Hey everyone. For some reason, anytime I am on certain steep mountain roads in the Catskill Mountains, I get an intermittent metallic scraping sound that increases in frequency with vehicle speed and only happens when the brakes heat up and I release the brake. It stops when I hit the brakes. I can hear it out the driver window, but I can't tell which wheel it is. I thought it was the left front. As I would continue down the mountain, it would begin doing it when the brakes were on to slow down. As soon as I could pull over and let them cool for a minute and go again, it stops doing it completely. I actually got out of the car and felt the brakes. They were hotter than usual (like after a stop from 60mph) as I expected, but not on fire, smoking or hot enough to burn by just being near the wheel like when I had a stuck caliper a year ago. I had the brakes on both axles inspected several times and they could not find anything wrong at all. All pads are in great shape (checked by the mechanic the proper way, and by me by looking through the wheel. They looked fine.).

I did get a new IR thermometer yesterday and I took the brake temps after a stop from 55mph. The fronts were close (around 160-180F), but the rears were not. The left one was 140F on the braking surface and the right was 210F. The right rear has the oldest rotor on the car since the fronts were done last summer and the left rear was replaced last May when I had a caliper fail. The right rear wheel had the caliper stick after the brakes were replaced when the left rear caliper was replaced when that caused 2 brake failures. The only other anomaly with the right rear wheel is that it has a light score mark on the outside and some scratching from a rust hole about 3" wide in the backing plate. Could I be looking at a new rotor on that wheel soon? Or could that elevated temp be from the exhaust behind the wheel (stock, unmodified OEM exhaust).

Edit: I changed my decent route through the mountains to only use more major roads rated for faster speeds with less curves and shallower slopes so I don't have to use the brakes as much and I don't have that problem at all. The problem only happens when I ride the brakes on the more remote roads that have steep slopes and sharp curves to brake for. It does not happen on the highways even braking from high speeds to a stop.

 

Since the rear right rotor is showing signs of light scoring on the outside of the rotor and scratches on the inside from the backing plate hole and it is the hottest rotor on the truck, should I assume that the rotor is warping and hitting the brake pads when it heats up and causing all this? At 2-2.5 years old, it is the oldest rotor on this truck. All the others were replaced last summer. Maybe I should be having this rotor turned? Last May, the caliper on that wheel failed and got stuck. This was two days after the caliper on the opposite wheel failed twice in one weekend and took out the brake system. That caliper and rotor was replaced. When the mechanic put new pads on the rear axle, this caliper overheated. Made it hot enough to burn my leg from a foot away when I walked by the truck.

EDIT: Could the exhaust system have anything to do with the higher rotor temperatures? It is stock.

 

Bueller? Bueller? Bueller?

Bump!

 

I had the brakes checked out a month ago and there were no anomalies/problems other than the rear pads: The left rear was at 50% and the right rear was at 25% (which actually stops between 30-60F hotter than the other rear brake, but not burning or anything). The guy was surprised when I said there was only 16k on those brakes at the time. The calipers are not sticking or anything. But now I have another related issue. In town, those brakes are fine and are showing about the same temperatures (IR thermometer to rotor braking surface), but when I get back to my apartment and back it up down a steep hill (in neutral because it is steep enough to overpower the brakes if both the engine and gravity are fighting the brakes), I hear a faint scratching noise when I apply the brake. I checked the pads through the wheel and they look fine and seem like they have alot left, but what else could it be? 3 mechanics said between 1 and 2 months ago that the brakes were fine and one of them even said when I asked that he would drive this car to Florida.