Drain coolant system and run clean water through entire system. This will remove most contaminates. If you've used a water glass/silicate based sealer prior to using Dura-Seal®, you will need to purchase our "Water-glass Flush Agent" before using our sealer.
It's not required to remove the thermostat as our sealer cannot cure or clog that area, but, if left-in, it will slow the process by restricting flow. Next, pour the Dura-Seal, and Extreme Powder Pack into the radiator, (no radiator cap?) disconnect upper radiator hose from engine and pour sealers into hose (they will flow to radiator). Fill system with water.