xylicon

Recently I've been noticing my brake pedal binding up and then snapping forward while braking. This doesn't happen 100% of the time, and my brakes always work, bind or no bind.

Checkout the video below of the problem, the pedal will start to depress like normal and then suddenly snap forward a few more inches. I've done a quick search on the forum and couldn't find a problem quite like mine.

https://www.youtube.com/watch?v=t7pM...ature=youtu.be

Any suggestions?

Thanks!

old87yota

I remember our resident electrical guru, RAD4Runner, had a very similar problem.

Let's see if I can find that post.

Ah, here it is: https://www.yotatech.com/forums/f116.../#post52397592

RAD4Runner and I suspected a bad brake booster was the problem but I do not know if the problem was ever resolved or what the actual cause was.

Hopefully he will chime in.

RAD4Runner

Yes, same symptoms, intermittent and no problem braking that's why I haven't touched it yet. Would rather have all parts ready first.

O.P.,
Once you come to a stop, and try doing it several times does it go away?
When the engine is off, does it EVER happen? Never in my case, which leads me to believe it is a problem with the vacuum booster.

ALL,
Consistently, before I crank, I would step on brake. Once truck starts, brake pedal does not go down like my other vehicles did. Do your guys' truck do same?

Considering finding vacuum booster and master cylinder assembly for a later year 2nd gen. That's supposed to have dual-diaphragm booster and will plug-and-play in a first-gen 4Runner. Any thoughts?

Co_94_PU

iTrader: (-1)

Not apples to apples..

The 86 only dropped about a quarter of an inch, maybe a half. (Note: 22ret w/ less than the usual 20inch vacuum)

The 94 gives a much more noticeable drop.

xylicon

My pedal will noticeably depress when I start it up, its an 88 Pickup 22RE btw.

Co_94_PU

iTrader: (-1)

Will it do what it does in the video while the engine is stopped?

Inspected the one-way valve to the booster isn't sticking?

xylicon

With the engine stopped the pedal does not do what you see in the video, instead it firms up after a couple pumps and remains firm until I start the engine, after the engine is started the pedal will depress and it will act like it does in the video if I keep pumping it.

RAD4Runner

On mine, once I stop, If I keep pumping, the problem goes away. Verify yours please?

xylicon

I'm not sure what you want me to do. Are you saying that on your truck if you keep pumping the brakes with the engine running the problem eventually goes away? If that's the case mine will not go away, it will keep binding as long as the engine is running.

Co_94_PU

iTrader: (-1)

https://goo.gl/images/7ycDn7

https://goo.gl/images/IOjjWR

These illustrate what I failed to describe properly about vents being blocked/leaking. (I hope..)