Excessive brake travel on 94 Grand Am

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Hi!

I have a 94 Grand Am V6 with ABS brakes and drums on the rear. When the car
is running, the brake pedal travels almost all the way down to the floor. It
can stop the car just a little bit better than a car with a full 2 circuit
master cylinder, whose brake line/hose is ruptured. When the car is NOT
running, the brake pedal feels normal (firm with little travel). The pedal
is very spongy at all times when the engine is running. No amount of pumping
will firm it up.

The rear brakes are freshly lined, cleaned, and adjusted.
Both pistons in the wheel cylinders move freely, as do the adjusting star
wheels.
There are no leaks in the hydraulic system.
The caliper pistons move freely.
The disks and pads have yet to be changed but are functioning properly.

The entire system was bled like a conventional non-ABS system with the
following exception: since there are no fittings at the actual master
cylinder, I used the two bleeder screws on the ABS module. I not only bled
for air, but I pumped enough fluid through the system to change most of the
brake fluid.

When the car is first started, both the "brake" and "ABS" lights turn on for
a couple of seconds to indicate that the bulbs are not burnt out. After
that, they remain OFF.

Any ideas?

Thanks, Jason



Re: Excessive brake travel on 94 Grand Am

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Sounds to me like you've got air somewhere in the system.
ABS-capable scan tool may also be needed to bleed certain ABS systems
if air has gotten inside the ABS modular assembly....
Two links that might be of use:
http://www.brakeandfrontend.com/tsbrake/9014.htm
http://www.abrn.com/abrn/article/articleDetail.jsp?id=58824

It's been ages since I've had to pressure bleed a system so I'll leave
the personal tips to the more experienced guys here in the group. But
I'll bet that you've had air drawn into your system somewhere.

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