2023 Braking Issue

Greetings,

This is my first post, though I've browsed the forum on-and-off since purchasing our 4Runner back in 2023. I'm just not a big forum/social-media user. However this week we had a very odd issue with our truck which I could use some help with, so I thought I'd throw it out there. Apologies in advance for the wall of text.

The vehicle in question is a 2023 4Runner 40th Anniversary edition (white, if anyone cares). We purchased it new in February of 2023 from a dealer here in Western Oregon. It currently has about 28,000 miles on it. The vehicle is essentially bone stock... no mods, no aftermarket parts, still has the OEM tires and brakes and everything. I do my own maintenance which so far has consisted of oil changes and tire rotations... that's it. It's been to the dealer twice in 3 years; once for the second key fob, and once for new windshield wipers and a new cabin air filter. It's a pavement princess; never been off-roaded, seen very little snow or ice; lives in the garage out of the weather and away from the rodents. We've been very happy with it.

A little about me: I've been working on and around trucks and heavy equipment, on-and-off, since I was a teenager. I do most of my own maintenance, including on my Freightliner tractor and trailers (I have a Class A CDL). I'm not going to claim I'm the world's greatest mechanic but I know my way around machines and things with wheels. I've driven and worked on vehicles with no brakes, bad brakes, leaky brakes... you name it... and this has got to be one of the strangest things I've ever encountered.

On Friday I had to take my wife to an appointment. We got in the truck, started it, pulled out of the garage and into the driveway, which is a slight uphill to the street, so I basically just let it coast to a stop before I turned on our street. Turned left, up to about 20 MPH, then hang a right on the next street. I braked gently for the turn and thought gee, the brakes feel a bit mushy, but didn't really think much of it. Another 1/4 mile to a stop sign, start braking and... nothing. I pushed the pedal essentially all the way to the floor, and only at the very bottom (against the floor) did I get any braking force at all... damn near ran the stop sign. OK, something's not right. Accelerated to the next intersection (also slightly uphill) and as we got there, same thing... pedal to the floor, very little braking action. At this point it was like well, we're clearly not driving this the rest of the way, so I hung a right and went around the block back home. There were maybe 4 more residential intersections I had to brake for, same thing every time. Got home, backed it into the garage... still mushy in reverse. We took another vehicle to the appointment.

When I got home later I went out to look at the truck. Full of brake fluid, no leaks anywhere that I can see. It started normally, but when I stepped on the brake pedal to put it in gear, same thing... almost all the way to the floor... so I put it back in Park, pumped the brakes a few times (still running), same thing, very little resistance and all the way to the floor. I got a single warning on the dash at this time about the collision avoidance system, "please see dealer", and then the warning went away. I shut it off.

I called the dealer Saturday morning and got an appointment to bring it in later that morning, then called a local tow company to take it there. The driver never started it or used the brakes, just put it in neutral and winched from the garage up onto his tilt-deck. I followed him to the dealer and described to them what had happened. They called me yesterday afternoon and stated that they could find nothing wrong and the truck seemed to drive normally when they tested it. I told them, in not so many words, that there was no way I was driving the truck again until they had figured out what happened, what caused it, and how to fix it. We agreed to let them keep the truck for a while longer to keep trying to reproduce my issue. They're closed today so I assume I'll follow up with them tomorrow.

I've done a pretty thorough 'net search, including this and other forums, and only found a handful of references to this sort of issue on a 5th Gen 4Runner. A couple Reddit threads described it almost to a T but of course, there was little follow-up. I think one thread the OP came back and said "the dealer replaced the entire brake system" but that was about it.

So, questions: Has anyone ever experienced or heard of this sort of thing before? What was the cause and/or resolution? Has anyone ever had to escalate this kind of issue with the dealership, or higher than them to whatever powers-that-be at Toyota? I generally don't deal much with dealerships or their repair shops... though my typical approach to stuff like this is to let them have some time and space to solve problems their way, first. But I'm concerned about the writing on the wall here: that they're going to say they can't reproduce the issue, and therefore can't (won't) do anything about it.

Thanks for reading all this, I appreciate any insight any of you might have. I will check back and keep this thread updated as things progress.

 

Go to the dealer and have the service manager ride with you and see if it does it. If it's truly acting normal all they can do is fire the parts cannon.

 

Welcome

 

Why not ask them to do a complete brake bleed and add new fluid to see if it does it again. There has to be air entering the system.
Your vehicle is too new to have a failing master cylinder but it could also be possible.
Is it throwing any ABS codes?

 

What you describe is what I experienced with my 4th GEN which has much the same braking system if not exactly the same, what happened on my 4th GEN is the ABS/master cylinder assembly lost pressure that is provided by the small electric motor/pump/accumulator to assist the braking and provide pressure for the ABS system, this pressure is built up everytime you turn on the ignition and about every third depression of the brake pedal (if you listen closely you should be able to hear the motor running/buzzing from behind the instrument panel for about 15 seconds normally), usually the issue is with the electric motor wearing out and not being able to drive the pump, on mine when it failed there was an alarm, the brake warning light as well as the pedal going to the floor.

Many just replace the motor and that usually solves the issue, but just the motor cost around $500 to $700 but you can also get a rebuilt motor for around $300..but you have to remove the master cylinder assembly to replace the motor and reinstall it, my T4R is my daily driver and I didn't want to take the chance that the motor alone would solve the issue so I bought the entire ABS/master cylinder assembly for $1100(buy once cry once) and it works like new now.

You didn't mention the alarm/brake light so I'm not sure why you didn't get the alarm/light but otherwise your symptoms were exactly the same as mine.

The assembly has a ABS module on the side of it, it's possible it glitched and caused your issue by not allowing the motor to activate.

 

Thanks for all the responses so far.

AuSeeker, really appreciate the detail. Correct, no warnings or lights. Just taking a cursory glance at the system, I noticed the accumulator canister attached to the master cylinder and my first thought went there. As hydraulic systems go, brakes are fairly simple, with the primary input being your foot, so if your foot moves the piston in the master cylinder through its full travel (all the way to the floor in this case), the fluid has to displace "somewhere". And if it's not leaking outside, then "somewhere" has to be within the system.

Still a little shocked that anything should be failing or "glitching" on a vehicle this new. I'm also surprised that the system is even capable of failing in this way. Losing brake boost (vacuum, hydraulic or otherwise) is one thing; having a path for brake fluid to displace to that's internal to the system but provides little or no braking effort, is just strange.

 

I agree that yours is too new for this to be happening, and also that you shouldn't lose almost all braking, my advice since mine failed is to practice and be prepared to use the parking brake and downshifting to come to a stop if it ever happens to you!!

Using the parking brake takes some getting use too, because you have to press it again to release it, not like the old days parking brakes!!

 

I thought I would provide an update if anyone cares...

The dealer kept the truck for several days but was unable to reproduce the issue, driving it around the lot several times a day. They determined the single warning I saw, which was associated with a code, likely came from me rapidly pumping the brakes at some point. I ended up taking the truck home late last week, and it appeared to be operating normally. Put several hundred miles on it over the weekend with no change, until yesterday.

Yesterday towards the end of a 90-minute trip I observed symptoms similar to what I first saw. At highway speeds the brakes operated normally but at low speeds (20 mph and under) there was a gradual loss of braking, the longer I had the brakes applied. I also noticed that standing still, engine running and in gear with the brakes applied, the pedal would slowly sink to the floor, to the point where the brakes wouldn't hold the truck still against the torque converter. I was all ready to drive it straight to the dealer to show them, but I stopped/restarted the truck and... problem gone. However since then I've gotten it to reproduce one more time after about 8 starts.

This thread from 2020 comes the closest to describing what's going on: Brake Pedal Issues | Toyota 4Runner Forum [4Runners.com]

At this point I'm basically waiting for the issue to happen again so I can take it to the dealer and show them in-person what it's doing.

 

@234Runner40th
Suggest if at all possible, if/when this occurs again, start videoing asap to show your service writer or manager!
Vids go a long way helping explain your issues.

 

Thanks for the tip, I will try to get it on video next time it occurs.