the vacuum line from the brake booster to the block. Still having the petal sink to the floor.

Other problems, I pulled the driver side drum everything inside was covered in "oil". I am guessing this is a issue with the outer axle seal, not sure.

Thanks for the help in advance, I will work on getting pictures when I get this baby road ready.

Did you buy the parts from auto-zone?

 

[sadadar]

Did you buy the parts from auto-zone?

I purchased the Master Cylinder from Auto zone......


After a 2 day break, I bled the brakes again this morning. Used almost a small bottle of brake fluid. The pedal is much less travel. I think the wheel cylinder on the drum and bleeding the brakes fixed the issue.


Thanks for all the help, now to get the shocks and struts replace.

 

[325runner]

Did you bench bleed the master cylinder properly..I would try bleeding the master cylinder at the lines that come off the master cylinder then follow that with a full system bleed.if that don't work swap it out for another

 

[RTI]

ABS system needs to be bled as well. Easiest way to do this is bleed the brakes, cycle the ABS system by locking up the brakes, bleed brakes again.

I would recommend to find a dirt road or parking lot where you can safely reach about 15mph and then stomp on the brakes to activate the ABS.

 

[SgtAbn]

3rd generation 4Runners are kind of known for having under equipped brakes, that is why so many people go to the larger Tundra front brakes or and/or change the rears out to disc brakes.
I have the same problem you do + a 0171 trouble code. I checked the vacuum lines and found no cracks so I took it to the dealership. They said I need a new 'brake booster" which is the large diaphragm behind the master cylinder. They want $1400 (parts / labor) but they will only guarantee the part for a year. I found a very good (and simple) YouTube video showing how to swap out the brake booster and I can find used ones locally / online for $60 -$100 so that's what I am going to do. I have heard there is a way to put in a upgraded master cylinder with a larger diameter main tube which will make the truck stop faster / make the brake pedal more sensitive but I cant find a upgraded master cylinder or brake booster anywhere.. . Any info on how to upgrade the brake booster or master cylinder would be greatly appreciated. ..