My 04 coupe has 60k and has been making this weird grinding noise when I'm at around 40mph. I could feel the vibration from the grinding on the gas pedal, steering wheel, center console and dashboard. The vibration is less severe when I'm driving faster or slower. It does NOT occur when I'm braking so it's hard to figure out the root cause. Had 3 different mechanics told me that wheel bearings may be the cause and I replaced the one they all said was likely to be worst (front driver). This resulted in a smoother ride at lower speeds but the grinding did not improve at all. I'm not getting any good clues at all except tire pressure light comes on for no reason every now and then and I confirmed that all tires had good pressure. Anyone here had this issue?

 

Grinding noises, not good! Find a brake/alignment shop in your area have them check out your suspension and brakes...quickly! There's a gazillion issues that will cause a grinding sound, none of them are good...Gary

 

Is it a whining/humming noise? Could be wheel bearings.

Noise that gets louder/changes as speed increases is very indicative of wheel bearing failure.

I see you replaced the front driver one. Checked the rear bearings already?

I vote wheel bearing issue, or brake related, since you mention it goes away when braking. Perhaps if its not the bearings, it could be the brakes, and when you push the brakes, the motion of the calipers move the grinding piece a few mm away to where it doesn't grind. And returns to grinding when you go off the brake.

 

Graycar any luck with this issue? My 04 coupe is also having a slight grinding issue, but more prevalent when I brake. My TPMS light is also randomly coming on and off. I am going to my shop tomorrow to pull the TPMS codes and also do a wheel bearing check as well as a brake and suspension check. Wondering if there was any good pointers out there. I'll post further if I find something.

UPDATE: I used a Snap-On Verus and pulled the code for the TPMS. I found that one of the sensors had a low battery which is why it would intermittantly come on. I replaced the sensor and no more TPMS light.

 

Wheel bearing...or brake issue.

These cars are notorius for seized rear calipers. The sit low on the rear wheels and moisture accumulates in the lower slide pin eventually siezing it. The caliper is locked in place and only the piston can push the inner pad against the rotor. The outer pad looks fine, and so does the outer rotor, but the inner pad wears down to the backing plate which then contacts the rotor. When this happens, it feels like a grinding motion.

This goes undetected because the visible part of the rotor looks normal, so everyone assumes their brakes are fine.

Inspect the insider part of the rotor for roughness and grooves like this


If you find this sort of wear on one side, then more than likely the caliper side pins have seized.

 

I replaced three of my calipers (two front and one rear) on my 06 about a month or two ago. The passenger front pistons were seizing, driver side looked pretty bad as well, and the rear had seized caliper pins.

I had really bad car shakes in the same exact places you described. My steering wheel would shake to the point it hurt my hands to keep a hold if it. The console would shake all down the middle, shifter would shake, and I could it feel it in the drivers seat. I did the following and my car ride is smooth as can be now.

Check/replace calipers
Replaced my hub centric rings

I noticed an immediate difference after the those two fixes. I also did the following as well:

Lower ball joints
Front and rear Struts
Both lower control arms

I've a had wheel bearing go out as well last year in the driver's rear I believe and it's an extremely loud grinding noise. It sounded like I was dragging my muffler around on the ground behind me and it was only noticeable at low speeds. I don't remember it causing any shaking though.

 

Update: replaced both wheel bearing + hub assemblies up front and the horrible noise went away completely. that was about 3 months ago. Now I just replaced all struts and shocks along with their mounts and even replaced the shock bolts and bushings. drove fine for a couple of days. this morning I started hearing what sounded like driving with flat tires. The noise is different than before (no vibration or grinding and isn't as loud). I have to keep the speed relatively slow to be able to hear it; otherwise the road noise will drown it out. I searched around youtube and some ppl did have the same noise that they think is bearing-related. My mechanic told me before that my LCA is shot and should be replaced. He's not available to look into this yet and I'm not sure what is the source of this noise. Anyone with thoughts on this please share.

 

Found a video of a noise similar to what I'm hearing.

 

That doesn't sound like the seized caliper problem to me. (I had it a few years ago too on an '04 G35x.)
Although, after I got that fixed, I had another grinding noise which turned out to be part of a the shield near the rotors. Bend it a little back into place and problem solved!

 

That may be wheel bearings.

They are tough to feel unless you pull the rotors off. I know this is a lot of work, but spinning the rotor tends to mask the rough feel of a bad wheel bearing.

I've replaced 3 bad wheel bearings on my car and with the rotors on, you couldn't feel the roughness. Only when i took the caliper and rotor off, and grabbed the hub and spun it could you feel that it was bad.

I've had two fail at a time so that replacing one helped some of the roughness, but it was never truely gone until i discovered that my other front bearing was bad.

These cars are NOTORIOUS for bad wheel bearings (i've replaced 3) so I would suspect any sort of roughness to a failing bearing or two.