Do extremely rusty disc brake rotors/pads need to be replaced?

Question

Toyota Prius that has been outdoors and not driven for 2 years has extremely rusty disc brake rotors. Sorry, I don't have any current photos or access to the vehicle.

The rotors and pads were satisfactory (normal levels of rust on the rotors) before this 2 year period.

The rotors and pads do not need to be replaced due to wear, but the mechanic (who seems to hopefully be the rare trustworthy mechanic) is recommending replacing all the pads and machining the rotors due to the severe rust.

The mechanic has said he is willing to try to drive the vehicle a little to see if that takes care of the rust. But if not, he provided a large quote to replace the pads and machine the rotors.

Besides driving the vehicle to try to wear the rust off, or machining the rotors and replacing the pads, are there other possible solutions/tips?

Also, obviously rotors rust, but do modern brake pads rust too? If not, is there any reason to replace them (they are not worn)?

Answer 1

Repair shop liability issues dictates SAFETY FIRST. Brake repairs are safety issues so there's no cheap economical repair. However, you can, if possible, seek out another repair shop and ask for an estimate. As a rule, rotors and brake pads wear into each other and invariably create a slight taper from hub to outer perimeter and sometimes warp, described as runout on rotors. If rotors are serviceable with machining, new pads are recommended because the original pads have a slight taper that can't be seen by the naked eye. If you can't see 0.002" of runout on worn rotors, you may not feel it as a pulsating brake pedal. Worn (tapered) brake pads may or may not be seen on brake pads and reusing them on machined rotors will not seat properly, creating loss of braking effectiveness. In effect, machined rotors with old brake pads is a recipe for unsafe braking. You also have the choice to replace rusted rotors with new ones, along with new brake pads. And, unavoidably, flushing and bleeding the brake system is recommended every time brakes are replaced. Your safety is important. There's no price for safety if you consider less than correct brake repairs.

Answer 2

Rust on rotors obviously is normal, and normal braking will clean this surface rust off in a short time. But after two years of sitting, it's very possible or probable that the rust has penetrated too far into the rotors surface to get away with that. The rotors probably need turned. Pads should be fine, but they may be worn to the point that they may not need replaced yet, but they may need to be replaced in the near future, so the mechanic may be trying to save another service call in the near future. If this is a trustworthy mechanic, as you say, it's probably best to follow his advice. If you're skeptical get a second opinion. You may find one that you trust more.

Answer 3

Even two years of rust will not have degraded the rotors in any significant way. You might get a bit of pitting but that will actually help braking performance - just like more expensive dimpled discs.

Similarly, the metal backing of the pads will not have degraded in any meaningful way. It is unlikely that the friction material of the pads will have degraded, because pads can easily last more than two years in light usage, so the material is unlikely to degrade in that time.

In summary, drive the car and do a lot of hard braking. That will clean surface rust from the rotors and will bed in the pads. I will be very surprised you have any issues at all. If the braking feels fine after this bedding-in then they are good.

Answer 4

It depends whether there will be vibrations when you remove the rust or not. If so, you should remove at least the rotors. The best way would be to machine the rust off - in that case you may get an even surface, if not possible, drive it then.