Yesterday morning, as I backed out of my short driveway, I felt a grinding and then felt a thunk on the passenger side when I applied the brakes. Why would my new Venza[~5401 miles] have this? The dealer didn’t feel it during a drive and couldn’t find anything wrong with the brakes on inspection. The dealership claimed it was due to rust. I don’t buy it. Why would new brakes rust and why would Toyota make brakes that rust?
It can be due to rust, actually. Rotors and pads are not rustproofed (because that would be silly as braking is ablative and wears surfaces down, so any rust proofing you put on would get worn away when you used the brakes). So if the brakes get wet/damp and then sit for awhile, they can develop surface rust. It’s not a big deal because, just as the rust proofing would be, the rust is quickly worn away when you brake. This rust can form as quickly as overnight if weather conditions are right. It’s not at all uncommon to walk the lot at any dealership, even high-end cars like Lexus or Porsche, and see rust on the brake surfaces, because they haven’t been driven in awhile.
Sometimes that rust will lightly bind the pad to the rotor, and then when you first start moving in the morning, you feel a clunk and/or hear grinding as the rust bond is broken and then the rust is scraped off.
…or the OP may be merely hearing the ABS system going through its normal self-test.
This takes place on a cold start, after driving…perhaps 10 ft to 30 ft.
If the noise takes place only under the circumstances listed above, then I am confident that it is merely the ABS self-test. Your Owner’s Manual will have a brief description of this normal situation.
Thanks for the info. However, I’m very suspicious that such a significant amount of rust can build up over night.
Actually rust can and does often form overnight, especially in areas with high humidity.
Brakes are often affected because cast iron rusts very easily.
Walk into a parts store, buy a pair of brand new brake rotors or drums, clean any rust preventative substance off (it’s there for a reason), and allow those parts to sit outside on a humid night. Odds are they will be rusted in the morning without their ever having been installed on a car.
About That Grinding . . .
. . . How long does it grind . . . just once, several times each episode, all the time, how long until it goes away ?
Does it just seem to do this once while backing out of your short driveway ?
I agree that it could be rust, but depending on the conditions and answers to the above, VDCdriver could have the answer. Do these cars have ABS (Anti-lock Braking System) ?
I’ve got ABS on several cars (unfortunately) and what he is eluding to is normal operating behavior on just one of my vehicles (different make from the others). It’s checking the system and would be disconcerting to somebody not aware that this is what is taking place.
Check the owner’s manual for a discussion of this under ABS brakes. It could be in there.