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Discussion Starter #1
My `08 Basic Rav 4 cyl. has an inconsistent problem with brake lock up! It`s not constant and only does it while driving! When they do lock, you can push the pedal and pull it back hard and they will release! It might happen again in the next few days, weeks, or even months! It has been Dealer checked with no problems found! The front rotors and pads have been replaced! It`s only got 58K miles! Any suggestions as to what`s causing this?:frown
 

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My `08 Basic Rav 4 cyl. has an inconsistent problem with brake lock up! It`s not constant and only does it while driving! When they do lock, you can push the pedal and pull it back hard and they will release! It might happen again in the next few days, weeks, or even months! It has been Dealer checked with no problems found! The front rotors and pads have been replaced! It`s only got 58K miles! Any suggestions as to what`s causing this?:frown
I'd take a close look at the master cylinder.
 

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Perhaps there is a problem with the brake antilock system? Are there any dash trouble lights showing when the brakes lock up, or otherwise?
 

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Discussion Starter #5
r4-brakes-lock-up

There are no lights anywhere! The brakes start to engage very slowly with very little pedal travel before fully engaged! I am handicapped with Peripheral Neuropathy in both legs and am unable to hook my toes under the pedal to release the brakes while driving!
 

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Have any modification been made to accommodate your handicap?
 

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I don't know if this is the same problem as you experienced but the other day I was driving my wife's 2012 Sport (4-cyl) and had to slam the brakes on hard due to some trouble ahead.

I avoided the car in front but the brakes didn't come off right away as I released the pedal . I was almost hit from behind by a large SUV which ended up beside me in the middle of the road.

My brake pedal has always had a lot of travel before any braking happens, not right at the top as you describe. A Toyota tech told me once that the computer senses how much braking you want from how hard you hit the pedal and applies extra the power that it thinks you need. Boy, I hate this nanny stuff.

This Toyota is the newest car we own but I've never had such trouble with any of the other cars we have or that we have owned. 40,000 miles on it and already on the second set of front rotors and pads. My '04 Xterra for instance has 90.000 miles and the original front pads are still over 50% and still on the original rotors.
 

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Discussion Starter #9
No that doesn't seem to be the problem! Luckily I`ve only had to lock-em-up once but they released immediately after releasing the pedal!
 

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My `08 Basic Rav 4 cyl. has an inconsistent problem with brake lock up! It`s not constant and only does it while driving! When they do lock, you can push the pedal and pull it back hard and they will release! It might happen again in the next few days, weeks, or even months! It has been Dealer checked with no problems found! The front rotors and pads have been replaced! It`s only got 58K miles! Any suggestions as to what`s causing this?:frown
some questions....
when you say "lock up" what do you mean by that?...are you going 60 and the brakes lock up leaving black skid marks on the road bringing you to a complete stop...
are the brakes locking up when you are lightly using them (like slowing down for a stop light)...
what are the weather conditions like when this happens (raining or just after driving thru water kind of stuff)...
to me brakes locking up means a complete stopping of the wheels and leaving rubber on the road til the rav is no longer moving...this would be very dangerous at highway speeds...
 

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Discussion Starter #11
I don't mean that kind of lock up! They start slowly engaging until they are totally locked! It can happen at any speed from 40 to 75 mph as that`s the limit for the roads I travel! I can tell when it`s happening because it starts to slow down and I have to keep giving it more gas to stay up with the traffic until I can find a safe spot to get off the road! Luckily it hasn't locked where I pose a traffic problem as most roads I travel have a wide enough median or berm that I can get off in/on!
 

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So you're driving along at 75 and then you start to feel the car slowing down...you then pull over...that is not locking up at all so now that we know what's going on let's get to it...
How long or far til the rav stops moving once the brakes start to apply?...my hunch is that one of your calipers is vapor locking or you have a rubber line that is collapsing...keep a bottle of water with a squirt cap on it in the car...the next time this happens try not to use the brake pedal to get pulled over...get out and squirt some water on each brake caliper and rotor...the one that is locking up will be hot as hell and will steam the water on contact...
 

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my hunch is that one of your calipers is vapor locking or you have a rubber line that is collapsing...
That sounded like the most likely cause to me as well, until I re-read the original symptoms.

When they do lock, you can push the pedal and pull it back hard and they will release!
Is the brake pedal returned to it's normal position by a spring, or does the master cylinder piston provide the pressure to return the pedal to normal? Is the piston rod connected to the pedal (i.e. locked to each other), or does the pedal just rest against the rod, and push the rod in when the pedal is pushed?

This is uncharted territory for me, I'm just looking for a reason to explain the OP's unique symptoms.
 

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That sounded like the most likely cause to me as well, until I re-read the original symptoms.



Is the brake pedal returned to it's normal position by a spring, or does the master cylinder piston provide the pressure to return the pedal to normal? Is the piston rod connected to the pedal (i.e. locked to each other), or does the pedal just rest against the rod, and push the rod in when the pedal is pushed?

This is uncharted territory for me, I'm just looking for a reason to explain the OP's unique symptoms.
I'm pretty sure the pedal returns using a spring...I'm thinking maybe the op pulls over and presses the brake and this sends pressure thru the lines and if it is some sort of collapsed or locked hose then maybe that pressure corrects it...if the op pulls over with minimal use of the pedal then if it is a single wheel position causing the problem they will be able to easily see what wheel it is using some water...
 

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Discussion Starter #15
I don't think that is the problem! The car may or may not travel very far before all the brakes lock! They`re all too hot to touch! It may travel 100ft. or 1/2 mile before they totally stop the car! It`s a very inconsistent thing!
 

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I don't think that is the problem! The car may or may not travel very far before all the brakes lock! They`re all too hot to touch! It may travel 100ft. or 1/2 mile before they totally stop the car! It`s a very inconsistent thing!
You should never touch brakes of a recently driven car...what I'm suggesting will tell you if 1 or more of the brakes are working harder than the others...like I said let the car come to a complete stop and spray the brakes with water...if 1 or 2 steam up more and or faster than the others then you have a direction to go it...however in the 20 plus years I have been working on cars I have never ever had a situation where all 4 wheels had equal brake application with no driver input...I have had several situations where 1 or 2 would...
 

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also look for any dash lights...it is possible that the abs or traction control system could be causing the problem in all 4 are getting equal brake pressure...
 

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When they do lock, you can push the pedal and pull it back hard and they will release!

  1. When you push the pedal down, will it not rise back to it's normal position by itself without pulling it back?
  2. When you pull back (I'm assuming upwards) hard on the pedal, how far does it travel above it's resting point?
  3. Do you feel any resistance or friction when you pull it back?
  4. When you are done pulling is the pedal further from the floor than when you started?
 
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