A heater core is much like a small radiator. Coolant is circulated through it from the water pump, and it has fins to increase the surface area and shed heat more efficiently. The heater core is located in the HVAC box (which stands for heating, ventilation, and air conditioning), which is typically located on the firewall in the vehicle’s passenger compartment. In order to gain access to the heater core, the box typically needs to be disassembled, which in many cases involves the complicated job of removing the dash. In most cases, it’s an all-day job, at least.
Signs that a heater core needs to be replaced are:
- Coolant loss, often visible at the HVAC box drain under the engine firewall area.
- The smell of coolant in the cabin, and sometimes greasy-feeling fogging on the lower windshield above the defrost vents. Wet carpet under the dash on the passenger side.
- No heat will come from the vents, if the heater core is blocked.
Costs of Heater Core Replacement
On average, it costs about $1,200 to replace the heater core in most vehicles.
For some more specific estimates of the cost of heater core replacement, using $150 an hour as a labor rate and adding in the cost of a couple of gallons of coolant:
For a 2003 Honda Civic with a 1.7-liter engine, the labor time to replace the heater core is 7.3 hours. A factory heater core lists for $396, and a UAC part costs about $97. This makes the job about $1520 using OE parts, or about $1232 using aftermarket parts.
For A 2006 Ford Fusion with a 3.0-liter engine, the labor time to replace the heater core is 5.6 hours. A factory heater core lists for $133, or an OSC part costs about $90. This makes the job about $1013 using OE parts, or about $970 using aftermarket parts.
For a 2009 Nissan Frontier with four-wheel drive, the labor time to replace the heater core is 6.6 hours. A factory heater core lists for $417, or a GPD part costs about $75. This makes the job about $1450 using factory parts, or about $1100 using aftermarket parts.
For a 2002 Dodge Intrepid with a 2.7-liter engine, the labor time to replace the heater core is 5.8 hours. A factory heater core lists for $271, and a UAC part costs about $90. This makes the job about $1180 using OE parts, or about $1000 using aftermarket parts.
For a 2003 Honda Civic with a 1.7-liter engine, the labor time to replace the heater core is 7.3 hours. A factory heater core costs about $341, or a UAC part costs about $65. This makes the job about $1081 using OE parts, or about $815 using aftermarket parts.
What Goes Wrong with Heater Cores?
The most common cause for replacement is a heater core leak. They are necessarily made out of thin metal to transmit heat most effectively, and they can be delicate. Vibrations or physical handling can cause a heater core to crack and leak, or it can also leak from corrosion. Their location in the vehicle is pretty well protected from external corrosives, but if the fluid in the cooling system is aged or contaminated, it can corrode internally. The thinness of the metal can make the heater core the first thing to leak in that case.
Another reason to replace the heater core is if the core becomes plugged. In most cases, a plugged heater core can be flushed. It only takes a little bit of obstruction to reduce coolant flow to the point that the heater doesn’t work, and the procedure then is usually to pull the heater hoses and flush clean water through the core back and forth until it runs clean and freely. That doesn’t always work, though, and then replacement is the next step.
Clogs can happen because the fluid is old or contaminated, or sometimes they can be caused by stop-leak products, which can clog small passages in the radiator and heater core. Another issue is that some different types of coolant are incompatible; when mixed, some combinations can congeal into a thick gel that is very difficult to clear from fine coolant passages. In that case, the heater core is one of the first parts affected, and it is usually replaced.
What else can seem like a bad heater core?
If the coolant level is low for any reason, air can be introduced into the coolant system. The heater core is often the high point in the cooling system, and it is prone to trapping air in many vehicles, which prevents coolant flow and reduces heater function. Ruling out air in the system is one of the first steps if the heater doesn’t work well; using a vacuum device is the most common way of doing that in shops.
There are blend door actuators that control airflow in the HVAC box. If a blend door actuator goes bad, that can prevent airflow across the heater core and prevent the heater from working. That can be mistaken for a plugged heater core.
There is a heater control valve that opens or closes to control coolant flow through the heater core. If the valve fails, that can prevent flow through the heater core, which can also be mistaken for a plugged heater core.
- How can I avoid heater core problems?
The main way is to service the coolant according to the schedule in the owner’s manual and to make sure that nothing but the correct fluid is added to the cooling system. If water must be added, most manufacturer’s recommend using distilled water rather than tap water.
- Can I drive without a heater core?
Yes, though that’s more or less a problem depending on the weather if the core is plugged. If the core is leaking, the heater hoses can be blocked off to isolate the leaking heater core. But there will be no heat or defrost functions in the vehicle then.
- How long does it take to replace a heater core?
In most cases, it’s close to an all-day job, sometimes even involving disassembling and removing the dash.
- How long should a heater core last?
Barring manufacturing defects or poor maintenance, it should last the life of the vehicle.
- Can I replace my own heater core?
Probably not. In many cases, the AC needs to be evacuated and then restored afterwards, which requires special tools and training. And there are so many easily broken and complex things to be dealt with during replacement that it can be frustrating even for a seasoned mechanic.