Brake pedal goes to floor on hard braking

Hey everyone, I’ve been having an issue where the brake pedal goes to the floor on emergency braking. For example, a rabbit ran across the road and so I had to put the pedal to the metal to stop right? It was unusual because after a few seconds I thought I felt the pedal completely bottomed out on the floor. Now let me clarify, the pedal doesn’t sink to the floor on normal braking or anything. If I’m slowing down gradually, it’s a lot better. I just notice the pedal seems to dive into its travel and bottom out at times on hard emergency braking. Is this normal for first gens, because I’ve heard some mixed things on their brakes. Also I should probably note that there aren’t any visible leaks, and the brake fluid reservoir has stayed the same. The brake fluid is a little grayish, but I wouldn’t think it would cause a problem like this. Any ideas of what I should look at first? Anyone else have this kind of issue with their brakes? Also feel free to ask me any other questions concerning it, because I probably forgot something. Thanks in advance!

 

Leak in abs module or bad brake booster?

 

@empty_lord

 

Vacuum leak at the booster? Air in the brake lines? When's the last time the brake system was flushed with new fluid? Is the braking system in good order? Rear brakes adjusted? Time to do a thorough inspection and adjustment of the brakes. I wouldn't drive it if I were you until I did, next time it could be a semi that jumps out in front of you.

P.S. Brake fluid SHOUL NOT be grey. At all. It looks almost clear when new, maybe a little honey color to it.

 

It really sounds to me like you have air in the system. I would start with bleeding the brakes. I would use a turkey baster or syringe to pull old fluid out of the reservoir, replace with new fluid and start bleeding it. Don't forget the load valve. After thats done, I would find a gravel or dirt road and do the up to 20mph and slam on brakes routine a dozen times, then go bleed the brakes again.

If that doesn't help, start checking the whole system. Check that rear brakes are functioning properly and are adjusted. Check if you have brake fluid leaking anywhere. Check if there is material left on your pads up front.

If all that is okay, lookup how to check your brake booster and master cylinder. Usually if your booster goes bad it becomes really hard to stop, but your pedal shouldn't hit the floor. It would just feel like your brakes are not working and the pedal is hard to push. I

 

Ye. I’ve read air can infiltrate via old rubber hoses (permeable) and/or around rusty/crusty bleeder valves.

 

Thanks for everything so far guys. I too happen to think it might be air in the lines too. I mean if I let off and pump the brake like once, I feel like the pedal is the slightest bit firmer. As for when the brake fluid was last changed, I don’t really know since I don’t have a record of any brake fluid flush from the P.O. Have only had the truck for 6 months. Only have a receipt for pads several years ago so am not really sure about the fluid. Rears seem to be adjusted fine since parking brake works pretty well and is able to hold truck in place on a steep hill in drive. I had the wheels off and the calipers appeared with no leaks, and the pads were probably at about half thickness. No other leaks I remember seeing when I was last under there last, but might not be a bad idea to check again. Fluid level hasn’t gone down visibly. Hope that isn’t too much info i threw at you guys at once lol.

 

Air in the system or a failing master cylinder would be my bet

 

Do you mean literally to the floor? Or does it just feel that way because the pedal falls more than you think it should based on your applied pressure?

I've noticed this happen in my '14 sienna over the years during a quick stop. I haven't owned my tundra long enough to notice it at all. However, I read this in my tundra owners manual.

■ Brake Assist
Generates an increased level of braking force after the brake pedal is
depressed, when the system detects a panic stop situation.

I think it uses the ABS system to apply the brakes when you hit them hard and fast.

Like I said, I've never felt it in the Tundra, but I've felt in the Sienna a few times. It is kind of unnerving when the pedal goes light, but thr braking force is undeniable.

Edit: I'm not saying nothing is wrong with your truck, but if your casual braking is normal, I am curious if this is applicable.

 

while this is true for the newer toyotas, he has a 2004. brake assist is a relatively new thing for toyota

 

Oh man, I've crossed borders without realizing it. Carry on.

 

All good man! Lol