Sound when stepping on brake first time in the morning

This subject has been discussed several times in this forum. It appears to be a problem for every Prius V owner, including me. It appears Toyota doesn't know what is causing it and currently has no intentions of a recall.

 

Here's one that talks about brake caliper noises:
Brake Calipers Noise?? | PriusChat

Also this one:

Brake noises - normal or not? | PriusChat

 

Check out the following thread: 2012 Prius v Groaning Noise | PriusChat

Over 6 pages of comments.

 

Check out the links I posted. Here is one more:

Squeals like a pig | PriusChat

 

I hear this sound at times. It almost sounds like something is running around inside the engine bay. I'm guessing it has something to do with the same mechanism, I think brake booster, that pulls brake fluid down when you open the driver door.

 

The calipers "float" over the brake disc... when you apply the brake - a piston pushes the pad against the disc ... the floating - allows the inside and outside pad to wear evenly - (generally piston side always wears more) ... but also allows for any 'wabble' for lack of better term in the brake surface ... it's not uncommon - especially on cars with rear disc brakes ... that the calipers "stick" on the pins and don't freely float as they should...

usually the fix - is to pull the bolt/pins lube them up with a special grease that has silicate in it - then put them back together... road grime, water, etc. gets its way in there and the caliper will 'rust' fast to the pins...

the clunk - could be that caliper - popping loose as you squeeze the rotor with the pads ... after the first time for the day - its knocked loose and floats as it should --

this is speculation obviously - as there are many noises and many causes of noises...

but i have experienced something similar with my suv - and that's what it was.

 

This sound is coming from the engine compartment, and sounds like something is bouncing around in there a few times, and then stops. Brake pedal is firmly pressed so I don't think it has anything to do with that area.

 

Not sure where in CA you live, but King Tides in Newport Beach?

 

Can you correlate w/ rain? Might be a slight bit of rust between the pads and rotors and the clunk is simply breaking the bond the first time the vehicle moves. This can also occur after washing the car and not driving right away.

Just a thought, it could be something different, but I've answered many times as tech support for a brake company, often after the customer washed the car.

 

take note as well if the ICE is running ... and then shuts off....
you could be getting a little engine rattle as the ICE shuts off when you step on the brake to stop....

can you post a link to a video of the issue?

 

This is what I was thinking too. Rotors will get a coat of rust overnight if wet or very humid.

 

My wife has reported the same problem twice in the last month -- her description nearly identical to jzchen's in #9 above. Nature and location of noise confirmed by her sister, who was standing outside the car waiting to get in after wife backed out of the garage. Florida summer, no correlation with weather events, garage is dry, only has happened (so far) on first trip of the day. I'll keep looking...