Crunchy Sound When Coming to a Full Stop

is this your first prius?

 

I hear a clunking noise once in a while when coming to a stop. I have seen other threads here discussing similar items. My theory is one of two items or both. To reduce drag on the calipers, they are made to completely release from the disk and not rest against the disk. The clunky sound is when they actually engage against the disk. Or it could be something to do with the DC charging apparatus on the wheels engaging or disengaging.

 

I had a clunking sound and ended up having to take my Prius in and having bolts put in my rear suspension because they had loosened to the point of almost falling off! Glad it wasn't something dangerous, rear suspension malfunction I can handle with a few cuss words but front suspension nope.

 

there is no charging apparatus on the wheels, it is all in the tranny. could be the brake pads, they move back and forth a bit with forward and reverse.

 

good to know. I never knew where it charged from. I think the salesman said "everything that turns charges the battery". LOL never trust 'em!

 

yip.

 

I think its the brake regen system

 

My 2013 Sonic had springs that would push the pads a away from the rotor after releasing the pedal. Such systems are likely common on all cars now.

 

Most likely it's totally normal - it may be your brake pads against a rough disc surface. The friction brakes often don't get used at all for a long time on a Prius (because the "regenerative brakes" are your electric motors turning in reverse to slow the car and charge your batteries), but they are needed to get from a very slow speed (8 MPH in the Gen 3, even slower in the Prime) to a complete stop. It's SoCal so you don't get much rain... but is the sound worse after it rains?

 

maybe test drive another at the dealer.

 

You could be hearing the mechanical brakes finally kicking in - they don't kick in until you get below 5 mph. You could also be hearing the noise maker. When you're in electric mode below a certain speed, there's a noise maker that some say sounds like growl or rocks rolling around in a can. I can't hear it. Maybe yours is louder than others?

 

If you washed the car and left it overnight the brake disks rust a bit. If you then drive it "gently" the friction brakes are only applied for the last second or two of stopping. It sounds "crunchy" or like sandpaper rubbing. Only lasts a few miles. I found it amazing how much stopping power regen has (when the car was not making the "crunchy" sound).
You can confirm it is the rust by stopping hard a few times, then seeing if the sound is gone.

 

Rust on the rotor is a likely culprit, but it should disappear after a hard stop or two that go right to friction braking. The rust is usually visible on the rotor through the wheel spokes.