As winter approaches, it’s about time not to take a working heating system for granted. When those cold temperatures come and you discover your heater core is clogged, it makes your drive that much worse.
The heater core is a vital component of the heating system, and it regulates how much heat goes into the cabin, so if a heater core is blocked or clogged, then you are going to be without heat.
Continue reading to learn about the common symptoms of a clogged heater core, what can cause a clogged heater core, and how much it will cost to flush or replace a heater core.
What is a Heater Core?
A heater core is a heat exchanger that releases heat into the cabin of a vehicle. Heat comes from the engine temperature, coolant flowing through a heater core, via small tube-shaped passages.
A vehicle’s blower motor pushes air across a heater core, releasing heat, through ductwork immediately adjacent to the heater core.
This displaces cool air, producing warm air in a cabin, thereby ceasing winter’s chill and the imagined inconvenience of a cold commute, as such heated air qualifies the experience of any driver, even in cold seasonal temperatures.
A heater core has inlet and outlet junctions at a vehicle’s firewall. One set of coolant lines attached here, to junctures, was made by hose clamps or quick-connect unions.
Most vehicles will control the amount of coolant through these hoses by using a heater control valve. These valves will be vacuum actuated or controlled by electrical means, based on control head input activation.
The heater core is mounted below a vehicle’s dash, and close to the interior side of the firewall. Therefore, heater core diagnosis is usually based on observing or evaluating one or more symptoms of the failure in question.
It is therefore important to know and understand the heater core symptoms of failure or heater core blockage.
Signs of a Clogged Heater Core
There are a number of signs that tend to coincide when there is a clog in a vehicle’s heater core. The signs associated with this kind of failure are often different on an individual basis, but there are a few signs that are more common on average.
Here are a few of the most prevalent signs of a clogged heater core or a bad heater core.
#1. No Heat.
The most frequent sign of a clogged heater core is lack of heat. If coolant cannot flow through a vehicle’s heater core, the capacity to heat is severely limited. So it’s best in this situation to expect a pretty cold ride, with no relief from your disabled heating core.
#2. Weak Heat in Extreme Cold.
In some situations, your vehicle might be able to produce enough heat during mild cold weather, but be weak whenever extreme cold weather sets in. This is a sign of either a partially clogged heater core or the ability to heat is somewhat compromised.
On these occasions, there is enough heat flowing into the heater core, but the overall capacity has been compromised. In this case, flushing the system will make it usable again.
#3. Possible Overheating.
Can a bad heater core cause overheating? For the most part, the clogged heater core on its own will not cause overheating. When taken in conjunction with other issues, then it could cause the engine to overheat.
This is often the case when cooling system efficiency is already impacted, such as with a bad water pump or a clogged radiator.
#4. Foggy Windows.
One of the first signs you can notice in cool weather is foggy windows. When the heater core is not functioning as it should. It can’t provide enough heat to the cabin, and condensation starts to build up on the inside of the windows. It could even turn into frost on the inside of the windshield.
This level of fogging will persist and not just a couple of minutes of warming your vehicle. Keeping this symptom persistent will make visibility difficult while driving, which means exercising caution.
#5. Wet Carpets.
Not very common, a clogged heater core may leak coolant, which can then work itself into the interior of the car and potentially dampen the carpets in the vehicle. This can also lead to bad smells and potential mold.
Look for the moisture in the vicinity of the passenger footwell, as it’s common to see heater core leaks seep in this area.
What Causes a Heater Core to Clog?
There are many potential causes of a clogged heater core. While all of these causes are different, they all create the same problem, which has to be fixed in order to bring heater core performance back to optimum performance level.
Listed below are several of the most common causes of a heater core leak.
#1. Rust/Scale Build-Up.
Corrosion of any kind is incredibly harmful to a vehicle’s cooling system in totality. However, heat exchangers found in this system are especially vulnerable to issues caused by rust and scale building up.
This includes the heater core, which has a predeliction to clog up easily. This rust and scale build up is usually caused by prolonged effects of using water in a vehicle’s cooling system.
#2. Oil/Coolant Mixing.
When oil and coolant mix, the byproduct that is created is a sludge. This sludge gets circulated in a vehicle’s cooling system, including the heater core.
This sludge clogs the heater core because of the density, slowing down or even stopping coolant flow in the heater core. Gasket failure is the single most common culprit for oil/coolant mixing.
#3. Use of a Stop Leak Product.
A lot of vehicle owners use various stop leak products to stop leaks in their cooling system, depending on the type of leak. These stop leak products also clog a vehicle’s heater core.
This happens, especially, if more than the required amount of stop leak product is used. Stop leak products can clog a vehicle’s radiator in the same fashion as well.
#4. Restricted Hoses.
Heater hoses transfer coolant from the engine to the heater core. These hoses play a vital role to keep coolant flowing to get heating needs met in a vehicle.
Hoses will wear out eventually, they will get clogged up with debris, etc. and can get restricted or totally collapsed.
When they get restricted, circulation through the heater core could get reduced or stopped, and cause the issues mentioned above.
Heater Core Flush Cost
In some situations, a clogged heater core can be flushed, restoring a vehicle’s heating ability. In other situations, a heater core must be replaced instead. Flushing does not always relieve the clog.
In any case, a heater core flush costs substantially less than replacing the heater core entirely.
It costs less because replacing most heater cores takes a considerable amount of time and time is expensive when billed as labor.
Generally, flushing a heater core costs in the ballpark of $75-$100. However, this price may vary based on the vehicle’s make and model, as well as the type of service place.
For actual cost, please contact the dealership or service place that has been working on your car in the past, or simply Google “heater core flush near me” to obtain at least a couple of estimates from local mechanics.
Heater Core Replacement Cost
If a conventional heater core flush produces no heat and you are still freezing, a heater core replacement may be required. Regrettably, heater core replacement is not cheap.
In order to replace a heater core, the heater core is located deep inside the dash of the vehicle, which takes a long time to be removed. Because of this, labor on heater core replacement is usually very high. However, the repair cost can vary significantly between vehicle models.
Most shops charge based on the labor hours the manufacturer built into their repair time. Replacement of the heater core can take upwards of 7-8 hours of labor in some instances.
The average heater core replacement costs in the vicinity of $750-$1,100. This includes the price of the heater core and the labor to install it.
The lower range of the price reflects replacement with cheaper parts/labor, while the higher price in the range reflects the replacement in a dealership, with OEM components.
How to Bypass the Heater Core
At times, bypassing the heater core is a temporary solution when you have a clogged or leaking heater core. Below are instructions on how to accomplish this:
#1. Locate the Heater Core Hoses.
Locate your two hoses that connect to your heater core at the firewall in your engine compartment. Typically, the two hoses will be the same size, and they will both run from the engine to the passenger compartment.
#2. Disconnect the Hoses.
Carefully disconnect the hoses from the heater core. Be aware of any coolant that may spill. Remember, coolant can be hot and burn you!
#3. Connect the Hoses Together.
Use a compatible connector to connect your two hoses. Ensure the connector is a tight fit or does not leak at the connection.
#4. Secure the Hoses.
Use hose clamps to securely connect the hoses to the connector. Enter the connector to be tightly fitted and leak-free.
#5. Test the Bypass.
Start your engine and allow it to heat up to operating temperature. Now check the connection for leaks and allow coolant to circulate through the hoses.
A heater core bypass is not a permanent fix and should not be used for that purpose.
Regardless, for now, circumventing a heater core will prevent further damage to your engine due to clogged or leaking heater cores. However, this solution does turn off the heat in your vehicle!
As with any car issue, you should fix the real problem, then repair or replace the heater core when you can get to it to restore the heating functionality.