A heater core is quite 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 placed 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. To access the heater core, the box usually 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 replacement are:
- Coolant loss, often from the HVAC drain around the firewall area.
- The smell of coolant in the cabin, and sometimes greasy-feeling mist on the lower windshield from the defrost vents.
- No heat from the vents if the heater core is blocked. To rule out temperature blend door issues, which can cause the same problem, usually the heater hose temperatures are checked. If coolant is flowing through both hoses, they will be the same temperature and hot.
Costs of Heater Core Replacement
On average, it costs about £700 to replace the heater core in most vehicles.
For some more specific estimates of the cost of heater core replacement, using £70 an hour as a labour 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 labour time to replace the heater core is 7.3 hours. A factory heater core costs around £300, or an OEM-compliant part costs about £55. This makes the job about £800 using OEM parts, or about £570 using aftermarket parts.
- For a 2006 Ford Fusion with a 3.0-liter engine, the labour time to replace the heater core is 5.6 hours. A factory heater core costs about £145, or an OEM-compliant part costs about £55. This makes the job about £530 using OEM parts, or about £450 using aftermarket parts.
- For a 2009 Nissan Frontier four-wheel drive, the labour time to replace the heater core is 6.6 hours. A factory heater core costs about £300, or an OEM-compliant part costs about £75. This makes the job about £750 using factory parts, or around £540 using aftermarket parts.
- For a 2002 Dodge Intrepid with a 2.7-liter engine, the labour time to replace the heater core is 5.8 hours. A factory heater core costs about £145, or a compliant part costs about $60. This makes the job about £550 using OEM components, or about £460 using aftermarket parts.
What Goes Wrong with Heater Cores
The most common cause for replacement is a heater core leak. They are generally made from 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 well protected from external corrosives, but if the fluid in the cooling system is aged or contaminated, they 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 to 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.
The main ways are 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 manufacturers recommend using distilled water rather than tap water.
Yes, though that’s mostly a problem depending on the weather. The heater hoses can be blocked off to isolate a leaking heater core. But there will be no heat or defrost functions in the vehicle then.
In most cases, it’s almost an all-day job, which sometimes involves even disassembling and removing the dash.