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What Causes Sludge in Radiators?


Sludge. It’s that thick, brown-colored substance you see when you open the cap on your car’s radiator. You tend to notice it more after the engine has overheated. Unfortunately, the engine probably overheated because of sludge build-up. Since one of the leading causes of roadside breakdown is cooling system failure, pay particular attention to the condition of your radiator.


Corrosion is the most common cause of sludge build-up in a radiator. Radiators are made of metal. Over time, antifreeze degrades. As it loses its protective qualities, PH levels change and corrosion sets in. Once this begins, rust, sludge and scale build up through the entire cooling system, including the engine. The sludge can block the flow of coolant, causing the engine to overheat and leak. If left untreated, overheating and leaking can lead to very expensive repairs.