for about 4 or 5 hundred dollars and a days work you can change all four calipers loaded with new pads and a new master cylinder ,a sure way of no crud in the system! and a like new brakes system. I did this on my 81 Sd as soon as I got it as when I tried to put new pads in the front I found a frozen piston and figured that for the price of a set of tires I could replace all the importion parts and could rest easy with my brakes for some time.I pumped new fulid through the lines to clean them out before I installed the new calipers.
William Rogers.......