Ok, I know this has been covered just a few times already, but I feel like my case is maybe different? 2007 Saturn Outlook, just put new OEM coated rotors and O’Reilly ceramic pads on the front. Well, right after I did this the car started throwing a TCC transmission code on an unrelated issue, so it’s been sitting up, but is still driveable. Well I’ve been trying to run it once a week but have slacked a little and it has a good clean spot where the pads protected the rotor surfaces, but the rest of the rotor has some patchy streaks where I think there may have been rust that is getting combined with brake pad material. It scratches off with a scraper so I’m not really sure what I have. Just keep driving it, maybe a bit more often? I never got the chance to burnish the pads after I installed it before the transmission TCC solenoid code set.
Brake rotors are made of iron. Iron rusts.
Any coated rotor still needs bare iron for the brake pads to rub against. The coating just rubs away under the pads as it should, right away. Rust happens right then and there. Completely normal. The rust goes away next time you use the brakes.
Yes, what @Mustangman said is dead on accurate. Sometimes you will see the entire rotor get covered in what is called “flash rust” it happens from time to time when the conditions for it to occur are just right. If the vehicle is driven after this occurs, the rust simply rubs right off. If a rotor is left for a year lets say…sometimes that kind of rust never comes off and the rotor needs replacing. As long as you keep her moving the rust you see will not be a problem for you…
You know what they say… " A rolling rotor gathers no rust " and the somewhat less popular “A rolling rotor removes rust”
Lol! Say that three times fast! What mystifies me is the beautiful clean patch on the place where the pad was covering it, and the rest of the rotor has something on it that is probably pad material since it scrapes off so easy.
It protected the rotor from moisture in the air… so no rust!
Sometimes the opposite can occur where the pad promotes corrosion from moisture and the chemicals used to make the brake pad. It can form a hard spot that will eventually cause pulsation (sometimes identified as warped rotors). The industry term for it is “lot rot” because you see it on new cars left sitting in the new car lots for months.
I saw that on a vehicle I was considering on the lot. A newish Equinox, GM certified. Rotors looked like crap. If I had made that buy they were gonna have to change that junk. We got a 2018 Malibu LT instead. Hopefully this auto stop crap doesn’t wind up being a home mechanics nightmare. I assume the oil is much more critical in a stop start turbocharged engine.
I’d say that is the safest assumption! The turbo has very tight bearing clearances and high heat. Stop-start, I’d say it puts more stress on the oil. Oil is cheap and engines are expensive!
Few people and even fewer businesses would change rotors for that. A few hard stops often scrubs that off and it’s no big deal…
If you saw what I saw then maybe you’d change your tune. They weren’t rusty, they were scored up.
OK, the topic up to that point was rusty rotors and lot rot. You followed up by saying you saw that on a car on the dealer’s lot. You didn’t say they were scored. Yes, I would want that corrected however, I learned a long time ago not to let the seller correct certain things. I get cash compensation and do it myself. Goes for cars, homes whatever. The seller will do the cheapest job possible and you’ll be back there yourself shortly due to the cheap parts or lack of attention to detail…