Sinking brake pedal

[notaguru]

When I put my foot on the brake pedal and then push the ON button, the brake pedal gets "soft" and sinks nearly to the floorboard.

The dealer says this is normal behavior.

The car drives fine - no alerts, normal stopping, no strange noises.

In any conventional car I would assume air in the lines and simply bleed. This car has electronic brakes...

Is that sinking brake pedal "normal"???

[ssj4vegita2002]

Mine does the same. It is normal. I'm pretty sure this is the car's systems becoming "active" and allowing you to shift.

[zaxdude]

When I put my foot on the brake pedal and then push the ON button, the brake pedal gets "soft" and sinks nearly to the floorboard.

The dealer says this is normal behavior.

The car drives fine - no alerts, normal stopping, no strange noises.

In any conventional car I would assume air in the lines and simply bleed. This car has electronic brakes...

Is that sinking brake pedal "normal"???

Mine does not do this. I press on the brake, then the ON button, and my break pedal barely moves (if even at all).

[DCFusor]

I'm guessing you are feeling the transition between unpowered and powered power brakes here. When you first put your foot on the pedal, you've got power brakes with no hydraulic boost. As soon as that pump kicks in, the same pedal force means more pressure to the calipers, and a bit of expansion of the lines, allowing it to go deeper for the same pedal force.

If it keeps creeping down - you've got trouble. But try the same thing on a "normal" car with power brakes as the engine fires up and provides vacuum to the booster...I get that in my Honda truck which is otherwise a "normal" vehicle.

[saghost]

When I put my foot on the brake pedal and then push the ON button, the brake pedal gets "soft" and sinks nearly to the floorboard.

The dealer says this is normal behavior.

The car drives fine - no alerts, normal stopping, no strange noises.

In any conventional car I would assume air in the lines and simply bleed. This car has electronic brakes...

Is that sinking brake pedal "normal"???

It is normal for the pedal to get softer and to move down a little if you keep the same pressure on - you'll also here a pump running and feel some vibration through the pedal; it's just the car building the brake assist boost. It is not normal for it to go "nearly to the floorboard" unless you're stomping on it hard, and likely not then. Go to the dealer and ask to see what their demo Volt does, maybe? It should move some, but not that much...

[Slapshot28]

I played around with this, and was surprised at how much "travel" there was in my brake pedal on powering up with foot pressure applied. Normally, I don't press the brake very hard on power up, so I hadn't noticed this "softening" and increased travel.

It all sounds normal too me, unless the brake pedal really is going all the way to the floor with little or no effort.

[FrankIII]

How much pressure is being applied to the brake petal? When I start it up, I just put enough pressure on it to light the brake lights, then release it until after the car is fully on.

[dax777]

I've noticed some break pedal lowering on startup but hadn't given it much thought until this thread highlighted it...I will pay close attention next startup to see exactly how much travel is involved, but so far, it hasn't felt abnormal to me...

[QB 45]

I think DC Fusor hit the nail on the head - it's just the transition between unassisted and assisted brakes. Most ICE cars (my own included) will soften the brake pedal as the master cylinder builds its assistive hyraulic pressure.

[eplantz]

the brake pedal gets "soft" and sinks nearly to the floorboard.

when i picked up the car and sat in the car for the very first time, the brake pedal sunk to the floor. i was disturbed but the salesman said it was normal.


oddly, after 1+ year of driving, it never happened again.