I posted a topic about this a while back but it got lost in a sea of "more interesting" topics...

needless to say, I still have not figured out what is causing the problem.

The problem:

When I press the brake pedal (doesn't matter how hard or soft) there is a vibration under the hood which I cannot seem to locate. It sounds like it is coming from the firewall area or brake booster.. but when I listen under the hood, the noise is not audible. The noise goes away after a few seconds until the pedal is moved again.

It's very strange because nothing else creates the noise but touching the brake pedal or turning off my headlights after a drive (strange, right?). Nothing seems loose under the hood and I have not noticed a difference in braking performance.

If anyone knows what might be causing this vibration, please give me some insight.

 

Are you still under warrenty?

 

Warranty is going to expire in a few miles. I don't even know if I could make it to the dealer without going over 36k Lol.

Messed up, right?

 

sounds like you warped your front brake rotors

 

does it cause the wheel to go back and forth in your hands or is it some kinda of a ABS malcfuntion that is beyond our means of understanding

 

pioneer, funny you should mention that. I recently change my front brakes (last 1000 miles)... I would say problem solved, but my brakes work better than ever... Plus I think the noise was there before I had them changed.

AKAvensis, no the wheel doesn't go back and forth in my hands. The sound is only audible when the car is moving very slowly or at idle (otherwise the engine drowns it out). As for the ABS comment... maybe? The sound is similar to the one that ABS makes when it turns on... only not as extreme.

Oh and fyi: Yes, my brake fluid is at the right level.

Sigh. Lol.

 

my friend had a truck taht the ABS would come on when ever he hit the brakes no matter what, it would make a wierd clicking noise but wouldnt make the it stop or anything, ill bet its something with the ABS computer..

 

In that case, perhaps resetting the ecu might do some good. I've just about run out of ideas so I'm willing to try anything at this point.

 

tow it in if you have to have it looked at while its still under warranty. if it was brought in in the warranty period they have ta look at it. After that its out of there hands and you'll have to eat the cost.

 

The car is still under warranty until you pass the milage mark. As a part of that, the dealership has to pay for towing.

Call the dealership, I have seen other dealers allow for warranty work if its only a few (<10) miles over, especially if you tell them you are coming in. If they wont allow for that, ask for them to tow.

And if you have AAA Gold, call them and have the car towed to the dealer. Gold level allows for a tow of any distance (within reason, of course ). And it might be faster than getting the dealership's chosen towing service out there.

 

And if the dealer gives me the "Cannot duplicate problem so there must be nothing wrong" treatment?

 

but you said it happens every time? at least get it on record and to the dealership within the warrenty so you have some grounds to fight it if that happens.. threaten to call scion corporate and all that

 

It sounds like you are saying that it does it at idle/not moving as well, which means that the rotors are not the issue.

When you turn off the lights, you take some load off the alternator (And in turn, the engine). When you press the brake pedal, you also place a load on the engine (via the booster system). If anything is loose under the hood, chances are it is vibrating when the engine drops or raises in rpm slightly due to the small load changes. If you have a CAI, I would say it is rattling against the fender cutout. If you have a strut tie bar, you may have something rattling against it.

I would venture to say that if you turn the AC on or off while idling you will hear the same noise. Whatever it is, it is small, which is why you dont hear it over driving noise or higher rpm engine noise. It is also just enough of a vibration to be set off by the subtle vibrations caused when the load is changed slightly without much throttle involved.

 

As I expected, the dealer blew me off and literally said they "don't have the time to take apart my dashboard on saturdays". Of course, that is the only day I can bring in my car. Since then, my warranty has expired so I'm going to try and figure out what the problem is on my own... at least until I hear back from corporate Scion.

I have discovered that the vibration comes from behind the firewall behind and to the right of the gas pedal. The noise has also begun happening when I "blip" the throttle. Does anyone know what is behind this area that might cause a vibration?

I'm going to lift up the car tomorrow and try to see for myself what is making the noise.

Any other ideas?

 

dance around your car while swinging a chicken over the car. then take some feathers and brush it around the engine bay.

it worked for me.