1998 Persistent Soft Brake Pedal

[blarchitect]

'98 had a soft pedal which got worse. ABS light would come on after driving a few minutes.
Changed master cylinder, both rear wheel cylinders and after reading the other thread I also got a used ABS pump. Bench bled MC. and bled brakes twice but SOFT pedal remains. Pedal is quite firmi with engine off. My fluid was old so first time I bled I changed it using the Allstar One man Bleeder Bottle.
There still can't be air in the system right? This is driving me nuts. Any help or pointers would be appreciated.

Oh, coz I can't drive it I don't if I have solved the ABS light issue.
Thanks

 

[blarchitect]

One other thing- there is a hiss or air sound coming from the booster audible inside cab when i press pedal, that i don't recall hearing before.
I have a replacement booster but loathed to change it this is just clutching at straws. Is there definitive way to test booster? What should happen when I pull the large vacuum hose?

 

[Bad Luck]

'98 had a soft pedal which got worse. ABS light would come on after driving a few minutes.
Changed master cylinder, both rear wheel cylinders and after reading the other thread I also got a used ABS pump. Bench bled MC. and bled brakes twice but SOFT pedal remains. Pedal is quite firmi with engine off. My fluid was old so first time I bled I changed it using the Allstar One man Bleeder Bottle.
There still can't be air in the system right? This is driving me nuts. Any help or pointers would be appreciated.

Oh, coz I can't drive it I don't if I have solved the ABS light issue.
Thanks

Sounds like air in the system still. Did you follow the FSM procedure for bleeding the master?

 

[TucsonMike]

Hissing sound for brake booster usually indicates bad brake booster. That was the symptom I had on mine and my friends 4runner when they started going bad. Good luck
MikeM

 

[19963.4lsr5]

What procedure did you use to bleed the brakes?

If you don’t have a pressure bleeder the below….

The best is gravity bleed first, then open bleeder-depress pedal to the floor-close bleeder- release pedal. Rinse and repeat.

If you’re a brake pumper you took a few bubbles and compressed them into millions.

Then activate the breaks abs system and repeat untill the pedal pressure does not change after the abs activates.


Sent from my iPhone using Tapatalk

 

[blarchitect]

I used this method and video to bleed brakes. One man operation
Brake Fluid Bleeding / Flush (One Man) - 3rd Gen Toyota 4Runner - YouTube

The brake pedal moves down when engine started so I believe booster is good. Wouldn't the pedal be rock hard if it was bad?

I bled the MC twice once using: the tubes that feed back into reservoir (sh1t method as they fall out) and the solid plugs on attempt #2.
Guess i should get a helper and try the FSM method.

 

[prybar]

I had similar symptoms you're describing. Brakes went out in traffic, and it ended up being the brake booster. Very easy swap. OEM boosters are super expensive and aftermarket brake booster seems shady. I ended up getting one from the auto recyclers yard for about $30 if this helps.

 

[phattyduck]

Bench bled MC.

Did you follow the FSM instructions to a T?

They aren't normal procedures for the MC bench bleed, and the order of the rest of the bleeding is important too.

Also, see if you can get an ABS activation, then bleed again - rinse and repeat. That should also help improve performance. It is hard to clear the ABS unit if it gets air in it.

-Charlie

 

[blarchitect]

Thanks for replies. I will use FSM method.
How does one activate ABS when the vehicle is stationary?

 

[phattyduck]

Thanks for replies. I will use FSM method.
How does one activate ABS when the vehicle is stationary?

You don't. That's what dirt is for...

You should be able to get it reasonably ok with the FSM procedure, but the last 25% of the way will take ABS actuation while driving.

-Charlie

 

[blarchitect]

You don't. That's what dirt is for...

You should be able to get it reasonably ok with the FSM procedure, but the last 25% of the way will take ABS actuation while driving.

-Charlie

Ok. Hopefully I regain 75% because at the moment the pedal goes to the floor will little stopping power. Will update.

 

[phattyduck]

Ok. Hopefully I regain 75% because at the moment the pedal goes to the floor will little stopping power. Will update.

That's how mine was after using a 'normal' bleeding procedure after a Tundra brake upgrade and new master cylinder...

-Charlie