Heater Core Repair: What It Is and When It Fails

What is a heater core?

The heater core is part of your cooling system. It looks like a small radiator. Hot engine coolant flows through it, and air blown across it warms the cabin and powers the defroster. In most vehicles it sits behind the dashboard, inside a housing.

Signs of a failing heater core

• The windows suddenly fog up with a greasy film
• A sweet smell inside the car, which is coolant
• Coolant loss with no visible leak under the hood
• Damp carpet, often on the passenger side
• A heater that blows cold air, though other problems can cause that too
• An overheating engine if coolant has been lost

Why it takes time

Because the heater core is deep inside the dashboard on most vehicles, replacement can mean removing much of the dash and takes several hours. A plugged core may sometimes be flushed, but a leaking core generally needs to be replaced.

Do not ignore it

A leaking heater core loses coolant, which can lead to overheating. If the temperature gauge climbs or a warning light comes on, pull over safely and shut the engine off. Do not keep driving an overheating engine. Have the vehicle towed in. Coolant is toxic, so wipe up spills and keep it away from children and pets.

Next step

Our ASE-certified technicians can inspect your vehicle and explain your options. Book at whichever of our shops is most convenient.