[mustangman65_79]

First u need to find out of the disk came stock.

If they didn't, then u need to buy a new master cylinder, and proportioning valve.

If they were stock, then my guess u either have air in the front, or u need a new master cylinder. Proportioning valves really never go out, all they do is limit the amount of fluid to certain parts. But make sure u do have one installed.