One of the most common problems that can happen to a vehicle is a heater core leak. A leaking heater core is not a breakdown risk (although you do need to monitor the coolant level). It can cause damage to the vehicle in other ways, and should be addressed as soon as possible.
How a Heater Core Works
A heater core is a little radiator that runs hot coolant to the inside of the vehicle. It works exactly like the radiator does. There is a line of hot coolant coming from the engine, and there is a return line.
The blower motor runs air over the heater core and the cabin warms up. Temperature is controlled by the blend door, which the driver controls. The more the heat is turned up, the higher the percentage of air passing over the heater core.
Bad Heater Core Symptoms
1. Coolant Smell
The nose and ears are our best auto diagnostic tools. You can learn a lot about what is going on with a vehicle by what smells and sounds different. In the case of a bad heater core, the smell you’ll be smelling is quite sweet. It’ll smell like maple syrup or fruit. Really, it’s whatever your engine coolant smells like.
2. Coolant in the Cabin
If you are able to easily smell coolant while driving the vehicle, you’ll probably be able to find coolant on the floor. A heater core that is slowly leaking will do damage to the sheet metal under the carpet.
The heater core is itself is almost always located on the passenger side of the vehicle. Turn on the blower motor and follow the sound. They are always close to one another. Check the floorboard directly below the heater core and see if it is wet. If coolant is allowed down there for a very long time the floorboards can rust.
3. No Heat
If your vehicle doesn’t have any heat at all, that can be a sign of a bad heater core. It could also be a sign that you are almost out of coolant. If coolant can’t get to the heater core, it won’t produce any heat at all.
In the case that the heater isn’t putting out heat, check to make sure that the coolant level is full. You shouldn’t need to pull the radiator cap off, just check the overflow and fill it up. If it’s bone dry fill it up and let the cooling system pull it in as the car/truck warms up.
It is also possible that the blend door isn’t opening or closing properly. Depending on how old and complicated the vehicle is, the blend door may be operated by cable, or it could be operated by an actuator. It’s not unheard of for them to freeze up and not work until thawed back out.
4. Foggy Windows
Foggy windows are a sure sign of a bad heater core. When you turn the heater on, and the heater core is bad, it’s effectively acting as a humidifier. Except that’s not water causing the fog, it’s antifreeze.
Antifreeze is harmful and can be fatal if swallowed. It’s not good to breath as a vapor either.
5. Overheating
An overheating engine can indicate that the heater core is leaking. But, there are a lot of other reasons why a vehicle could overheat. In fact, if you are overheating don’t start with the heater core unless you are getting obvious signs from inside the vehicle.
Bad Heater Core Causes
A bad heater core is going to be caused by a crack that leaks coolant out, or it’s going to be clogged. When it is clogged it doesn’t have a leak, but it also won’t provide heat to the cabin.
Conclusion
Good luck determining whether or not your heater core is bad. If there is anything that you would like to add, please feel free to leave a comment below.