hydraulic sound

I noticed the same sound and I have no idea what it is. Does anyone know?

 

I'm fairly certain it isn't lifting the front end. This is not a hydraulic suspension. It does sound sort of like a compressor, and I notice it when I go to my car in the morning as I reach for the door handle. I imagine the proximity sensor (which illuminates the interior when you get close) may assume you are about to enter and start the car, and this is some kind of prep for starting/running? That is my best guess. What it actually is, not sure. Quite sure it isn't a problem.

 

That sound is the brake accumulator pump pressurizing your brake system. You'll notice that it only makes that sound if the car has been parked for awhile.

 

Ah, the brake accumulator pump. I've had my Prius for exactly three weeks now. When I open the door and hear that noise, I had concluded that the car was "winding itself up." There are also some "knocking" noises that occur sometimes when the car has been sitting still, engine off. "Winding down," maybe?

So here's a question about the brakes: Sometimes when I first start up and brake, such as while backing out of the garage, the car stops severely, and I can't seem to brake very gently. This is occurring at a very low speed--say 2 mph.

 

That is the friction brakes (the normal brakes on most cars) being a little grabby from lack of use. The regenerative braking does most of the work so like any brake that hasn't been used much it will grab a little.

As far as the noise when entering the car it I just assumed it was the coolant system pumping hot liquid out of the thermos like on the GII but I think I read somewhere that the GIII doesn't have that? Can anyone confirm? I did notice it only happens on the driver side.

G

 

The Gen III does not have the coolant pump or thermos.

Tom

 

The grabbiness is not from lack of use. This is a myth. The reason that they are very grabby at low speeds, is that unlike a traditional car, which has the motor 'push' you along to inch forward, which requires the brakes to use more effort to stop against the pull, in the Prius, the moment you apply the brakes when inching forward, the forward (or backward if in reverse) motion of the electric motors stop inching you along, and you just stop the car.

At first I thought that this was just a problem with my car, but after speaking with other Prius owners, they also confirmed that is seems as though the fact that we are braking without fighting the momentum of the engine trying to push us along is why we all seem to have this 'issue' with the Prius. Now that I have gotten used to it, I see it more as a feature than an issue.

 

In the last month of driving daily, I've only experienced grab once. Either I've gotten so extremely used to it that I totally compensate, or perhaps it was related to brake grab from under-use. It certainly felt like brake grab that I've experienced before.

I guess the proof would be to see if it ever crops up again for me, and if so, does a firm braking in N make it go away or not.

 

Lack of use does contribute to grabbiness. Prius brakes are often rusty. That exception aside, the rest of your post is correct. The lack of a big engine and automatic transmission forcing the car forward is a major contributor to the feeling of grabbiness. The Prius does simulate some creep, but obviously that runs against good fuel economy, so creep is kept to a low level.

Tom

 

I had this brake problem only backing up.
and.. it only happens some of the time.. not all

It continues.. I am trying to figure out what makes it grab.

Scott