I got in the Bu today and when I went to apply the brakes they went to the floor. It felt weird, so I eased around the block. The brakes would bottom out and on ocassion the front brakes would lock down. Me and my cousin decided to try and bleed the brakes but we got no fluid out of the rear brakes on the drivers side. The rear passenger side let out a little air. We looked a little closer under the car and noticed that the proportioning valve might be leaking. Just looking for any help or comments on what to do next. I have somewhat looked for a proportioning valve but have had no luck other than the one at gbodyparts.com. Any help is appreciated.