noise from underdash when applying brake
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TranceKrayz
New member
the hissing noise is normal......i don't know how to explain it though but it is. can someone else clarify?
sharp4runr
New member
TranceKrayz said:
Yes I've been told its normal from the dealership. Its apparently the brake master cylinder pumping the brake fluid.
I hear it on mine, but doesn't buzz in any way...
Mine does it too, if you brake repeatedly in a short period of time.
The power brake booster on the 4Runner is an electric pump, with a reservoir that maintains enough pressure for a couple of brake applications, after that the pump has to run and build the pressure back up.
This differs from some cars that use either the power steering pump or engine vacuum for the power brake booster. That is the reason why you don't hear this noise on many other vehicles.
I like the electric pump style booster, because that means that you will have power brakes, even when the engine isn't running, as long as the ignition is on.
It's nothing new though, my parents had a Pontiac station wagon back in 1986 that had the same type of system (yeah, it had wood-grain on the sides too.
: ) Unfortunately Pontiac didn't engineer the system very well, and it was a POS.
--Mike
The power brake booster on the 4Runner is an electric pump, with a reservoir that maintains enough pressure for a couple of brake applications, after that the pump has to run and build the pressure back up.
This differs from some cars that use either the power steering pump or engine vacuum for the power brake booster. That is the reason why you don't hear this noise on many other vehicles.
I like the electric pump style booster, because that means that you will have power brakes, even when the engine isn't running, as long as the ignition is on.
It's nothing new though, my parents had a Pontiac station wagon back in 1986 that had the same type of system (yeah, it had wood-grain on the sides too.
: ) Unfortunately Pontiac didn't engineer the system very well, and it was a POS.--Mike
I am having this problm, and it's getting kinda annoying. Is there any way to fix it? by replacing som part? Well of course if this booster is designed to work with such a noise, I will drop my expectation but if only some 4runners do and some don't, I am changing whatever it is that makes that noise. Any clue on this?
ironxman99
New member
i have a brand new 07 4runner and am experiencing the same thing. whenever i brake, there is a sort of light hissing/suction noise. is this normal or something i need to get checked out?
how many of yall have this hissing noise when applying brake
I am having this hissing noise every time applying the brake. There is nothing wrong with the brake but sometimes when it's quiet, it's kinda annoying. The toyota dealership (3 in a row) people told me this is normal, but I wouldn't believe that this truck is designed to work like this. So just want a stat of how many of you guys have this noise and how many don't. Any input is appreciated!
Mine is 2006 SR5 V6 4X2, and has 10k miles on it.
I am having this hissing noise every time applying the brake. There is nothing wrong with the brake but sometimes when it's quiet, it's kinda annoying. The toyota dealership (3 in a row) people told me this is normal, but I wouldn't believe that this truck is designed to work like this. So just want a stat of how many of you guys have this noise and how many don't. Any input is appreciated!
Mine is 2006 SR5 V6 4X2, and has 10k miles on it.
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I have a 2004 Sport Edition and I notice the hissing as well. I also notice a small amount of shaking when the brake pedal is pushed in all the way. It's not a worn pad/rotor type of shaking (I've felt that before). I was thinking that bleeding the lines may eliminate that, but if it's a system design issue, then I'm okay with it. I would like to know what the hissing is though.
sharp4runr
New member
It's normal to me, maybe the guy who doesn't hear it has bad hearing 
My 2004 has the same noise and my old 1993 Toyota Celica had the same noise. 3yrs and 34k and the brakes are as good as new...
My 2004 has the same noise and my old 1993 Toyota Celica had the same noise. 3yrs and 34k and the brakes are as good as new...
Well, mjfrank's explanation is good but still not making a lot of sense to me how this noise is generated. Only because of the electronic pump? Then how come some 4runners of the same make don't have this noise?
As I took my truck to toyota dealerships, i have conflicting/different explanations from them. One told me it's because of the space between the piston and the pedal, the other said it's the rubber that piston pushes, and Precision people said it's the sound of power brake fluid going through the line...so I am confused. Let's see we have
(1) master cylinder, which has piston(s) inside supposably pushing some rubber cups
(2) power booster, which as described by mjfrank, is a electronic pump
(3) power brake fluid line, in which fluid travels
Can anyone tell me specifically which is the one that makes the noise? And how? Or where I can find info about it? Toyota people have been reluctant to touch anything. I am trying to denoise by replacing or whatever.
As I took my truck to toyota dealerships, i have conflicting/different explanations from them. One told me it's because of the space between the piston and the pedal, the other said it's the rubber that piston pushes, and Precision people said it's the sound of power brake fluid going through the line...so I am confused. Let's see we have
(1) master cylinder, which has piston(s) inside supposably pushing some rubber cups
(2) power booster, which as described by mjfrank, is a electronic pump
(3) power brake fluid line, in which fluid travels
Can anyone tell me specifically which is the one that makes the noise? And how? Or where I can find info about it? Toyota people have been reluctant to touch anything. I am trying to denoise by replacing or whatever.
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Just back from a toyota dealership, once again. Tried two brand new 2007 4R. Both have this hissing. And the noise is from the newly designed booster, started from 2005. I still won't believe it but seems that it is designed to work with this noise. Okay, maybe really have to live with it.
brownersd
New member
Hello mates!
I experience the same issue. I talked to my dad about it, whom is a Master Tech, and he states that it is the EBD system. (Electronic Brake-Force Distribution) The 4Runner has a feature that monitors the position of the brake pedal, and determines how quickly you stomp on your brakes to make a "panic stop." There is a master cylinder that's normal, but in addition, there is an electric pump that keeps the lines "primed" so that extra force may be applied in emergency situations. With repeated brake applications, the pump kicks in to recharge the system. Hope that this helps.
I experience the same issue. I talked to my dad about it, whom is a Master Tech, and he states that it is the EBD system. (Electronic Brake-Force Distribution) The 4Runner has a feature that monitors the position of the brake pedal, and determines how quickly you stomp on your brakes to make a "panic stop." There is a master cylinder that's normal, but in addition, there is an electric pump that keeps the lines "primed" so that extra force may be applied in emergency situations. With repeated brake applications, the pump kicks in to recharge the system. Hope that this helps.
ron70062
New member
Boy , after reading this post , I feel semi better. Only thing is , Im reading about 03 and up making the noise..unless I missed something. Mine is a 2001. Im hoping thats what Ive been hearing. I thouht it might be coming from the power booster . To be on the safe side , Is there a way to test it so Ill know it's ok?
