Noise under engine after power down

It might be your catalytic converter. You should jack up the car and get under, remove under covers so you can get a better look and find out exactly where it's coming from.

 

"turn up your radio...!"
Hard to tell from here. it sounds like a shield rubbing, or a waterpump, idler bearing. Or check the belts if loose or needs replacement or belt dressing. check your catalytic or manifold shield. check you exhaust flange. I couldn't make it up in your video. Not loud enough or atlease rev it when your running your video so you can see the action of the engine of its moving or tilting while reving. A busted mount will actually contribute to that sound if the motor is not sitting properly...

 

No belts on a gen 3 prius

 

So it only does it when the car has bee running and hot, right? I'm suspecting catalytic converter and/or some heat shields just cooling down and wouldn't worry about it.
I've gone out into my garage and heard noises coming from the Prius that hadn't even been ran that day and discovered the evap system sometimes does air cycling even when the car isn't being used.

 

Solrunner wrote:
"It occurs after driving, parking, and turning off the car."
Doesn't he?

Mat

 

Does the sound start immediately after shut down, or there’s some delay?

just grasping at straws.

 

I heard in once again and have a feeling, sort of "I heard it already!".

No idea when and where and what was it - sorry...

The sound is to "dynamic" for me to be some part contracting on cooling making it.

I suspect some pressurized gas decompressing - evaporating system, cooling system, braking system (what I can think of).
Non of the above is actually good leaking pressure

Interesting is, it can be heard actually all over the motor compartment...

And - are you sure, the sound comes up only if the engine is off, or if it is running too, but is not loud enough to be heard?

Could it be one of the pistons? If it has stopped short from being ignited? Is it technically possible?

Mat

 

I'm gonna go with A/C. If you have driven, parked, and turned off the car while the A/C was running, then right when you turn it off, the refrigerant is mostly stuck on one side of the system as liquid at around 220 psi, while on the other side it is vapor at around 30 psi. The liquid on the high side will be squirting through the TXV for a while and boiling off into vapor on the low side, until eventually both sides are matching at around 90ish psi (more specifically, both sides will end up at the "saturation pressure" for R-134a at whatever the surrounding temperature is).

That is one kind of "leaking pressure" that isn't any kind of problem at all.

Edit: an easy way to check if I'm right would be to go make a similar drive but without using the A/C at all.

 

Just heard identical sounds today on our 2011 Prius after running the car for only a few minutes with the AC on to check all the signal lights and exterior lights prior to getting an annual safety check.

It's the AC lines or compressor, it's normal, I wouldn't worry about it.

Posted via the PriusChat mobile app.

 

Precisely. It's liquid R-134a squirting through a tiny expansion valve and boiling off into R-134a vapor. Once you turn the car off and the compressor stops, it'll just do that, until it reaches the same pressure on both sides.

 

Refrigerators do that too, for the same reason.

 

Only by accident! There's a Master Toyota Technician on YouTube, Ahmed ("The Car Care Nut") who said he's lost count of new hybrid owners who return to the dealership complaining their hybrid is broken, makes all kind of weird noises from the "UFO" speaker when you drive slow or backup, to the regenerative brakes charging the brake fluid when you open the door to the evap system.
He, also, warns folks over and over to NEVER top off their gas tanks when filling up because he's seen folks who do this getting gas in their evap cannister and it has to be replaced.