Why does the engine sound louder after changing the coolant?
2 Answers
Replacing the coolant is generally unrelated to the engine. If you genuinely perceive an increase in noise, first check whether it originates from inside the engine or from external components such as the belt, alternator, water pump, or tensioner. Typically, start by ruling out external noise sources. How to choose coolant: The fundamental indicators of coolant are its freezing and boiling points. Market-available coolants come in various freezing points like -15°C, -25°C, -30°C, and -40°C. It's advisable to select a coolant with a freezing point at least 10°C lower than the lowest temperature in your region. Coolant replacement cycle: Vehicle coolant generally needs replacement every 2 years or 40,000 kilometers. This is merely a reference interval. For commercial vehicles with higher mileage, the replacement cycle should be shorter. Since driving conditions vary for each vehicle, the replacement should be based on actual usage. Monitor the coolant's condition—if levels are low, replenish promptly. If suspended particles, sediment, discoloration, or deterioration are observed, replace the coolant immediately and flush the system.
I recently changed the coolant in my car by myself, but after driving, I noticed the engine was humming much louder than usual. A mechanic friend told me it might be due to air bubbles entering the cooling system during the coolant change, especially around the water pump. If the system isn't properly bled, the water pump can cavitate and make strange noises. This is quite common, as both new and old cars require careful handling during coolant replacement. I tried driving for a while to let the system circulate, and the issue improved. If the noise persists, it's worth checking whether the coolant type is correct or if the water pump itself has a problem. Paying attention to these small details during maintenance can prevent bigger issues—don't delay, safety comes first. In short, I learned from this experience to take my time with DIY projects and consult a professional shop if unsure.
