The system should be completely drained and refilled at least every two years in order to remove accumulated rust, scale and other deposits.
- Remove the radiator and overflow tank caps.
- Place a drain pan of sufficient capacity under the radiator and open the petcock (drain).
- Drain the coolant from the engine block either by removing the drain plug or disconnecting the lower radiator hose.
- When the system is completely drained, close the petcock and fill the system with a radiator flush. Clean water may also be used, but is not as efficient.
- Idle the engine until the upper radiator hose gets hot. Be sure to put the heater on to circulate the water or cleaning fluid through the entire system.
- Allow the engine to cool and drain the system again.
- Repeat this process until the drained water is clear and free of scale.
- Flush the overflow tank with water and leave it empty.
Determine the capacity of the coolant system, then properly refill the cooling system with a 50/50 mixture of fresh coolant (antifreeze and water), as follows:
- Fill the radiator with coolant mixture until it reaches the radiator filler neck seat.
- Start the engine and allow it to idle (heater on) until the thermostat opens (the upper radiator hose will become hot).
- Turn the engine OFF and refill the radiator until the coolant level is at the filler neck seat.
- Fill the overflow tank with the coolant mixture until the level is midway between the upper and lower level marks, then install the radiator cap.
- If available, install a pressure tester and check for leaks. If a pressure tester is not available, run the engine until normal operating temperature is reached (allowing the system to naturally pressurize), then check for leaks.
- Check the level of protection with an antifreeze/coolant hydrometer.
- After the system has cycled between operating temperature and cold a couple of times, check the overflow tank level and top up if needed.