Hummer H2 - brake pedal goes to floor

With the engine running, vehicle not moving and medium pressure the brake
pedal will go all the way to the floor. When driving brake performance is
good, stops well and ABS will come on.

Dealer says pedal going all the way down is normal, related to hydro-boost
system.

I am concerned - how can pedal go all the way down if there is not
something wrong with the master cylinder?

"Reno" > schrieb im Newsbeitrag
...
> I am concerned - how can pedal go all the way down if there is not
> something wrong with the master cylinder?

Have your checked break fluid level?
I haven't driven the Hummer yet, but this is signification for air in the
system.

Regards,

Ralf

On Jun 11, 12:46 pm, Reno > wrote:
> With the engine running, vehicle not moving and medium pressure the brake
> pedal will go all the way to the floor. When driving brake performance is
> good, stops well and ABS will come on.
>
> Dealer says pedal going all the way down is normal, related to hydro-boost
> system.
>
> I am concerned - how can pedal go all the way down if there is not
> something wrong with the master cylinder?

So let me get this straight..brake pedal goes to the floor with the
vehicle running, so what do you do, you DRIVE THE THING? What state
are you in? What city? I don't want to be driving anywhere near your
street-legal road tank.

And thanks for confirming only idiots buy hummers..how's your gas
mileage BTW?

Chris

Reno wrote:
>
> With the engine running, vehicle not moving and medium pressure the brake
> pedal will go all the way to the floor. When driving brake performance is
> good, stops well and ABS will come on.
>
> Dealer says pedal going all the way down is normal, related to hydro-boost
> system.
>
> I am concerned - how can pedal go all the way down if there is not
> something wrong with the master cylinder?

No hummer here, but I have a 3500 dually pickup with hydroboost and it
definitely doesn't behave as you describe. Pedal behavior at idle is
pretty much the same as at speed, and it will not go all the way to the
floor unless there is air in the system.

I'd test drive a hummer at a different dealer or two to confirm that
it's not a design "feature" on that vehicle, and if the others behave
properly then I'd pressure the original dealer to fix it and / or
contact GM direct.

Reno wrote:
> With the engine running, vehicle not moving and medium pressure the brake
> pedal will go all the way to the floor. When driving brake performance is
> good, stops well and ABS will come on.
>
> Dealer says pedal going all the way down is normal, related to hydro-boost
> system.
>
> I am concerned - how can pedal go all the way down if there is not
> something wrong with the master cylinder?


The only difference with hydroboost is the source of the assist
pressure. In a vacuum system it is vacuum on the diaphragm and
atmospheric pressure on the other that give you the assist. In a
hydroboost it uses the hydraulic pressure from the power steering
system. The rest of the brakes are the same.

How about this. With the engine OFF what does the pedal do when you step
on it?
You say that the ABS comes on. What are the road conditions when it
comes on?

--
Steve W.

"Steve B." wrote:
>
> On Wed, 11 Jun 2008 21:41:40 -0500, "Pete C." >
> wrote:
>
> >
> >Reno wrote:
> >>
> >> With the engine running, vehicle not moving and medium pressure the brake
> >> pedal will go all the way to the floor. When driving brake performance is
> >> good, stops well and ABS will come on.
> >>
> >> Dealer says pedal going all the way down is normal, related to hydro-boost
> >> system.
> >>
> >> I am concerned - how can pedal go all the way down if there is not
> >> something wrong with the master cylinder?
> >
> >No hummer here, but I have a 3500 dually pickup with hydroboost and it
> >definitely doesn't behave as you describe. Pedal behavior at idle is
> >pretty much the same as at speed, and it will not go all the way to the
> >floor unless there is air in the system.
>
> Try it tomorrow and see how far you can push the brake pedal. We had
> a fleet of astrovans and you could push them all to the floor with the
> engine idling if you wanted to. The vans all stopped normally with
> normal pedal travel but you could push the pedal on down to the floor
> if you tried to. These were all new vans. I think this is what the
> OP is doing, but I could be wrong.
>
> Steve B.

Nope, no difference in pedal behavior between idle and moving. The pedal
does not travel more than about half way under any sane amount of
applied pressure.