Chattering when car is off, dead cold

[northwest]

Snowed in in the misty woods today, so decided to take my FIRST look under the hood of my '08 with ~400 miles on it.

After checking to see that the right amount of oil had indeed been filled, I replaced the dipstick and as I straightening up, a quick chattering noise -- almost like a rattlesnake sounded just ahead of me....If I had to guess I would guess it may have been coming from that black box that says "relay" on it.

Noise lasted about 1/8 to 1/2 second or so

The car is dead cold. Hasn't been driven for some 24 hours and the ambient air is about 23 degrees....so I KNOW it wasn't a rattlesnake -- in this weather it would have been a snake-sicle. Gee, maybe it was just so cold that the car's teeth were chattering

Any thoughts? Is this common? no warning lights when I moved it some 40 yards yesterday morning...

[jayman]

The brakes in the Prius are electric assist. Sometimes the boost pump will briefly run when the car is off. Now that I think about it, yes the boost pump does sound like a rattlesnake

The noise lasted 3-5 secs?

[northwest]

Originally Posted by jayman

The brakes in the Prius are electric assist. Sometimes the boost pump will briefly run when the car is off. Now that I think about it, yes the boost pump does sound like a rattlesnake

The noise lasted 3-5 secs?

I really can't say how long it lasted....as mentioned....I guesstimated about a 1/2-second....but I was so startled that it took me a second or so...so outside length maybe 2 seconds....maybe as little as 1/8 second, but probably longer...

Interesting about the brakes. I know about Hydralic assist, but electric..

[jayman]

My 2007 FJ Cruiser also has electric assist brakes. However, unlike the Prius, they are QUIET.

If I'm stuck at a red light for a long time, I can sometimes feel the buzzing vibration in my foot, letting me know the brake boost pump in the FJ is working

Every time I've heard my Prius boost pump rattle, it sounds like for 3-4 secs. I too was very surprised the first time I heard it

[qbee42]

The Prius also does a pump down test on the fuel system to check for leaks. It only does this after the car has been parked for an extended period.

Tom

[northwest]

Originally Posted by qbee42

The Prius also does a pump down test on the fuel system to check for leaks. It only does this after the car has been parked for an extended period.

Tom

Man, what a car....a far cry back from the days when I used the belt from my Levis to replace a broken fan belt on my '62 Ford Custom to enable me to limp into town.

I suppose that next you folks will tell me that the Prius measures my blood oxygen level as I clutch the steering wheel and feeds or restricts fresh air intake into the cabin, based on the results..

[seasalsa]

Originally Posted by northwest

I suppose that next you folks will tell me that the Prius measures my blood oxygen level as I clutch the steering wheel and feeds or restricts fresh air intake into the cabin, based on the results..

Maybe not, but it does measure the humidity of your breath and adjust the climate control accordingly.