A complete drain and refill of the cooling system at least every 30,000 miles (48,000 km) or 3 years will remove the accumulated rust, scale and other deposits. The recommended coolant for most late model vehicles is a 50/50 mixture of ethylene glycol and water for year-round use. Choose a good quality antifreeze with water pump lubricants, rust inhibitors and other corrosion inhibitors along with acid neutralizers.
Before opening the radiator petcock, spray it with some penetrating lubricant.
- Drain the existing antifreeze and coolant. Open the radiator and engine drains (petcocks) or disconnect the bottom radiator hose at the radiator outlet. The engine block drain plugs can also be temporarily removed to drain coolant, but they are often hard to get at and it is not really necessary for this procedure.
- Close the petcock or reconnect the hose (and install any block drain plugs which may have been removed), then fill the system with water.
- Add a can of quality radiator flush.
- Idle the engine until the upper radiator hose gets hot.
- Drain the system again.
- Repeat this process until the drained water is clear and free of scale.
- Close all petcocks and connect any loose hoses.
- If equipped with a coolant recovery system, flush the reservoir with water and leave empty.
Determine the capacity of the coolant system, then properly refill the cooling system with a 50/50 mixture of fresh coolant and water, as follows:
- Fill the radiator with coolant until it reaches the radiator filler neck seat.
- Start the engine and allow it to idle 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 engine coolant overflow tank with coolant to the FULL HOT mark, 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.