2. Take a look at the hoses and connections to and from the radiator. Squeeze the hoses to check for deterioration. If any hoses are swollen near the hose clamps or have soft spots or cracks, replace them. Replace hose clamps if they bind or will not tighten. Replace the thermostat since it's cheap and your draining the coolant already 3. If you feel a crunching sensation when you squeeze the hoses you probably have rust in the cooling system. The system will need to be flushed before filling with new coolant. There are kits to do this at your local auto part store, but if you would rather do it yourself follow this procedure: