What You Need to Know About Coolant and Antifreeze

Coolant serves two distinct functions: it prevents the engine from freezing in Indiana winters, and it prevents the engine from overheating in Indiana summers. It also contains corrosion inhibitors that protect the aluminum, copper, and steel components of the cooling system from chemical attack. When coolant degrades and its corrosion inhibitors are depleted, cooling system components corrode from the inside out in ways that are not visible until they fail.

Understanding Coolant Types

The automotive industry has moved through multiple generations of coolant chemistry. Older green conventional coolant uses inorganic additive technology and needs replacement every two years. Modern long-life coolants using OAT (Organic Acid Technology) or HOAT (Hybrid OAT) formulations last five years or more and come in various colors including orange, pink, yellow, blue, and red depending on the manufacturer. Using the wrong coolant type for your vehicle can cause incompatibility with existing residual coolant and accelerate corrosion rather than preventing it.

What Degraded Coolant Does

As coolant ages beyond its service life, its corrosion inhibitors deplete. Depleted coolant allows the slight acidity of the water-coolant mixture to attack aluminum components including the radiator, heater core, and water pump housing. Corrosion products circulate through the system, clogging the small passages in the heater core and radiator. Heater core replacement is a labor-intensive repair costing $500 to $1,200 on most vehicles because the dashboard must be partially disassembled for access.

Checking Coolant Condition

Coolant condition can be checked with a simple test strip available at auto parts stores. The strips test pH and freeze protection. Coolant that has turned from its original color to rust brown or has debris floating in it is significantly degraded and should be replaced promptly. A cooling system flush at an independent shop costs $80 to $150 and is one of the better-value preventive maintenance services available.

Never Open a Hot Radiator

Cooling systems operate under pressure and can reach temperatures above 200 degrees Fahrenheit. Never open the radiator cap or overflow reservoir cap on a warm or hot engine. The sudden pressure release can cause scalding coolant to spray. Wait until the engine has cooled completely before checking or adding coolant.