You probably have air in the lines. To bleed the lines, there is a bleeder behind the rear end. You need to hook up a clear vinyl line to the bleeder and run it into a clear jar. Then, there is a lever which needs to be disconnected and brought down to the six o'clock position. Make sure the resevoir is full, crack open the bleeder, and let the fluids run into the jar and check for air. Make sure you don't run the resevoir empty and it helps to have someone keeps the eye on it so you don't run it down; it doesn't take long. You need to start the car for the fluids to pass through the lines. When you are getting clean fluid and no air, close the bleeder, shut off the car, and fill the resevoir to the proper fill mark. Hope this helps. If your system still doesn't work, you might have problems with the air cells. You can tell by pushing on the bumper, if you have a really soft or bouncy rear end, the air cells are shot.
-Shadetree