04 4Runner - Buzzing in Brake Pedal

I while back I had the dealer replace my brake booster assembly because whenever it started to charge back up I could feel a pronounced vibration in the brake pedal.
The vibration went away for a while but now it's back and it's worse. It feels like the anti-lock brakes are going off every third or fourth time I depress the pedal.
I have noticed that the brake pedal is very sensitive to any vibration in the truck. I even feel a slight bump in the pedal if I tap the steering wheel.
This is extremely distracting in stop and go traffic and sometimes dangerous because my first reaction is to ease off the brake whenever the buzzing starts in the pedal.
Has anyone else felt this? If so have you been able to repair it?

The obvious cause is that the brake booster cannister vibrates up against the bracket assemble that holds it in place.

I am hesitant to go back to my Toyota dealer until I have a list of possible solutions to the problem.

have you found anything else out? i was intending to take to the dealer to have it looked at. sounds like this may be a bulletin at some point. please let me know what you find out and i'll do the same.

Nothing yet. I have not had the time to bring it back to the dealer.
I suspect they will not be very helpful since they have already replaced an $1800.00 part.
It seems to me that the fix would be to replace the rubber stoppers on the brake booster cannister with some type of shock absorbing foam.
Please let me know if you make any headway on this.

i think i read somewhere in your other posts that you hear a clicking noise when you depress the brake pedal - did anything the dealer do fix that problem?

The problem first developed as a thump on the brake pedal. Whenever the cannister hit the bracket it could be felt on the pedal.
The dealership changed out the brake booster cannister and now it thumps and vibrates which is even more annoying.
Toyota really dropped the ball on this one.
I am almost at my 5000 mile oil change so I plan on taking up this (as well a a rattle in the driver's side door) with the Toyota dealer at that time.

Well I thought I would post an update to my ongoing buzzing brake saga.
As predicted the dealer was no help at all. Their master mechanic took my truck for a test drive around the block and told me he did not feel it. After threatening to take my business elsewhere he agreed to look into it.
After keeping the car for the entire day he told me that this seems to be the way that the truck was designed and that I would have to live with it. He then gave me Toyota's 1-800 customer care number.
I called them and they told me that someone would get back to me within three business days.
I have to say that this is my first Toyota and so far I have gotten nothing but runaround from the dealer and service center. They trivialize every problem that I bring up to them and they don't seem to have a very good understanding of their products.
Perhaps being an Engineer myself I don't suffer incompetence very well.
In any case I would encourage anyone who has felt this buzzing in the brakes whenever the brake booster recharges to call Toyota's customer care line and report the problem (1-800-331-4331).
If they get enough requests they may look into it and I would like to avoid having to go lemon law with this.

Dealers range from quite good to very poor in quality and helpfulness. Try another one if you can.

The master cylinder assembly has to be replaced to fix the problem. Toyota knows about this problem but it's an expensive fix so they play dumb as long as they can.

Do a search at the many 4runner forums on "buzzing in brake pedal" and print out the info for you're service manager to look at.

Mine was replaced about 9 months ago.

Well once again Toyota has managed to disappoint me.
I brought my truck in for servicing and demonstrated the problem.
The dealer brought in a Toyota factory tech to take a look. They kept my truck for 5 days and in the end told me that this is normal for all of their vehicles that use a nitrogen-filled canister in the brake booster assembly.
The factory tech, who refused to speak to me directly by the way (Toyota policy), made it known that there is no fix for this and there will never be a fix for this. Apparently I am the only person in the world that has complained about this and they don’t think that it is a big enough problem to waste any more of their time.
The dealer even refused to put any of this in writing.
On top of this brake problem the truck has developed a few loud rattles in the driver’s side door and there is very loud wind noise coming from the passenger side door.
Both of the problems were apparently “fixed” by my dealer and yet they remain.
I am so sick of this. It’s such a waste of my time.
They should change the truck’s name to the Toyota 4Runaround.

I have had similar problems with other brands also. This dismissal is not confined to Toyota.

(What? Me Worry?)

Hi all,

I know it's been like 4 years since the last post to this thread, but I was hoping someone might still be getting emails about this thread. I have a 2004 4runner with the buzzing/vibration and want to know what ultimately came about with you guys...if you still have it or not. Here's what I wrote in a new thread:

I own a 2004 4runner. There is a soft buzzing noise from under the hood and a vibration in the brake pedal every 4th time I press on the brake. I already had the master cylinder replaced (as others have mentioned in there posts), but while there were some stark improvements in the braking quality and the buzzing/vibration is much softer, it is still there. I know the noise is there because the truck has a hydraulic brake system that needs to re-pump itself after several pumps. However, I know that many cars/trucks have a hydraulic pump that do not make a buzzing or vibration. I was at a Toyota Service Center and I asked the mechanic to test another 4runner to see if it made the noise...all he had was a 2006 and it did not make any noise/vibration. He said the newer ones have updated systems. My problem is that I've read in another post that someone drove a 2004 4runner with NO buzzing/vibration. If this is the case, then there must be something that can be done to stop it in other 2004 4runners such as mine. Since the braking quality is good and the buzzing/vibration is much softer with the new master cylinder, I am going to try and live with it rather than waste time at the dealership to try and fix it. I understand it is normal and safe, but it is still annoying and want to know if anyone with the same model/year does NOT experience the buzzing/vibration AT ALL. I would appreciate anyone's input on whether you have the buzzing/vibration or not, so that I can get a gauge of how common it is. Thanks!

I've deleted the duplicate post to consolidate the threads into one. Though resurrecting old threads is generally frowned upon, new posts that help to close out open queries are welcomed.

That being said, an electronic type buzzing leads me to believe that the problem lies in wither the ABS system, the combination valve, and/or the master cylinder. If the ABS thinks the truck is braking to the point of lock-up you'll feel it kick in. Try this: get the truck up to normal speed with no other cars behind you and brake hard enough to intentionally engage the ABS, such as for a stop sign. You should be able to feel it through the pedal. If the sensation is similar, then I'd suspect a faulty ABS sensor, air in the ABS control module, or a defective combination valve.

There is no need for the hydraulic brakes to "pump themselves up". There is only a vacuum-operated brake booster to assist in braking (that big, round object that the master cylinder is bolted to). The hydraulic system itself is not pressurized...until you step on the pedal that is. Hope this helps!