After a good bit of driving, the noise reoccurred. I took it back to the mechanic and we decided it must be the brake pads. They're pretty worn out, and like I said before, they're worn unevenly. Since the problem is intermittent, perhaps the pads are making an awkward angle with the rotor sometimes, leading to the grinding/groaning noise.
I ordered new EBC Red Stuff (ceramic) pads and EBC USR (slotted) rotors. I had the shop install them today. So far so good - no noise - but we'll have to see what happens in a thousand or so miles once the pads are fully broken in.
I know I can answer my own question, BTW, but I'm going to wait until the pads are broken in before I conclude the answer to the problem.
I went to a well reviewed independent auto repair shop in my area. The first thing the mechanic brought up was that my rear brakes (the drums) needed to be adjusted. The mechanic showed me how my left drum was completely stuck, whereas my right drum was too loose. After he adjusted the drums, he told me to drive around for another couple hundred miles and see if the noise comes back.
Additionally, the mechanic mentioned that the drums could be the reason behind the uneven wear on my front pads. He also mentioned that the groove on my front rotor, although far from desired, is unlikely to be the cause of the problem.
Let's see what happens this week!
I have a 2012 Honda Civic LX. It's my first car, and I must say I drive it rather hard. After about 20k miles, my brakes started to feel wavy - I would hold the brake pedal, and the car would slow down in an inconsistent, wavy manner.
I figured that my rotors were warped (or, according to StopTech, pad material was transferred unevenly), and I wanted to learn more about my car's brakes, so I decided to replace my rotors and pads.
I bought new EBC rotors (OEM replacements) and pads (Ultimax2, OEM replacements), and I replaced the originals. I made sure I installed the EBC parts exactly the way the OEM parts were installed, and I was sure to check the brake fluid level and re-grease the caliper pins and pad brackets.
After I installed the EBC parts, the brakes felt orgasmic. With that said, I tried my best to avoid using them too roughly in order to follow EBC's break-in procedure (see EBC's FAQ, item #9). I followed the break-in procedure for about 500 miles or so before I slowly transitioned back into my previous driving style. Still, the brakes felt great.
After a few months, my brakes started to emit a terrible grinding/groaning noise when I braked sometimes. This part is important - my brakes do not create the noise consistently - only sometimes. When I don't hear (or feel) the noise, my brakes seem as amazing as they were after I installed them.
I was able to capture a recording of the sound after driving around for about 2 hours one night. I've uploaded the sound here.
Make sure you turn up your speakers so that you can hear it well. Every time you hear the noise, I was coming to a slow stop.
The noise does not appear at high speed stops or during throttle braking. It only appears at low speed stops.
With that said, it still only happens sometimes during low speed stops - other times, I'm able to come to a low speed stop with perfectly smooth, silent brakes.
The noise has never happened after a cold start (i.e. when I drive to work in the morning).
The noise seems to only happen after I drive around for a while. It seems to happen more often after I drive around for a while, then stop the car for a little bit. For example:
- Cold start
- Drive to XYZ
- Park for 15-30 mins
- Drive away
There's a good chance that the noise will occur during step 4, but no guarantee.
With that said, the noise does occur sometimes after driving around for a while without stopping at all.
The noise can come and go. For example, I could drive around for a while, start hearing the noise, then the noise might go away, and then it might start happening a couple of stops later.
This rules out surface rust, which would go away after the first couple of times of braking.
Sometimes, especially after the noise happens or before it's about to happen, I can hear a faint screeching/squeeling sound when I brake. I can only hear it when I roll my window down and practically stick my head out the window. This sound is very, very different from the grinding/groaning noise.
I do not notice any loss of performance in the brakes, even while the noise is occurring. The car slows down correctly.
The other weekend, I took apart my brakes to see if I could pinpoint any obvious problems. I also cleaned and re-greased all of the appropriate parts, although that did not help. Here are my observations when I took apart the brakes:
The pads are worn unevenly. The tops of the pads are visibly thinner than the bottoms of the pads.
The outer side of my driver's side rotor has an apparent groove on it:
The corresponding brake pad has a matching groove:
However, if this groove was the cause of the noise, wouldn't the noise happen every time I brake?
I tried to bed in the pads using the 60-10 x5 procedure (slow down from 60 MPH to 10 MPH several times with short cooling periods in between, also described on EBC's FAQ).
This did not help - the noise happened again the next day.
With that said, I'm not entirely sure if I performed the procedure correctly - perhaps I did not slow down quickly enough.
What's causing this terrible grinding/groaning noise when I use the brakes sometimes?