When opening the driver's side door of my 2008 pkg. 6 Prius, there is a rat-tat-tat sound from under the hood. It will continue every 30 seconds or so for a few minutes. This happens whether or not I have the keyless fob near the car. It also happens when entering or leaving the car. Opening the door triggers it whether the car is hot or cold. Toyota mechanic said it was the coolent transfer, but why would it happen when you open the door? It sounds more like a small machine gun than a movement of fluid. Any thoughts would be appreciated. rhymer
Are you sure someone didn't replace your engine with a 2-stroke dirt bike engine? Anyway, I'd listen to another Prius and compare. I'd imagine it's the coolant transfer getting ready for you to start the car or something.... The Prius makes all sorts of occasional automatic noises. Perhaps whatever your noise is is a component that's supposed to automatically happen...but perhaps that particular component is about to fail and therefore louder than usual? Your best bet is probably to see if you can hear another Prius make that sound or else I live on williamsfield/Gilbert so I'm probably not too far if you want to listen for it on mine. Mike
On my '06 I noticed the sound got a bit rough after about 6 months. The '08 makes a noise as well, but it's much smoother. (However the car is brand-spankin-new)
The rat-a-tat-tat sound is probably the brake accumulator pump. The Prius uses an electric pump to pressurize the power brakes. It runs at random times, but usually about every third time you press the brake pedal. I'd be really surprised if your door had anything to do with it. The coolant transfer pump makes more of a whirling sound, and runs right after you shut down. Tom
that noise is a relay from the fuse box located on drivers side, i believe it starts up the braking system or something.
And the relay chattering because ....... ? The starter relay will do that when the battery's almost dead in a non-hybrid. But why would a relay be chattering if everything's working properly? I know the Prius is a different breed, but in my experience is that a chattering relay has never been a normal event, unless it was used as an alarm, power to the relay goes through it's own contacts, making it a buzzer or an alarm. There's a lot to be learned about these new fangled contraptions.
It's not a relay. There are a couple of relays that engage when you power on, but they don't chatter. The chattering is the brake accumulator pump, which I won't bother to describe again. Tom
I don't understand why the brake pump would be triggered by opening the drivers door. I assume this behavior is reliably reproduced by opening the drivers door after the car has sat idle for some time?
It's not from opening the door(s). That's just a co-inkydink. It'll happen before or after opening the door. Sit there long enough, & it'll go off before the door opens, sometimes. Jump out quick, & it'll go off after, sometimes. But sometimes, not at all. It just depends on the need for recharge.
Spent some time with my Toyota Service Manager, and he listened and convinced me, as did Tom, that it was the brake accumulation pump, and is a normal function on the Prius. Thanks for all the replys. Rhymer
