Toyota Repair: Rear brakes, wheel cylinders, wheel cylinder

Question
I have a 1992 Toyota Previa with 216000 miles. I replaced the rear brake shoes and the wheel cylinder leaked i then replaced the wheel cylinder on both sides. every time i test drive the car the wheel cylinders leak. I noticed that the load prpostioning valve bolt was broke could this be the problem?  

Answer
Let me understand this, after you replaced the wheel cylinders they still leak, is this correct?
Is the leak at the backing plate or inside the drum?
Make sure that the bleeder valves are tight and the brake lines where they connect to the cylinders.
The proportioning valve will not cause the leak.