Video tutorial on how to test the freezing and boiling temperature of your vehicle's coolant. WHEN REMOVING THE COOLANT SYSTEM'S CAP, ENSURE THAT IT IS COOL ENOUGH SO THE LIQUID WOULDN'T BE UNDER PRESSURE. This is a very important because it determine's the antifreeze (glycol) and water ratio. This allows you to drive in extremely cold climates to prevent your coolant from freezing and also maintains your vehicle's coolant temperature in warmer climates to prevent it from boiling. When adding more antifreeze (glycol), ensure that it is the correct type which meets your vehicle's specifications. As for water, add only distilled water because it does not have any additives which can plug up your coolant system. The antifreeze tester is an inexpensive tool which can be found at any local auto parts store. Some procedures will vary depending on the style of antifreeze tester, please refer to the guidelines on the tester. A premixed coolant will not allow you to adjust the freezing or boiling values. This particular tutorial was done on a 1997 BMW 540i.