Winter mornings can be challenging enough without the added discomfort of a car heater that’s failing to do its job. If your vehicle’s interior feels more like a fridge than a cosy retreat, a clogged heater core could be to blame.
This small but crucial component of your car’s heating system plays a big role in keeping you warm and your windscreen clear.
Understanding the symptoms of a clogged heater core is essential for your comfort and for maintaining your vehicle’s overall performance. Let’s examine what to look for and how to address this common issue.
What Is A Heater Core?
A heater core is a heat exchanger that radiates heat into a vehicle’s cabin. This heat originates from engine temperature coolant that flows throughout a vehicle’s heater core, via small tube-like passages.
A vehicle’s blower motor forces air across a heater core, dispelling heat through the adjacent duct-work.
As a result, warm air fills a vehicle’s cabin, thereby stopping winter’s chill in its tracks. The end result is a comfortable commute for drivers, even in the face of bitter cold seasonal temperatures.
A heater core features inlet and outlet junctions at a vehicle’s firewall. Coolant lines are affixed at these junctions, courtesy of hose clamps or quick-connect unions.
Some vehicles regulate the flow of coolant through these hoses, by way of a specialty heater control valve. This valve is typically controlled by vacuum, or electrical means, and actuates in response to control head input.
The heater core itself is mounted deep beneath a vehicle’s dash, in close relation to the interior side of the firewall. As a result, heater core-related issues are typically diagnosed by analyzing one or more symptoms associated with the failure at hand.
Therefore, it is extremely important to recognize and understand the various symptoms associated with a faulty or obstructed heater core.
Clogged Heater Core Symptoms
A clogged or defective heater core will display some symptoms to alert the driver and to fix it promptly. Here are some notable signs:
#1. Foggy car interior.
A common sign of a bad heater core is a foggy car. Do your car interior fogs up for no reason? I don’t mean a little moisture on your car windows and windshield. I’m referring to a warm condensation, having all the windows covered with moisture.
A notable cause of this significant moisture is a blown heater core. It could be that the heater core blew up while cruising down the road.
If this component blows up, it’ll cause warm coolant to leak into the car cabin. When the warm and temperature-regulated coolant leaks out, it will evaporate as steam and cause severe fog in the cabin and car interior.
#2. Sweet smell.
Do you perceive an odd smell from the cabin? It’s pretty possible for a heater to leak without fogging up the car windows and windscreen. But it will give a freshly melon smell from the vents.
The sweet smell is coming from the car coolant, which signifies a coolant leak into the cabin. If you perceive this lovely smell outside the car, look around the underneath of the vehicle and see how much coolant loss is under it.
#3. Too much coolant loss.
If you notice too much coolant loss and you can’t figure out where the coolant is going, you may have a leaking heater core.
Unfortunately, if you can’t track down where the coolant is leaking, it is likely happening on the heater core and dripping into the cabin.
If this occurs when the system is cold, instead of creating fog, it’ll form a puddle in the cabin.
Once you suspect a defective heater core, look around the passenger side floor. If the floor mat is wet with a pleasant smell, consider inspecting the heater core.
#4. Cold passenger compartment.
As much as it signifies a defective heater core, it can indicate other system component issues. It could be a symptom of a bad blower motor or other faulty heater components that may be easier to fix than the heater core itself.
In any case, if you experience it with a lack of heat, it is pretty clear that the heater core is the culprit – and should be fixed.
If a puncture or hole exists on the heater core, the warm air in the heater will evaporate before getting to the heater ducts in the car interior. The evaporated air will keep the passenger compartment cool.
Depending on the severity of the puncture, it’ll send lukewarm, mildly warm, or even cold air into the car interior.
#5. Hot engine, But cold cabin.
Is your engine overheating, and you have a cold cabin? If yes, you need to diagnose the state of the heater core.
Do not forget that other system components can contribute to engine overheating. If the heater ducts stop sending in warm air and the engine is running hot, check if there’s a coolant leak within the cooling system.
Overheating can cause catastrophic damage to the engine components. That said, do not allow overheating [no matter how small to linger]. Track down the culprit and fix it as soon as you can.
Always pay attention to your instrument cluster while you journey. If you see your temperature gauge creeping up towards the danger zone, park the vehicle in a safe place.
Find out the fault and fix it before hitting the road. If you can’t fix it, call your mechanic or tow the vehicle to a mechanic garage.
Now, you may be asking, ‘does the heater core affect ac since it can cause overheating?’ No, the heater core cannot prevent the ac from blowing cold air.
What Causes Heater Core To Clog?
There are numerous potential causes of a clogged heater core. While each of these causes differs in origin, all lead to the same troubling condition, which must be remedied in order to restore heater core operation back to peak efficiency.
The following are several of the most common causes of a heater core leak.
#1. Rust/Scale Build-Up.
Corrosion of any type is extremely detrimental to a vehicle’s cooling system as a whole. However, heat exchangers found within this system are especially prone to problems resulting from rust and scale build-up.
This includes the heater core, which tends to clog quite easily. Rust and scale build up of this type often result from the prolonged use of water within a vehicle’s cooling system.
#2. Mixing of Oil/Coolant.
When oil and coolant mix, sludge is created as a byproduct. This sludge quickly spreads throughout a vehicle’s cooling system, including the heater core.
Due to the density of this sludge, clogging often occurs, ultimately slowing or eliminating the flow of coolant throughout the heater core. Gasket failure is by far the most common cause of oil/coolant mixing.
#3. Use of a Stop Leak Product.
Many vehicle owners choose to use various stop leak products to eliminate cooling system leaks of one type or another. However, these products tend to cause clogging within a vehicle’s heater core.
This is especially true when more than the recommended amount of such products are used. Stop leak products can also clog a vehicle’s radiator in a very similar manner.
#4. Restricted Hoses.
Heater hoses are responsible for transferring coolant from the engine to the heater core. These hoses play an important role in maintaining adequate coolant flow, which allows your car’s heating system to work as it should.
Over time, wear and tear, debris, and other factors can cause these hoses to become restricted or even collapsed.
When the hoses become restricted, the circulation of coolant through the heater core may be reduced or even stopped and can lead to the issues mentioned above.
How Do You Test A Heater Core?
Indeed, one of the causes of a clogged heater core or why the heater is sending heat is because you have a defective thermostat.
So, when a heater fails to produce the desired amount of heat, the first thing most technicians do is replace the thermostat before troubleshooting for any other cause.
However, as alluded to above, other factors can cause a lack of heat from the heater ducts. The following few paragraphs explain how to test a heater core.
Step 1
Start and heat the engine: Fill the radiator with the required amount of coolant. Start and run the engine to the average operating temperature. Hold and see if the upper radiator hose is extremely hot to hold.
- If the hose is cold or warm, change the thermostat to a new one.
- Check if the hose has enough pressure. If it doesn’t, replace the radiator cap.
- If everything seems okay, head on to the next step.
Step 2
Feel the heater hoses: Start the engine and allow it to run for a couple of minutes. While the engine is running, set the heat setting to maximum heat and feel the hoses. Both hoses should be very hot to hold, not warm or cold.
If the hoses are hot as they should be, inspect the heater control valve to ascertain if it’s working fine. If one of the hoses is hot and the other is warm, disconnect the hoses and flush the heater core thoroughly.
Step 3
Inspect airflow blend door: If the heater hoses are hot and yet the heater is not sending in warm air, consider inspecting the airflow blend door. Consult your service booklet for direction or seek professional advice.
Note: If heat comes and disappears from the heater ducts, check your coolant level. It is likely a coolant issue. A low coolant level is responsible for causing heat fluctuation from the heater ducts, especially at higher engine speeds.
Pressure Testing
Pressure Testing is a quick and easy means of testing a cooling system for leaks using a hand-operated testing kit.
To use this kit, shut off the engine and allow it to cool down. Remove the radiator pressure cap and attach the kit to the radiator opening. Operate the plunge on the testing kit. By doing so, it’ll pressure the entire cooling system, including the heater core.
However, do not go beyond the manufacturer’s specified pressure. Most manufacturers warn not to exceed 14 PSI (100kpa). Higher pressure can damage the heater core, radiator, water pump, or hoses.
If the pressure kit maintains a certain pressure without dropping, it means there’s no leak in the system components. But if the pressure drops, it signifies a leak in the system. Inspect all the cooling systems for leaks.
Consider centering your inspection on the following areas; cylinder head, radiator, radiator hoses, heater core hoses, heater core, cylinder head, and engine block core plugs.
Pressure testing should only be carried out when there is a suspected leak in the system or when the leak is apparent but you haven’t figured out where it is dropping from. Pressure testing can also be used to diagnose radiator pressure caps.
How to Diagnose a Clogged Heater Core
#1. Inspect hoses and fittings for leaks.
One of the first steps in diagnosing a clogged heater core is to inspect the hoses and fittings for any signs of leaks. Look for wet spots or puddles of coolant under the vehicle or around the engine bay.
Leaks can prevent the proper flow of coolant through the heater core, leading to reduced heat output. If you find any leaks, they will need to be repaired or replaced before further diagnosis can be performed.
#2. Feel temperature at vents after warmup.
After the vehicle has warmed up, check the temperature of the air coming out of the vents. If the air is significantly cooler than it should be, it could indicate a clogged heater core.
A clog can prevent the hot coolant from flowing through the core, resulting in reduced heat output.
This can be a clear indication that the heater core needs to be inspected and potentially cleaned or replaced.
#3. Check coolant color and level.
Another way to diagnose a clogged heater core is to check the color and level of the coolant. The coolant should be a bright, vibrant color, such as green or orange, depending on the type of coolant used.
If the coolant appears murky or discolored, it could be a sign of debris or sediment build-up in the heater core. Additionally, if the coolant level is consistently low, it may indicate a leak or blockage in the system that is affecting the heater core.
#4. Perform pressure tests on system.
A pressure test can help determine if there are any blockages in the heater core or other parts of the cooling system.
By applying pressure to the system, any leaks or restrictions can be detected. This test should be performed by a qualified technician who has the necessary equipment and expertise.
It can provide valuable information about the condition of the heater core and help identify any potential clogs.
#5. Use a borescope to view inside core.
In some cases, it may be necessary to use a borescope to visually inspect the inside of the heater core. A borescope is a flexible tube with a camera that can be inserted into tight spaces to capture images or videos.
By examining the interior of the heater core, any blockages or obstructions can be identified. This method is often used when other diagnostic methods have been inconclusive.
Tools and Materials You’ll Need
- Socket wrench set
- Screwdriver set
- Pliers
- Drain pan
- Coolant flush kit (optional)
- New heater core
- Coolant
How To Unclog A Heater Core
1. Safety First: Park your vehicle on a level surface, engage the parking brake, and allow the engine to cool completely.
2. Locate the Heater Core: Refer to your vehicle’s service manual to determine the location of the heater core. It’s typically situated behind the dashboard or beneath the center console.
3. Disconnect the Hoses: Using pliers, carefully loosen the clamps securing the heater hoses to the heater core. Allow the coolant to drain into a drain pan.
4. Remove the Heater Core: Using a socket wrench, remove the bolts or screws holding the heater core in place. Gently pull the heater core out of its housing.
5. Inspect the Heater Core: Examine the heater core for any visible blockages, such as debris or scale build-up. If it’s severely clogged, you may need to replace it.
6. Clean or Replace the Heater Core: If possible, attempt to clean the heater core using a water hose or a commercial cleaning solution. If the core is beyond repair, install a new one.
7. Reassemble: Insert the new or cleaned heater core into its housing and secure it with bolts or screws. Reconnect the heater hoses and tighten the clamps.
8. Fill and Bleed the System: Fill the radiator with coolant and top off the overflow tank. Start the engine and allow it to run until the thermostat opens. Use a radiator flush kit to remove any remaining air from the system.
Heater Core Flush Cost
In certain instances, a clogged heater core can be flushed, thereby restoring a vehicle’s heating efficiency. In other cases, a heater core must be replaced, as efforts to alleviate a clog through flushing, have proved futile.
In any event, it costs significantly less to flush a heater core, than it does to replace the affected heater core in its entirety.
This is due to the significant amount of time that is required to replace most heater cores and the labor cost that such an expenditure of time commands.
In general, a heater core flush typically costs somewhere in the neighborhood of $75-$100. However, this price also varies depending upon the make and model of the vehicle in question, as well as one’s choice of service center.
For actual cost, contact the dealership or service center that has worked on your car in the past or simply Google “heater core flush near me” and obtain at least a couple estimates from local mechanics.
Heater Core Replacement Cost
In the event that a traditional heater core flush yields no results, and you are still left without sufficient heat, heater core replacement might be necessary.
This, unfortunately, is an expensive proposition. Due to the heater core’s location deep within a vehicle’s dash, much time and effort are required for removal.
As such, the labor costs associated with heater core replacement tend to be quite extensive. However, the exact price of these repairs can vary greatly from one model of vehicle to the next.
Most shops charge for the number of labor hours specified by a vehicle’s manufacturer when completing repairs. In certain cases, heater core replacement can require as much as 7-8 hours of labor.
On average, heater core replacement costs approximately $750-$1,100. This includes both the cost of a heater core itself and the labor associated with installation.
The lower end of this price spectrum reflects replacement with relatively cheap parts/labor, while the higher cost is representative of replacement in a dealership setting, with the use of OEM components.
Will a radiator flush unclog the heater core?
The radiator and heater core are two different components that perform similar but different functions. Yes, they are both cooling system components, and the same coolant travels through them.
Flushing a radiator can help reduce the rust that passes through the heater core. The most effective way of unclogging a heater core is by flushing it with a garden hose. Scroll up to see the guides on how to fix a clogged heater core.
FAQs.
Q: Can a clogged heater core cause overheating?
Apparently, a clogged heater core has a slight tendency to cause engine overheating. Did you notice I said a slight tendency? This means, in most cases, it won’t cause engine overheating, while in some instances, it can compromise the cooling system.
There are several other factors that you should look into when your engine overheats. However, if you have a clogged heater core and your engine temperature is running high, it’s best to flush the heater core.
Q: Can you drive with a clogged heater core?
As much as you can still drive with a clogged heater core, do not journey with it as it can cause the engine to overheat and damage engine components. A clogged heater core can reduce coolant circulation, which will cause the engine to run at a higher temperature.
In any case, if you decide to continue driving with a clogged heater core, keep your eyes on the temperature gauge.
You can also decide to bypass the heater core but before doing this, find out the side effects of bypassing a heater core.
Q: Will Vinegar clean a clogged heater core?
Vinegar is a liquid containing 5% acetic acid, and it’s perfectly okay to remove rust in cooling system components like radiator and heater cores.
To unclog a heater core with vinegar, pour a gallon of vinegar into the system and run the engine for 15-20 minutes with the heater on.
Q: Can you fix a heater core without replacing it?
The heater core location makes it easier to fix than to replace. The heater core can be sealed off by pouring radiator-stop leak products into the radiator when it is cool.
There are numerous stop-leak products in the market. However, I recommend using Blue Devil Pour-N-Go or Simple Green stop leak for an excellent job.
Q: How much does it cost to get a heater core flush?
Replacing is a tedious job and requires a mechanic to do it because of its position.
On the other hand, flushing a heater core is an easy job that anyone can do provided the instructions, and the unclogging kit is at their disposal.
However, if you don’t have the time and kits needed to flush it, getting it done by a mechanic will cost around $100 to $200.
Q: How much is a heater core replacement?
Replacing a defective heater core can be an expensive repair, costing up to $550 to $100. The replacement parts are usually cheap and fall within the range of $70 to $200, but the labor due to the location and repair hours involved tend to be pretty high.
Final word
Now that you’re familiar with clogged heater core symptoms, causes, problems, diagnosis, and how to fix it, you can easily flush or unclog your heater core whenever it develops issues.
The diagnosis and unclogging procedures explained in this article are easy to follow. Nonetheless, if you still don’t feel comfortable doing it yourself, seek professional assistance.