Chevrolet Sonic Repair Manual: Coolant System Flushing
- Do not use a chemical flush.
- Store used coolant in the proper manner, such as in a used engine coolant holding tank.
- Do not pour used coolant down a drain. Ethylene glycol antifreeze is a very toxic chemical.
- Do not dispose of coolant into the sewer system or ground water. This is illegal and ecologically unsound.
- Various methods and equipment can be used to flush the cooling system. If special equipment is used, such as a back flusher, follow the manufactures instruction. However, always remove the thermostat before back flushing the system.