I have a 2011 HHR LT 2.4, auto trans. It has 115,000 miles and in great condition. When I first accelerated wide open through the gears and started to apply the brakes, the pedal was soft, moved to the floor but still had slow stopping. It felt like the pedal when you put front brake pads on and forget to pump the brake up before you move. The pedal seems like it has little to no vacuum. This continues for about 5 minutes or so. Under full acceleration the vacuum would be minimum. the vehicle drives without any problems when driven normally.

Has anyone experienced this condition?
Thanks, Dan

 

sounds like a brake booster or check valve?? Maybe a damaged hose or wrong connection?

 

The self adjusting part of the rear brakes typically does not work well at all. So the front brakes have to do all the work.

 

Not a direct comparison but on my Land Rover, it did this and I replaced the Master Cylinder and disconnected the ABS brakes. It was a 1997 model and the ABS brakes were more of a theory on them. It displayed much longer stopping distances but the brakes were much firmer.

Have not seen this on my 2006 LT with 230K miles on it. maybe loose suspension components causing calipers to open up more which would need more pedal travel to close ??

 

The brake flex hoses can swell and go spongy when hard braking.
There could be a vacuum leak in the booster vacuum hose.
the rear brakes need to be properly adjusted, there should be just 3 clicks on the EBrake lever to engage the E brake.
there could be air bubbles or water in the brake fluid.
the ABS system is finicky, have the system flushed and replace the brake fluid DOT 3 and bleed correctly