Soft brake pedal

[Doc2012]

Because it uses pressure to force the master cylinder To push fluid.

Kind of like your hydraulic system. You've it to have a pump to get the pressure, right?

The booster increases pressure from the pedal and adds more to the MC. If your booster is bad, you're not getting that pressure to the MC, so you're pedal goes to the floor and doesn't stop the truck as well as it should.

I pulled the ABS fuse out of my truck, and didn't have an issue for a long time. Then, I completely lost pressure in my brakes. Tried everything. Even went as far as to get a manual MC, and took out the ABS pump and ran lines from the MC to each front wheel and the back lines. Still had soft brake pedal. Swapped the booster out and pedal instantly changed.

 

[jeremyc74]

Because it uses pressure to force the master cylinder To push fluid.

Kind of like your hydraulic system. You've it to have a pump to get the pressure, right?

The booster increases pressure from the pedal and adds more to the MC. If your booster is bad, you're not getting that pressure to the MC, so you're pedal goes to the floor and doesn't stop the truck as well as it should.

I pulled the ABS fuse out of my truck, and didn't have an issue for a long time. Then, I completely lost pressure in my brakes. Tried everything. Even went as far as to get a manual MC, and took out the ABS pump and ran lines from the MC to each front wheel and the back lines. Still had soft brake pedal. Swapped the booster out and pedal instantly changed.

There's no way the booster is causing the pedal to go all the way to the floor. The only way the pedal goes to the floor is if there's air in the system, a leak, or a cylinder is bypassing fluid.

All the booster does is use engine vacuum to assist you pushing the pedal. If the booster is bad the pedal gets harder to push.

Besides that, it's easy enough to check. All you have to do is push the pedal with the engine turned off. There's no vacuum at all then.

 

[Doc2012]

There's no way the booster is causing the pedal to go all the way to the floor. The only way the pedal goes to the floor is if there's air in the system, a leak, or a cylinder is bypassing fluid.

All the booster does is use engine vacuum to assist you pushing the pedal. If the booster is bad the pedal gets harder to push.

Besides that, it's easy enough to check. All you have to do is push the pedal with the engine turned off. There's no vacuum at all then.

I'm telling you from my experience.

What's it gonna hurt to try it?

I put a new booster in my truck and my brakes were great.

 

[LittleCaesar]

I guess I will ask when you initially changed the front pads when you retracted the piston did you crack open the bleeder valve at the caliper?

 

[mwrohde]

I guess I will ask when you initially changed the front pads when you retracted the piston did you crack open the bleeder valve at the caliper?

Are you asking me? I never changed the pads in this truck. I've only owned it a couple of weeks.

However, I have now had the entire hydraulic system open. I've changed the front soft lines, put new rotors on it, and replaced the master cylinder (twice).

I've tested the booster to the best of my ability. With my foot on the brake pedal and the truck off I started the engine. The pedal became much easier to press.

With the truck off and applying constant pressure to the brake pedal it sinks . . . . much further than I have experienced in other vehicles.

I've pulled the ABS fuse (that was a *****), and there was no difference in the pedal travel or feel.

What I think is the ABS pump (near the firewall, passenger side, bunch of hard lines in/out of it) clicks three times when I turn the key on. I've never heard the pump prime.

The truck stops well. Maybe that's just how the brakes are in this truck?? They certainly are different than anything else I've driven, though.

 

[Mynameistommy510]

How many clicks does it take to bring your hand brake up? The rear drums are self adjusting but the adjusters commonly become seized.
I've heard of people over adjusting them manually just by a few clicks intentionally for a better braking feel.

 

[mwrohde]

How many clicks does it take to bring your hand brake up? The rear drums are self adjusting but the adjusters commonly become seized.
I've heard of people over adjusting them manually just by a few clicks intentionally for a better braking feel.

I haven't counted the clicks, but I've been very careful with them. I pulled the drums, cleaned them, put them back on, over adjusted them, pulled the drums to under adjust, and re-adjusted with the e-brake handle.

E-brake has a real good feel and works well. I'm very certain this is a hydraulic problem. I just don't know if I've got a 3-in-a-row bad master cylinders or if there's something screwed up in the ABS system.

 

[LittleCaesar]

My guess is with the latter. If the mechanic comes back and tells you your ABS modulator is shot, find a used one.

The reason I asked about changing the front pads is once I was changing out pads on a Camry with 60K miles on it. Instead of cracking open the bleeder at the caliper I just pushed the cylinder back in. For a month the owner got a soft pedal now and then. I had to take the car to Toyota to get them to activate the ABS, then they bled it. I tried six different bleeding methods with none of them yielding any long terms positive outcomes.

Let us know how it goes.

 

[nevada]

Explain that to me. How could that cause the pedal to sink to the floor? There's not fluid in that at all, right?

it wont.
but you can eliminate it by pulling the vacuum hose off, then checking the pedal.

Because it uses pressure to force the master cylinder To push fluid.

Kind of like your hydraulic system. You've it to have a pump to get the pressure, right?

The booster increases pressure from the pedal and adds more to the MC. If your booster is bad, you're not getting that pressure to the MC, so you're pedal goes to the floor and doesn't stop the truck as well as it should.

I pulled the ABS fuse out of my truck, and didn't have an issue for a long time. Then, I completely lost pressure in my brakes. Tried everything. Even went as far as to get a manual MC, and took out the ABS pump and ran lines from the MC to each front wheel and the back lines. Still had soft brake pedal. Swapped the booster out and pedal instantly changed.

no, that's not how that works.

There's no way the booster is causing the pedal to go all the way to the floor. The only way the pedal goes to the floor is if there's air in the system, a leak, or a cylinder is bypassing fluid.

All the booster does is use engine vacuum to assist you pushing the pedal. If the booster is bad the pedal gets harder to push.

Besides that, it's easy enough to check. All you have to do is push the pedal with the engine turned off. There's no vacuum at all then.

this.

 

[Mynameistommy510]

Have you checked to see if fluid is seeping through your wheel cylinders? The rubber boots on the ends of the cylinders can hold and hide fluid getting past the cylinder. Pull back the boots with your fingers to see if fluid is in them.

As well check for uneven wear in your brake pads. Could be a bad cylinder in your caliper. I have no experience with how this could effect pedal feel.

I wouldn't rule anything out with brakes. Most likely hydraulic but you may be surprised.

 

[mwrohde]

I think I won.

I bought an ABS pump from a junk yard. I installed it this morning and did all the associated work. My wife, who is real particular about brakes, said they are perfect.

What an ordeal!

I'm taking next weekend off (from car work (unless something breaks)). I'll probably do the valve cover gaskets the weekend after that.

 

[stever1000]

Read through this for the third time and I'm beginning to think I need the ABS pump too.

I replaced all my soft lines, new fluid, new master cylinder, adjusted rear brakes, and the pedal still sinks to the floor as your describe

 

[xcmountain80]

A year or so ago my VSC (IIRC) light came on. The vehicle was aging so I thought nothing of it and just chalked it up to a failed component. The ABS started acting up and engaging EARLY, stopping was impossible because as soon as you hit the brakes in normal driving situations it would berrrrrrrr and the pedal would hit the floor.
I promptly replaced the 4-wheel speed/ abs sensors and ordered a used ABD ECU on eBay. Replaced all, and still had the problem, I think I also unplugged the + terminal for about an hour hoping the system would clear and learn.
Not wanting to risk it I engaged my abs/vsc kill switch and carried on. Recently 2 months or less I noticed when backing into my spot at work the pedal would go soft, 2 pump got it back to firm and grabby.
I just started to notice it doing this in traffic moving forward, it is a little soft then a second pump of the pedal firms them up. Now the truck has 440,440 miles and I know components will fail, I just need to figure out which one it is and fast. Yes the truck has the Tundra brake upgrade, and no I have had no issues. I did a rear wheel seal last week, bled per the instructions.

I have no visible leaks on the calipers front or rear.

 

[toverturf]

After reading all this I think I need a ABS pump also. I've replaced all my soft lines with stainless steel, new oem master cylinder, new rear pads and drums, parking brake works, rear cylinders are good, don't notice any leaks anywhere or loss of fluid, and have bled it a ton. I think my next step will be going to a junk yard and see if I can find a ABS pump.

 

[toverturf]

Got a junkyard ABS pump installed today and my brakes are so much better. I had no ABS light or codes saying it was bad.

 

[eaglesroost2]

soft brakes issues 4 runner

Frustrated with soft breaks in our 2021 TRD Offroad model 4 runner.

The brakes are noticeably soft when pressing down on the brake pad. I am comparing these brakes to our 2015 TRD Pro 4 runner and recently purchased 2022 SR5 premium 4 runner, both of those have normal quick response brakes. I took the 2021 4 runner to Lithia Toyota in Montana and was told after inspection the brakes and soft response was normal?? But comparing to my two other 4 runners I think they are either giving me a line of Bull or do not know what they are talking about.

Anyone with same issues or suggestions ???? We have not bled the brake lines yet just had Toyota inspect the calipers, pads etc...Frustrating to say the least...wondering if this could be a hidden factory defect issue toyota is not talking about.

 

[Riceye]

Frustrated with soft breaks in our 2021 TRD Offroad model 4 runner.

The brakes are noticeably soft when pressing down on the brake pad. I am comparing these brakes to our 2015 TRD Pro 4 runner and recently purchased 2022 SR5 premium 4 runner, both of those have normal quick response brakes. I took the 2021 4 runner to Lithia Toyota in Montana and was told after inspection the brakes and soft response was normal?? But comparing to my two other 4 runners I think they are either giving me a line of Bull or do not know what they are talking about.

Anyone with same issues or suggestions ???? We have not bled the brake lines yet just had Toyota inspect the calipers, pads etc...Frustrating to say the least...wondering if this could be a hidden factory defect issue toyota is not talking about.

So, you're saying that your 2021 TRD Offroad 4Runner doesn't have as nice a feel of the brake pedal as your 2015 TRD Pro 4Runner or as your 2022 SR5 Premium 4Runner?

First, you're in the wrong forum. This is for 3rd Gen 4Runners (96 - 02). Your 2021 TRD Offroad 4Runner is a 6th Gen.

Second, you have an enviable problem.

Good luck!

 

[spartacus]

Frustrated with soft breaks in our 2021 TRD Offroad model 4 runner.

The brakes are noticeably soft when pressing down on the brake pad. I am comparing these brakes to our 2015 TRD Pro 4 runner and recently purchased 2022 SR5 premium 4 runner, both of those have normal quick response brakes. I took the 2021 4 runner to Lithia Toyota in Montana and was told after inspection the brakes and soft response was normal?? But comparing to my two other 4 runners I think they are either giving me a line of Bull or do not know what they are talking about.

Anyone with same issues or suggestions ???? We have not bled the brake lines yet just had Toyota inspect the calipers, pads etc...Frustrating to say the least...wondering if this could be a hidden factory defect issue toyota is not talking about.

Different runners have a different feel. Some are harder others are softer. As long as it stops adequately. Have to get used to it.

 

[Devbot]

Well this has been a mixed feeling thread. I was suspecting an ABS pump at this point which feels reassuring I might be on the right track, but also means I gotta deal with bleeding all over again
I replaced my brakes last year (regular replacement, no TBU) and ever since have had a soft pedal and usually needs pumping to help stop - my "new normal" since then is NOTHING happening for around 75% of the pedal travel before finally catching, but even then it feels like maybe half the strength as it did before. Pumping the brakes even just once drastically improves how they feel and perform (which usually means water or air, right?)
My fluid was super old and pine green color so I assumed it had a good amount of water and general age to it, but since then I've had my brakes bled over a dozen times and NOTHING helps. I've bled them every way under the sun including the FSM and every possible method I could find on T4R, I've activated ABS several times, completely drained and replaced the fluid, and checked for air bubbles more times than I can count. Post bleeding it always feels great - until the SECOND I pull out my driveway and come to a stop from full speed (25mph or so). The longest improvement I saw was roughly 40 minutes of driving total and even the two other people I've gotten involved are stumped as well. :smashputer:
I DID get an ABS code randomly at some point last year than went away on it's own before I could check it; it never came back and from what I can tell the ABS is functioning totally fine when it's required... should I still gamble on one, do you guys think? It's hard to justify it without knowing for sure something is wrong... but at the same time you can also find them for half the price of a master cylinder

 

[brillo_76]

Well this has been a mixed feeling thread. I was suspecting an ABS pump at this point which feels reassuring I might be on the right track, but also means I gotta deal with bleeding all over again

I replaced my brakes last year (regular replacement, no TBU) and ever since have had a soft pedal and usually needs pumping to help stop - my "new normal" since then is NOTHING happening for around 75% of the pedal travel before finally catching, but even then it feels like maybe half the strength as it did before. Pumping the brakes even just once drastically improves how they feel and perform (which usually means water or air, right?)

My fluid was super old and pine green color so I assumed it had a good amount of water and general age to it, but since then I've had my brakes bled over a dozen times and NOTHING helps. I've bled them every way under the sun including the FSM and every possible method I could find on T4R, I've activated ABS several times, completely drained and replaced the fluid, and checked for air bubbles more times than I can count. Post bleeding it always feels great - until the SECOND I pull out my driveway and come to a stop from full speed (25mph or so). The longest improvement I saw was roughly 40 minutes of driving total and even the two other people I've gotten involved are stumped as well. :smashputer:

I DID get an ABS code randomly at some point last year than went away on it's own before I could check it; it never came back and from what I can tell the ABS is functioning totally fine when it's required... should I still gamble on one, do you guys think? It's hard to justify it without knowing for sure something is wrong... but at the same time you can also find them for half the price of a master cylinder

Maybe you done this and I missed it. Are your wheel drum brakes adjusted up properly and your emergency brake functioning properly? As I personally have seen major pedal soft pedal from those not being adjusted up.

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