The rear driver’s side disc brake of my 2012 Accent has a intermittent problem. The car has only seen two winters and has a little over 30,000 miles on it currently, and has been trouble-free otherwise, but the issue started late this spring and has been happening on and off for the last 5000 miles or so. I apologize in advance for the length of this post, I don’t have much hands on experience with issues like these but I am learning, and I probably included too much detail for fear of leaving something important out.
The outer rear brake pad seems to be sticking against the rotor, and at speeds above 30 mph it will sometimes cause a high pitched sound that I first thought was the wear tab or a stone stuck between the brake pad and rotor. The odd thing is the noise stops while turning either left or right, or while the rear brakes are being applied (tested this with the e-brake) and dies out once the car slows below 30 mph.
After hearing the noise back in the spring, I inspected the brakes on all four wheels, cleaned and lubed the sliding pins with synthetic silicon brake grease, removed the wear tabs to be certain they weren’t the cause, had it looked at shortly after during the last service/inspection and they found no obvious problem so I thought I had solved the problem for a while. However while feeling the rims and lug nuts after long drives over the past two months, the other 3 wheels are always cool and lug nuts are luke-warm at most to touch, but sometimes the rear drivers side wheel is warm and the lug nuts too hot to touch for more than a second or two. It doesn’t happen most of the time, and might not at all during a long trip, but then could happen later that day after driving 10 miles but wouldn’t give any other symptoms or effect fuel mileage.
Just this week, the high-pitched noise came back again, and upon inspection I discovered the brake pad on the outside was worn down to maybe 3mm of thickness while the other pad (against the piston) looked almost like new. The rotor seems fine, no sign of discolouration. The piston moved freely when I compressed it, I also bled some of the fluid out and it looked clean as well. The sliding pins didn’t feel stuck or seized and no rust anywhere but I cleaned and re-lubed them once again. I also cleaned the brake pads and metal clips with a wire brush but noticed they don’t seem to have much play in the retaining clips, I had to use a screwdriver to tap them out even after cleaning them. From what I’ve read since, this isn’t normal as the pads should move freely? Or this is this problem more likely because an issue with the caliper such as sticking slide pins?
Any thoughts or help would be greatly appreciated, thanks!