Changing Antifreeze
| 30 November 2001
When changing antifreeze, the usual mix ratio is 50% antifreeze and 50% water. The mix can be anything you decide but less than 20% antifreeze may not provide enough lubrication for the water pump or enough anti-corrosion for the cooling system. Using distilled water (available at grocery stores and other places) for the mix will help reduce corrosion and sediment in the system. After draining and flushing the system, it's time to close the drain and put in the new antifreeze.
An easy way to achieve the 50/50 (or other) mix ratio is to install the antifreeze first. If you premix first (to 50/50 or other ratio) your system may not have enough room for the whole amount. That's because residual water from the flushing process is using some of the room. So after looking up the capacity of the system, pour in the amount of antifreeze you need for the ratio you selected. For example, if you are using the 50/50 ratio, pour in the amount that equals half the capacity of the system. Add distilled water to complete the fill process, install the radiator cap, and run the engine up to temperature to thoroughly mix the new solution. Let the engine cool back to room temperature and check to make sure the cooling system is filled to the correct level; top off as necessary with a premix of your ratio. Any antifreeze additions for maintenance reasons (between changes) should be made from a 50/50 (or whatever ratio you are using) premix. Note that some of the newer Mustangs require special filling techniques to assure that all of the air is out of the cooling system.