.... +1

I've had a situation while coming up to a stop light a bit hot. While I was braking (there was a good size bump in the road)as I hit that bump. My brake pedal did drop further than normal and then I had to re-apply the brake to make it work(felt like it hit the floor).Yes it did scare the crap out of me. Luckily no one was in front of me. I went back to the same spot a tried it again(same senerio) It did exactly the same thing. I don't know if it's because when I'm pressing and hitting that bump at the same time,the front wheels leave the ground and the truck senses nothing to brake on. Then when it makes contact with the road again, the brakes are already being pressed and the truck doesn't sense any brake pressure. So it drops the brake pedal down thinking I'm just applying the brakes at that moment. But,when I tried it at a slower speed not coming in hot. The truck did fine the brake pedal didn't go down any further than regular braking(not coming in hot). Anyone else experience this at all? Maybe this is what could've happened with OP wife.

You are a brave man.......

I have had that happen several times with mine. It has happened several times when I have pulled off the road trying to slow down. It has also happened when I went to cross over a bumpy paved median to pull into a driveway. The brake pedal went to the floor and the brakes didn't function. I pushed the pedal again and the brakes worked. It scares the crap out of me, but I never can replicate the situation.

Rapidly locking up the brakes while the torque converter is locked up will do this. As long as the drivers foot isn't on the brake at all before stabbing the pedal - as this will unlock the TC. If you're just cruising at 35MPH plus and jam the pedal to the floor FAST and HARD the TC can't react and it'll lockup the entire drivetrain. I know this from the design and experience side of things. This happens a lot less often with ABS vehicles, but it absolutely still happens.

However, in this scenario, if you aren't altering the force on the brake pedal, the boost from the vacuum booster gives adequate braking power, even once the engine is off, because you've already applied the brakes to the floor to lock them up. So there's usually no report of loss of braking power.

Dan

The TC lock "can't react"? You're saying that the engine will stall, like when braking hard without stepping on the clutch in a MT. I don't buy it, such a basic design flaw is extremely unlikely to not have been eliminated a long time ago

I had this happen in my FJ back in 07. Seems to me there were a few threads about this in the Blue forum. If memory serves, it had to do with the nanny's kicking in. I seem to think it was the ABS. In my situation, I was coming up to a stop sign. The road turned from asphalt to gravel and as soon as the front tires rolled off the asphalt into the gravel (Yes there was a slight drop off) It was as though I had released the brakes and rolled right through the stop sign. I was able to repeat the situation numerous times. I guess the electronics were doing what they thought they were supposed to do. I will say the first time it spooked me. I learned to get off the brakes and then reapply.

Cheers, Steve

There's no vaccuum booster in the 4th & 5th Gen 4Runners. It is supplemented by a hydraulic motor and accumulator storage tank.

Seriously? You guys have had your brakes FAIL and you haven't taken it to the shop?

Here is a quick link to just one of many threads in the Blue forum about the brakes. Worst ABS brakes ever. - Toyota FJ Cruiser Forum

Cheers, Steve

I experience this frequently offroading.

One time going down a VERY steep and rough trail, the pedal ended up down to the floor (not instantly but over a short period of time) and I had to release and press again. It was OBVIOUSLY due to the action of the ABS and possibly traction control (Basically the same mechanism). I could feel the pedal going down, down, down in jerks as the ABS/Traction control was hammering loudly on the brakes. It happened quick enough (one to two seconds) that it was rather unnerving.

I couldn't explain it in infinite technical detail, but every time the ABS/Traction system hammers a brake caliper it seems to rob fluid from the brake line causing the master cylinder to drop it's volume a bit. If you have a major incident that causes dozens of hits, it can literally drain it to the point where you need to pump the brake again.

And THEN you may get the panic brake reaction (I have). In fact besides actually hitting it fast, a press release and press again in rapid succession may also trigger it.

Pulling off the road onto dirt at some speed, going over a very rough road/board bridge and braking down steep rough terrain are all exactly the kind of scenario that causes this.

And in deference to what someone recently said, I don't think that the reaction indicates a specific failure. It seems to be endemic to the system given the number of people that experience it.

So after all that, in this very case here... what were the road conditions and did the ABS/Traction control systems actually activate? Was there a stuttering noise during the first braking? Or was this just nice smooth sailing and the pedal smoothly went to the floor with no noise at al all?

The latter would be a faulty unit. Bad presure pump or controller, etc.

But most of the other responses here are something I think most anyone can experience given the right road conditions... So just be aware of it and be ready to double pump the breaks if necessary when braking hard on rough bumpy terrain.

My guess is what they'll say is, "well since you have added aftermarket parts suspension,bigger wheels,front & rear bumpers etc.. you changed the dynamics of this vehicle". Sorry can't help you here. So for now, I have pretty much changed my driving habits just because of the added weight to the 4Runner. (Braking a lot earlier,double pumping the brakes just because,not pushing the skinny pedal as hard anymore,and a bunch more of other little stuff).

My experience was on dry road conditions. When I did hit the bump,the brake pedal did pulsate a bit while going lower to the floor before re-applying it. Now what I do when coming to a stop is hit the brakes earlier,then let off,re-apply. It's turned into a habit for me now. When I drive other cars I happen to do the double pump as well.

I've had it happen many times in my 07 FJ. I know the stretch of road it happens on. It is a down hill exit ramp off the highway that is very bumpy. It scared the hell out of me the first time.