Faint buzz/pulse in brake pedal in breaking

Hello everybody, you have probably seen many post about my crazy anoying questions in my new truck.

Just want to make sure all is normal.

(when you come to a stop...about 5 seconds before the car comes to a complete stop do you feel a little buzz in the brake pedal.)

 

Hey I am having the same issue. I have a 2017 Tacoma TRD Off Road and have had it in the shop 2x. Today was the second time when they had a field technician come down to look at. The service tech called me and said the field tech verified it was normal and that all the TRD Off Road models will do this. It is the brake booster and very close to the firewall that seems to cause this. It does this every time I come to a stop at least 2 times per stop. I assumed they were going to find a fix for it today but came up with the same stuff they did last time. It is very annoying for sure, I have gotten a little used to it but it still bothers the crap out of me. I test drove 2 and do not recall it doing this on either one. When I left the lot though I noticed it, maybe it takes some time to go away. Anyways I just wanted to let you know I am experiencing the same problem you are.

 

I've gotten the same thing a little in a manual TRD OR DCSB, also have had the headlights and heater dim/drop intermittently when braking. Along with the 20mph and under rumble strip. Made the dealer aware of both issues, I plan on pushing the rumble strip at my 10k and if the headlight thing keeps up that too. The rumble strip is pretty consistent while the lights dimming has not been. I did experience the BUZZ once in my driveway playing with the brakes to see if the headlights would dim. Happy it wasn't the squeal sound one guy was having.

I also have experienced what seems like a hollow spot intermittently where its like "oh shit!" and there's no brake as I depress the pedal. Makes me wonder if the booster is kicking in or out of action.

Trying to ride it out, I'll keep posted here if anything changes.

 

Just got back from the dealer. I drove another trd oddroad and the vibration in my pedal is much worse the other truck I drove. The tech that came to look at my truck said it was normal and both trucks did it. I wouldn't have noticed the vibration in the truck I drove tonight if I weren't paying attention to it. I did get in a couple more trucks and started them pushed the pedal as hard as I could and got no vibration. Then drove one more and it was a little similar to mine. They are updating my case and the service manager said he is going to try everything he can to get it fixed.

Just thought I would post an update.

The truck is still great just a little frustrated this can't be fixed.

 

It's a brake booster. These trucks don't have normal master cylinders. They have motors attached to them and they build a reserve of pressure so that the truck can apply the brakes on its own either to help you in an emergency stop or to keep one of the wheels from spinning excessively.

What your feeling is the pump building up pressure because a sensor has detected that the pressure has decreased. That reserve pressure is used any time you brake so the motor will kick on intermittently as you drive to replenish the pressure.

The only bad part about the system is that it's ridiculously expensive to fix. When it fails it'll cost you about $2500 to replace. Toyota only sells them as complete units. Fortunately they're pretty durable. Most older 4Runners are still on the original unit at 300k miles.

Pop the hood and look at your master cylinder and you'll see what I'm talking about. Better yet, pop the hood, put your hand on the master cylinder and have someone else start the truck and pump the brakes.

 

don't have that but when slowing down from roughly 80km once I get around 30-40km I notice a sort of surge feeling.
kind of like a shuttering rumble. Not a rumble strip feeling though. Almost like a warped rotor feeling.

 

Yep the Off Road Booster/MC is a Electro/Hydraulic Unit that runs the ATRAC or Crawl Control System so it definitely has a funny feel to it.

 

I feel a single pulse/knock in the pedal under moderate braking pressure. It's a strange feeling but I wouldn't describe mine as a vibration.

I've been able to replicate when the truck is idle and stopped.

The feeling does not occur when the vehicle is off so I had assumed it was related to the braking systems used by MTS and CRAWL.

I too asked my Toyota service department to check it out and they said everything was fine.

I'll need to read up on the brake system in this truck to better understand. So this is a fluid pump that builds a reserve of brake fluid pressure?

Is there no vacuum-assisted brake booster?

I need to buy a FSM..

 

y'all are over thinking this, it's normal for that in the O/R

 

I don't think we are overthinking it. After driving a few different trucks yesterday there are different levels if the vibration in the brake pedal in the trucks. In my truck if it is started in park I can push the brake pedal down and it starts the booster everytime I do it. None of the trucks I got it or drove yesterday did this, and the vibration was so faint on the other trucks I would have never noticed it if I had not been looking for it. The service manager agreed the vibration in my brake pedal was much more pronounced than the other trucks. Personally I think there is something going on with booster in my truck, and they will not even try to replace or fix it unless there is a service bulletin. I could deal with this much better if it wasn't something I had to use every time I drive the truck, I can't just not use the brakes though

 

I've had it on mine but what is weird is that I've not been able to replicate it with consistency. It comes and goes it seems regardless of temp, time of day, weather, etc. I had it fairly pronounced for a few days and then it went away. I couldn't get it to do it again until a few weeks later it started up again.

 

I'd really like to tell you guys that it will get better with time, but that's not the case. My 2004 4Runner has the same system and the vibration isn't just a slight tingling in the pedal, it's actually audible. It's still functioning well at 150k miles and 13 years old but it's definitely more pronounced than the Tacoma.

To be fair, I don't know for a fact that it's the same part number and design. There might be minor differences between the two units that would account for the more pronounced vibration in the 4Runner but I have always just attributed it to the age of the system.

Everyone's tolerance for vibration is different so it's going to bother some people more than others. I am notoriously sensitive to any vibration or weird sound and for some reason this vibration just doesn't bother me.

 

Since the TRD OR brake booster is electric (not powered by manifold vacuum), the effect should be reproducible with key on engine off. In my 2nd gen, I can hear the pump run when I step on the pedal, but feel no vibration.

 

I don't remember but I think the pump is off with the ignition off, you have to have the keys in the 'on' position to bleed the breaks

 

^As I said, key in "ON" but engine not running.

 

So yeah, today I turned the radio and AC off and paid very close attention to it. Sure enough, it is indeed exactly what everyone else is describing. I feel a pulse when the pump kicks in, I can hear a VERY faint hum, and then I can feel the pump disengage about a second later.

Took a look under the hood and noticed the the lack of a vacuum assisted booster.

After reading all this info and seeing how the electric pump is used, it makes sense that the pump would spin up to build additional pressure when a moderate braking pressure is applied to make up for the lost pressure from the brake application.

Thanks a ton for the explanation guys, my mind is at ease now. The feel is annoying and unlike anything I've felt before but I guess it's just something you have to get used to

 

Anyone else experiencing the headlight/heater blower power fading/dimming when brakes are applied (happens intermittently). I had the dealer test the battery and the system checked out.

 

Did you add any aftermarket electronics, lights etc?

 

100% stock, no mods to anything electrical.

 

Yes, I do notice that my headlights dim when the brakes are applied. Notice it at idle/low rpm.

Not sure if there is much reason to bring it up with the dealer. But I may, to at least get it in the records.

I am all stock, no mods as well.