Another, but different BRAKES thread

[PitbullRescuer]

I've had the touchy brakes and all. Got used to it, it's fine.

Today, was cruising down a 2 lane road at about 55 or so. Was going down hill, light turned red, got on the brakes a little hard. The pedal travelled literally about 1/8" and then got rock hard. Lifted, same thing. Stood on them to stop, never locked up but almost felt like the eBrake also engaged. There was a gas station about a .25 mile ahead so I pulled over, shut it off and gave it a once over. Everything looked fine underneath. Fluid level is fine. Started it back up and it was back to normal.

Any ideas?

 

[rigtec]

I've had the touchy brakes and all. Got used to it, it's fine.

Today, was cruising down a 2 lane road at about 55 or so. Was going down hill, light turned red, got on the brakes a little hard. The pedal travelled literally about 1/8" and then got rock hard. Lifted, same thing. Stood on them to stop, never locked up but almost felt like the eBrake also engaged. There was a gas station about a .25 mile ahead so I pulled over, shut it off and gave it a once over. Everything looked fine underneath. Fluid level is fine. Started it back up and it was back to normal.

Any ideas?

Hi pbr,

I've noticed that every so often my truck will do something kinda wacky like a security system glitch, navigation hic-cup, or just the way it shifts... could be anything that gets my attention. But I've learned not to be so critical (anal). I actually can ignore most of the small stuff cuz I've had the truck now for four yrs so I never panic. There are several computers (ECUs/ECMs/PCMs, yada, yada, yada) working together in a network. Every now and then they'll be a hic-cup.

Sometimes it'll resolve itself, sometimes it needs a master reset just like your microsoft windows machine needs an occasional restart. Sometimes you can perform a reset yourself by disconnecting the main battery, leaving it disconnected for a couple hrs (4 minimum IMO) and the truck'll be just fine afterwards! Most of the systems in the truck are soft/firmware driven and so need a lil' TLC from time to time, being subject to temperature extremes, static and constant electrical surges! Keep that in mind and sleep at night... as you should, lol!

Cheers

 

[FrontRange4Runner]

Vehicle year and millage? Have the brakes ever been replaced? Weather conditions? I'm assuming you lost brake effectiveness when the pedal went solid which is sketchy. Have you gone out and slammed them again? May have just been a fluke, but you should have it checked over by a pro. The e-brake can't be engaged by the vehicle and does not need to be, the brakes are more than adequate to lock the tires (ABS should engage if this happens though). What makes you say the the e-brake felt engaged? Sorry, lots of questions, but info helps people better understand the problem.

 

[PitbullRescuer]

Good questions. It's a 2015 SR5P with 12,000 miles. Weather was dry. Hard to describe what it felt like, best I can say is it felt like it was hopping to a stop. Which I guess it was since it would nose dive as I was touching the brakes and would come back up as soon as I lifted. The brakes felt like an On/Off switch. I did try a hard stop again afterwards and it was fine although it was on flat ground rather than a down hill.

Anyone else ever have anything like this happen?

 

[e60ral]

it sounds like your ABS came on and did what it was supposed to

when ABS comes on the pedal will suddenly feel soft and not give you the linear feedback you felt up to that point

 

[1engineer]

Good questions. It's a 2015 SR5P with 12,000 miles. Weather was dry. Hard to describe what it felt like, best I can say is it felt like it was hopping to a stop. Which I guess it was since it would nose dive as I was touching the brakes and would come back up as soon as I lifted. The brakes felt like an On/Off switch. I did try a hard stop again afterwards and it was fine although it was on flat ground rather than a down hill.

Anyone else ever have anything like this happen?

Here's a post I did several years ago in response to the same type of situation. See if this might help:

"Pretty sure your dealer is full of shit. That said, I don't think ABS is technically to blame here either. It sounds like your brake assist function is the causation of your consternation or really, the actuation of the brake assist feature.

Here is what I know from personal testing:
When applying the brakes on the 4Runner with a slow, steady force, you can get to the ABS actuation without the brake assist function kicking in. If you "panic" brake, that is stab quickly and hard on your brake pedal, you will bring in the brake assist and MAN does it assist! I did this test when I owned the 2011 SR5. I was intrigued by this braking system after panic braking for a deer and stopping right. now. so I went out to a stretch of deserted highway and decided to figure out how this works. I got up to 50 mph and slammed on the brakes. I mean hit it hard and fast just like a panic stop. The brake assist kicked in and I stopped really really fast. I then got up to 50 mph again and gradually (by gradually I mean less than a second but not instant) applied increasing force to the brake pedal. The ABS kicked in but no brake assist! I did it a few more times with varying degrees of actuation force and speed and determined that the brake assist actuation has to do with the velocity over time before it was activated. What does this mean for you?

Take your 4Runner out, much as I did, to a deserted stretch of road and start testing. Make your maneuvers as you would normally do, then go back and do them using a slower actuation speed, meaning don't instantly but gradually push the brake pedal. Report back.

I actually changed the way I brake with the 4Runner after my testing. Brake assist is a great tool to augment stopping but I, like you, would prefer more control during the braking process. Now in a true panic stop brake assist is going to happen (instinct) but for all other situations slow(er) than instant actuation might just help you."

 

[TrkyMfns]

Sounds like the robo brake aka brake assist kicked in.

 

[PitbullRescuer]

Sounds exactly like what happened. Oddly enough, in the past that would usually lock up the tears for a second. What threw me this time was the pedal being rock hard. Messed with it today a bit on my way to office and everything seems fine again.

Thanks for the input fellas. Much appreciated.

 

[Tusa123]

1engineer, thank you so much for the write up on the subject. I recently purchased a 2015 LE and have experienced the panic braking with the "assist" and it's very alarming. I too thought there was an issue because I've felt the ABS kick in and it is a very different feeling. My 14 Tundra did the same thing so I didn't get too concerned; its good to know it's intentional and a "safety feature". Thanks again!