How To Flush and Fill the Cooling System Haynes Shows You How

Take a look at your car's owner's manual, or the recommended service schedule in every Haynes manual for suggested coolant change intervals. Some models need a change every few of years but some modern cooling systems are considered "lifetime fill" from the factory. Remember, when a manufacturer says something will last a lifetime, they mean it will last longer than the warranty, typically 5 years or 100k miles.

If you don't know the last time the coolant was changed, and the car is more than 4 years old, change it now. Part of the cooling system service involves flushing (draining, filling with water and draining again), but if you change it regularly flushing isn't needed.

You should always check the radiator and heater hoses when draining the system to change the cooland and replace any that are old, cracked, or swollen.

All cars are slightly different, so if it is time to change your coolant, use our before you begin checklist, and find your car for specific instructions.

The antifreeze/coolant in the motor keeps things from getting too hot, and unlike water, won't freeze if you leave the car parked outside in winter. Coolant is more resistant to boiling as well as freezing, and prevents internal corrosion, and is most effective when mixed with plain water 50/50 for maximum protection against boiling and freezing, and optimal cooling. Over time the antifreeze chemicals in the coolant lose their effectiveness, especially if you top up the coolant with water regularly. In harsh winter weather this can lead to damage from the coolant freezing and expanding.

Periodically, the cooling system should be drained, flushed and refilled to replenish the antifreeze mixture and prevent formation of rust and corrosion, which can impair the performance of the cooling system and cause engine damage. The lubricating chemicals in the coolant for the water pump and thermostat also need to be replenished occassionally.