77Nissan280Z

When im driving an go to hit the brakes there is like pause briefly then it goes through to slow me down..but it veeres to the left...i just replaced the brakes too...and then also when i shut the car off i hear what sounds like air pressure being released by the brake fluid filler area...whats that?

FASTLANECRX@AOL.COM
please exscuse the lame address...