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We purchased our Rav4 new in December 2016. May 15, while in stopped traffic on I-96, there where 3 instances of pressing the brake pedal and nothing happening. The brake pedal went straight to the floor with no resistance and the car did not slow. Releasing and pressing the brake again stopped the car. The problem repeated on May 28 while driving about 25 mph and coming to a stoplight. It has been at 2 different dealers since June 9th, neither of which can duplicate the problem. The toyota regional tech can't figure it out either. I've been on the phone with the corporate guy, who is extremely difficult to get a hold of and not much help.

2 main purposes for this post: 1) to see if anyone has had similar problems and 2) if they did, was it able to get resolved? If so, how?

Toyota does not do any repairs unless they can witness/duplicate the problem themselves.

I reported it to NHTSA and discovered others have had similar problems.

I hope the vehicle is repaired soon because we like the Rav4 a lot (we have a 2008 too.) If it gets to 30 days at the dealer likely will seek a replacement under the lemon law. It's been a real hassle.
 

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Usually that situation is due to a fault in the master cylinder, or less likely a leak somewhere in the braking system. Has the dealer had the vehicle up on a lift to check for leaking fluid anywhere, including the wheels? Has the brake fluid level in the master cylinder been OK, or has the dealer been adding fluid?
 

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Wouldn't master cylinder failure have more consistent effect on breaks? Just thinking out loud. Reason I mention ABS, had similar thing happened to a friend few years back, different vehicle. he was unlucky tough.. rear ended someone :( and had a hard time proving that it was break issue
 

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I had that problem with another vehicle. Brakes would work intermittently. The cause was the master cylinder which sometimes worked as it should and sometimes didn't - depended upon whether the piston sealed or not. Apparently the seal had hardened somewhat and sometimes would not seal properly. Got a rebuild kit and that cured the problem.
 
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Good point, definitely a possibility. And "The toyota regional tech can't figure it out either" Hopefully someone will.
 

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I would say its a brake booster/master cylinder issue. I would hope they would check that and change it out for you. I would not drive it anymore and leave it at Toyota till they fix it and they should give you a loaner--I would defiantly escalate this issue with the Head man at the dealership. NO WAY I would just keep driving it cause it could end very bad.

I have an 08 GX and mine went bad at 72K--the booster and master cylinder in mine are all one unit, yours could be the same....
 

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Discussion Starter #8
There are no fluid leaks. Until toyota witnesses it themselves, their is nothing they will do. We are not driving the vehicle and it continues to stay at the dealer. I agree with the other posts - something odd likely with the master cylinder or ABS/VSC module.

We drove around with it last night with a service manager and the problem did not surface. It only occurs once every 500-1000 miles, still too often for my comfort level.

I told the service manager about the other similar NHTSA reports and suggested he reach out to the other dealers that have customers with similar problems. He blew the idea off and says the toyota tech experts would put out an alert if something was up.

No lights or codes register on the computer when it occurs. Is the ABS/VSC module talk via CAN? Presumably there is a heatbeat signal that the computer reads to know if it momentarily loses power and goes through a reboot, or if the processor gets lost. Maybe not though.
 

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May 15, while in stopped traffic on I-96, there where 3 instances of pressing the brake pedal and nothing happening. The brake pedal went straight to the floor with no resistance and the car did not slow. The problem repeated on May 28 while driving about 25 mph and coming to a stoplight.
I will make the assumption that there there are no visible leaks, and no loss of fluid in the master cylinder, because surely those would be the first things checked by the dealer.

A pedal going to the floor would never occur for any type of electrical or computer malfunction. The brake system is a closed system. Therefore you can rule out anything to do with the ABS electronic and mechanical systems.

My first suspicion is that the problem is that master cylinder piston is not sealing properly. I once damaged the seal on my MC piston and had similar symptoms (my problem was continuous though). The damage occurred after replacing my brake pads and pushing the brake pedal down further than it's normal travel, while I was resetting the caliper pistons against the new pads.

A second possible cause is boiling brake fluid in a caliper. If you were driving in stop & go traffic when the problem occurred, you might consider this possibility. If your RAV seems to pull to one side you may also have a sticking caliper which will also cause heat buildup and may cause the fluid to boil. Boiling can occur at lower than normal temperatures if the brake fluid is old and has absorbed some water. What consistently is the fluid in the MC, is it clear or does it look dirty and cloudy? Is there any sediment sitting on the bottom that may have damaged the seals?

Will your brake pedal slowly sink if you apply pressure and hold it for 30 seconds? What about making a very fast hard jab at the pedal, in comparison to the normal gentle pressure in everyday driving?
 

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The car is at the dealer so I can't examine the fluid. Since it was brand new in December 2016 I can only presume the fluid is clear and there is no sediment. Certainly something could be up with the MC. The pedal feels a lot better than our 2008 Rav, which always had a soft pedal from the first day.

I'm curious how the ABS and VSC work - to help regain stability of the car, there must be something that overrides the brake pressure to let a wheel spin even if the brake is applied.
 

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I'm curious how the ABS and VSC work - to help regain stability of the car, there must be something that overrides the brake pressure to let a wheel spin even if the brake is applied.
This YouTube video does a good job at explaining ABS. You can see that the hydraulic system is closed. The ABS motor simply blocks pressure from getting to individual wheels when the computer determines that the wheel is locked up.

If the valves in the ABS motor were to be stuck in the open position, then the car would operate like a car without ABS. Keep in mind that these valves should be fully open under normal driving conditions. This condition would not allow the pedal to sink to the floor.

If the valves were to be stuck in the closed position, then no pressure would reach the wheels and the vehicle would not be able to stop, but the pedal would be even firmer and harder than normal because the pressure from your foot would have nowhere to travel. Normally the pedal will drop an inch as fluid is pushed into the various brake cylinders on the wheels.

Vehicle Stability Control, simply uses the ABS hydraulic pump to apply the hydraulic pressure automatically (rather than you using your foot) and the same valves used by the ABS system determine which wheel(s) get the pressure.

So as mentioned in the earlier post, a problem with ABS or VSC would not cause the pedal to sink.

 

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He mentions there is a "supply and return line" to the master cylinder in the video. Wouldn't they both be supply lines, one for the front brakes and one for the rear brakes?
 

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He mentions there is a "supply and return line" to the master cylinder in the video. Wouldn't they both be supply lines, one for the front brakes and one for the rear brakes?
You are correct, I didn't catch that the first time I watched the video.

There was a thread regarding this subject a short time ago. The master cylinder has two separate chambers so that if the fluid in one chamber leaks out (due to a ruptured hose for example), fluid will remain in the other chamber to operate the remaining pair of wheels. In the past the divider for these 2 chambers went all the way from the bottom of the MC to the reservoir cap. In the RAV4 the reservoir only goes up part way, and may not be visible when the reservoir is full of fluid.
 

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Toyota was no help with the brake problems. I contacted a lemon law attorney, and she said that since the problem couldn't be duplicated, it would be a difficult case to win. So I went and replaced the master cylinder myself (with a genuine Toyota replacement). Today I took the old master cylinder apart. The first part of the bore has unusual machine marks. There are 3 "gouges" spaced 120 degrees apart that extend about 1" down the bore. I can't help but wonder if these gouges extend slightly into the groove of the seal, and every once in a while fluid blows past the seal and the brakes fail. Or are these marks intentional? Has anybody ever seen anything like this?
 

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Those gouges don't look like they have been put there for any functional purpose. They look like they are totally random, and they are what I would expect to be the cause of your problem.

I once damaged my own master cylinder after performing a simple pad replacement. As you know, after replacing a set of pads (and pushing the caliper piston back into the bore) it is normal for that first push on the brake pedal to sink almost to the floor. I think that extra long piston travel caused the damage in my case. Since then I am careful to only push the pedal the normal amount of travel several times until the pedal gets firm again.

Do those 3 marks match up with anything on the piston?
 

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It's hard to tell from the pictures, but the marks are definitely from a milling machining operation and not from assembly. My guess is a circular mill was used to cut the grooves for the seals, and somebody had a tool offset or program set wrong. The piston is a tube-like part with a cap and spring, and nothing has a mating feature.
 

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Those look like chatter marks from the boring/finishing machine - tool apparently was not securely mounted or inserted, or had too small diameter for the job. Those marks likely would have caused accelerated piston seal wear for the part of the piston area which contacts them. Not only apparently a machining error but also QA should have caught it, especially in such a critical system as car braking.
 

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We purchased our Rav4 new in December 2016. May 15, while in stopped traffic on I-96, there where 3 instances of pressing the brake pedal and nothing happening. The brake pedal went straight to the floor with no resistance and the car did not slow. Releasing and pressing the brake again stopped the car. The problem repeated on May 28 while driving about 25 mph and coming to a stoplight. It has been at 2 different dealers since June 9th, neither of which can duplicate the problem. The toyota regional tech can't figure it out either. I've been on the phone with the corporate guy, who is extremely difficult to get a hold of and not much help.

2 main purposes for this post: 1) to see if anyone has had similar problems and 2) if they did, was it able to get resolved? If so, how?

Toyota does not do any repairs unless they can witness/duplicate the problem themselves.

I reported it to NHTSA and discovered others have had similar problems.

I hope the vehicle is repaired soon because we like the Rav4 a lot (we have a 2008 too.) If it gets to 30 days at the dealer likely will seek a replacement under the lemon law. It's been a real hassle.
I have a 2017 Toyota RAV4 Platinum model I purchased new in December 2016. On July 13, 2017 I was at a fast food drive through and my service brakes worked correctly the first time in the line at the drive through. The second time the line moved the vehicle moved in front of me I lifted my foot off the brake and the vehicle stopped and I pressed the brake and had to press further down on the peddle to get my RAV4 to stop and during this waiting time my RAV4 started to roll forward and had to press even further down on the service brake. The line moved and when the vehicle stopped in front of me I pressed the brake and the brake peddle went to the floor and I did not stop until I hit the vehicle in front of me. I had the brakes checked the next morning July 14, 2017 at Massey Toyota in Kinston, NC. No paper work was filled out by the service department and no paper work was giving to me that afternoon when I went to pick up my RAV4. I just checked and no service on Toyota web site and no service has been recorded for July 14, 2017. My brake system has been adjusted on July 14, 2017 at Massey Toyota in Kinston, NC. I think my master cylinder has been replaced and a cover up has occurred so to avoid accountability for my brake failure. My damage was $577.00 and the other vehicle $485.00. REMEMBER was once in the DARK has COME into the LIGHT. I have seen on the National Highway Safety Administration complainant list a total of five 2017 RAV4 with brake failure and mine makes number six.
 

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I had the brakes checked the next morning July 14, 2017 at Massey Toyota in Kinston, NC. No paper work was filled out by the service department and no paper work was giving to me that afternoon when I went to pick up my RAV4. I just checked and no service on Toyota web site and no service has been recorded for July 14, 2017. My brake system has been adjusted on July 14, 2017 at Massey Toyota in Kinston, NC. I think my master cylinder has been replaced and a cover up has occurred so to avoid accountability for my brake failure. My damage was $577.00 and the other vehicle $485.00. REMEMBER was once in the DARK has COME into the LIGHT. I have seen on the National Highway Safety Administration complainant list a total of five 2017 RAV4 with brake failure and mine makes number six.
You need to call Toyota customer service and inform them about this "secret" repair. You would think after paying a 1.2 billion dollar fine for concealing safety defects, Toyota would be very interested in what your dealer did or didn't do. Plus they owe you for the damage to your car and the car you hit.
 

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One day after reading this post/thread my wife came to me after I brought up letting me know ANY issues with her 2014 Rav4 that I put all new rotors and pads on a good month ago.

http://www.rav4world.com/forums/126-4-4-mechanical/263465-2013-rav4-quality-coated-ebc-brake-kit.html

I owned a small hobby Audi repair shop years ago and have done about 75-100 brake jobs in my life. She came to me and said she had to do a panic stop and her Rav4's pedal went more to the floor and it did not brake like she thought it should, and her braking distance was longer because of it. It felt abnormal and scared the crap out of her. I asked if the ABS engaged and she said no and it was on the newer raked hwy concrete and she had a good dry road. She wanted me to go drive it and check it out. I said I don't need to. You just gave me all the info I needed to change out the master cylinder. If it was my car I may wait till I saw it again, but after looking at Rickl's post it's getting changed out ASAP. Five minutes after we talked about it, a new OEM master cylinder was ordered from one of those brick and mortar dealers that have an online store.....so I know I am getting OEM. I never and will never order a repair kit for a master cylinder. It is just too important of a piece in the brake system to play with for me. Now that they are all made of aluminum they get trashed by normal use let alone issue like Rickl posted from what appears to be an issue I have never seen in all the brake jobs I have done. Not saying that we know that is the problem and it happened that way but it is plausible. I will put a block of wood behind the brake pedal and floor when I bleed the brakes to reduce the brake pedal throw distance so if that is what is happening with these master cylinders, it won't happen again.

I am glad I saw this post, it lead me to what I think is a fast good decision that I might not of taken if I did not see it. Thanks for posting it


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