To determine whether the coolant needs replacement, a comprehensive assessment can be made from multiple aspects such as colour, odor, sediments, and instrument testing. Normal coolant should remain clear and transparent, with colors like pink, green, blue, or yellow, and show no signs of turbidity or darkening. Odor inspection can assist in judgment: deteriorated coolant emits a sour and foul smell, while normal coolant has a faint sweet scent. Additionally, if foam or impurities are detected in the expansion tank, or if the freezing point measured by a refractometer exceeds the local minimum temperature, it indicates degraded coolant performance necessitating replacement. Coolant regulates engine temperature through major and minor circulation cycles. Prolonged failure to replace it will elevate the freezing point and lower the boiling point, potentially causing coolant passage blockage. Replacement is recommended every two years or as specified in the vehicle manual, with preference given to OEM or reputable brand products. Immediate system inspection is required when the coolant warning light illuminates on the dashboard.
