Brake ABS/Master cylinder assembly noise

[52577]

Just recently noticed after the 4R has been off for awhile, like overnight, the ABS brake master cylinder assembly makes a buzzzzz about 5 to 15 seconds (depending upon how long the 4R has been off), then a click and it stops. I verified it's coming from the master cylinder assembly by turning the ignition to the on position and quickly inspecting/listening.

It seems to be coming from the cylindrical accumulator pump motor seen in the pic below. Wondering why the accumulator needs to pressurize when 4R is has been off?

Is this normal operation?

Stats: 2004 SR5 V8 RWD, 33k odometer miles.

Thank you.

 

[52577]

Not my video but this the exact noise:

https://youtu.be/WhkUFugFXrw

Is this normal operation or sign of failure?

thanks

 

[Crave4runner]

Not my video but this the exact noise:

https://youtu.be/WhkUFugFXrw

Is this normal operation or sign of failure?

thanks

Following... i hear the same sound when I apply the brake petal.

 

[52577]

.


Note to self: When in doubt check the owners manual. (blush)

Brake System, Page 277:

"You may hear a small sound in the engine compartment after the engine is started or brake pedal is depressed repeatedly. This is a pump pulsating sound of the brake system, and it is not a malfunction."

Also Page 277:

"The brake system has 2 independent hydraulic circuits. If either circuit should fail the other will still work. However, your pedal will be harder to press and your stopping distance will increase. Also the brake system warning light may come on."

The owners manual is the T4R guide, but it confirms other posts I just found today indicating the pump sound upon startup is normal operation.

For my concern, I will call this case normal. The pump is an electric motor and like anything it could fail someday. It would be prudent to keep an eye on it and have the system checked out if the pump stays on constantly or the brakes feel abnormal.

Hope it helps others who are concerned.


.

 

[Pitbull410]

I've just noticed mine making a loud pulsating vibration for 5-15 seconds after start up. I never heard it before in my 5 years of ownership until just this winter. Could it but mine is going bad and needs replaced? Read in another thread it's not a cheap part...~$3k

 

[52577]

It depends upon how loud it is and how your brakes feel.

I've had my 4R for a few months now and first I didn't hear it. In my situation I had the 4R outside and would start it immediately. The 4R was running and outside so I nerver heard it due to the engine and outside noise.

I park the 4R in the garage now. I put the key in but this time turned it to the "on" position, something I never did before.

Because of the acoustics in the garage, everything echos and is amplified. I thought there was something wrong. Turning it to the "on" position outside it's not as noticeable.

This is my theory anyway for my situation.

From what I read online if going bad it will make a noticeable, almost grinding buzzer type of sound.

If it makes a steady buzzzzz, click, buzzzzz, click.. sound that is most likely normal.

 

[4Slow]

ABS noise

What year 4Runner are you hearing the noise. I have a 2018 TRD OR and just started hearing the noise. I hear the buzz from under the drivers side dash. The dealership told me this is normal. This is the 4 4Runner I have owned. The last was a 2015 but it never made this noise. Thanks