Coolant System Service

Why it matters

Coolant carries heat out of the engine and into the radiator. It is a blend of water, antifreeze, and corrosion inhibitors — and those inhibitors wear out long before the liquid looks bad. Once they are gone, the system starts corroding from the inside, and radiators, heater cores, and water pumps are the usual casualties.

Signs it is time

• Coolant is brown, rusty, or has floating debris in it
• Sweet smell or green or orange puddles under the car
• Temperature gauge climbs above normal in traffic
• Heater blows cold, or the coolant level keeps dropping
• Mileage or age past the interval, often five years or 100,000 miles

If you wait

Overheating warps cylinder heads and blows head gaskets, which turns a service into a teardown. A car that runs hot on a summer climb is a car you cannot trust.