Front-end metallic vibration noise - poorly lubricated brakes?

Question

I have a manual-transmission 2008 Mazda 3 I. For the past day or two, I have detected a somewhat quiet metallic vibration noise coming from the front-end of my car. Some things I have noted:

• The noise seems to increase when I turn sharply one way or the other.
• The nosie seems to increase when I take my foot off the gas - while accellerating, it is more or less gone.
• Pushing in the clutch or taking the car out of gear while moving seems to have no effect.
• Pressing on the brakes very lightly seems to slightly increase the noise.
• Braking harder (e.g. when slowing down to a full stop) seems to make the noise go away entirely.

Also, for what it's worth, my balance/alignment is good according to my mechanic a few weeks ago, and I have new (i.e., not warped) brake rotors. I also have not noticed any extra build-up of brake dust or smoke or a smell coming from my front brakes, so I don't think I have a caliper that's sticking.

I recently replaced my brake pads and rotors, and since taking the car out of gear not helping seems to imply that the noise isn't coming from the transmission, my brakes seem like the likely culprit.

Are these symptoms consistent with poorly lubricated brakes / brake calipers that aren't able to move freely?

Answer 1

The noise you are describing is likely the wear indicators on the brakes. They are small metal tabs that come in contact with the rotor when the pads nearly gone. It's designed to let you know that your brakes need to be changed. You mention that you just replaced your brakes, did you do all four wheels? It might be the lack of shims, or disc brake quite on the back of the pads but that noise is usually happens when you press the brakes, and goes away when you take your foot off the brakes

Answer 2

I've had very similar sounds from a bad wheel bearing before. For a 2008, that would be an early failure though. Not likely, but if you rule out the other items, check the wheel bearing play/feel.

Answer 3

You should have a look at the heat shields that cover the exhaust. The front lower shield is usually the first to break since it takes the mosts abuse. I'm picturing the one on your vehicle being held on by only 2 or 3 bolts (that are left) causing it to "tider-toder" while you are on and off the gas pedal. --> hard acceleration it would tilt to the rear of the vehicle --> hard braking would tilt it forward.

Before checking make sure that it's not too hot by waiting a few hours before getting close to it. Now, from standing in front of the front bumper and looking at the windshield get down on a knee and peak under the front. The exhaust comes down favoring the drivers side of the vehicle. The heat shield on the bottom will most likely be visabily damaged and if you were to give it a little tap you'll hear that metallic melody it's been singing you for the last however long.

Hope this helps.

Answer 4

I've resolved this problem by very thoroughly cleaning and lubricating my various brake components (a list of which components specifically can be found here), and by investing in a torque wrench to make sure all of my lug nuts are tightened evenly and to the correct torque.

Previously, I had just been using a crappy lug wrench that came with the car - had I known how much easier to use a torque wrench is, as well as how (relatively) inexpensive they are, I would have picked one up a long time ago.

I think the noise was most probably being caused by my lug nuts being tightened unevenly. The brakes being somewhat squeaky probably didn't help, and any vibration coming from the wheel was probably making the brakes make noise as well.