Noise when stopping

Look under the driver's seat ...

 

addlepated

That sounds sort of like the noise I had suddenly in my Voyager. Scared me to death, and turned out to be a can of anti-static spray that was in the under-seat glove box. It had been moved from the one on the dash. Do you have something that might roll a bit?

Beth

 

<div class='quotetop'>QUOTE(addlepated\";p=\"94085)</div>

I've experienced this same noise on and off for the last 15,000 miles. At first I thought it was something in the car, but I have since ruled that out. As you stated, it sounds like a "thump, thump" that occurs just as the car comes to a full stop. To me, it sounds as if it is coming from just the other side of the firewall (more towards the center?) and does not occur every time I fully stop.

I have not noticed it in quite some time, but I have programmed my foot to let up ever so slightly on the brake as I come to a complete stop.

 

[font=Comic Sans MS:f196d74f4a]Could it be the thunk when the ICE stops hard? I've noticed that when the ICE is running and I come to a stop and all propulsion systems shut down, sometimes the ICE gives quite a shudder and it sounds like a thunk. I think it's the car trying to get the last milliwatt from the ICE.[/font:f196d74f4a]

 

No, it's definitely not the ICE. I have been able to reproduce it time and time again while running in full electric mode in traffic.

It is possible that the sound I hear is not coming from under the hood. This thump is so low in both volume and tone that determining it's source is difficult. If I am not mistaken, I believe I have also felt a very slight "bump" in the brake pedal that correlates with the sound. But then again, it is so subtle that I may be imagining it.

As I have never had any issues with braking or being able to stop over the last 15,000 miles, I am not too worried over this noise.

 

[font=Comic Sans MS:15eda635a5]A thunk noise usually means something is loose, and braking to a stop lets that loose thing hit a stationary thing.

It might be a shield in the exhaust system, perhaps checkable when the car is on a lift by shaking the pipe. While unlikely, it could be a motor mount failing, perhaps checkable by watching the engine when the ICE turns on and off. It might be a slightly loose brake component.

"Thunks" can be very hard to find, particularly if they are soft. On my Camry, my wheel lock socket came out of the holder I had rigged and was floating around in the spare tire well. I kept hearing an intermittent thunk/knock as it shifted around in the back. The only way I know it was the loose socket is that I found it when checking the spare's air pressure (you do that too, don't you?), put it back in its holder, and the clunking stopped.

Turn up the radio![/font:15eda635a5]

 

<div class='quotetop'>QUOTE(kjb516\";p=\"94724)</div>

Just to let you know, under normal operating conditions, the brake pedal hydraulics (master cylinder) is closed off from the wheel cylinders, so problems with the brakes (linings, rotors, etc) would not be felt with your foot like in conventional brake systems.

 

My wheel socket lock came loose in my Prius cargo section. It rattled around, and it was hard to tell exactly where the sound was coming from. It only takes a moment to check, so I'd suggest looking in the various storage areas. Have you checked in the compartment under the armrest?

 

This noise developed in my Prius at about 400 miles! I'm at 1500 now, and I think it's been getting steadily worse.

It seems to me to be related to the mechanical breaking system. It feels and sounds to me like my front left wheel is repeatedly catching as the car somes to a stop. This very clearly starts at 8 MPH (when regenerative braking kicks out and friction braking starts) and I can feel the entire car pulse with the noise. I was about to make an appointment at my dealer when I came across this thread.

The problem seems to occur the most when I try to make a "smooth" stop and keep the brake pedal in the same position under 8 MPH as above. As kjb516 noted above, it won't do it if I release the pedal slightly at this transition point.

Chris