How to Perform a Heater Core Flush Like a Professional Mechanic

One way to ensure a healthy vehicle is by performing a routine heater core flush. If you don’t know what that is, then keep reading.

All cars need maintenance, and this includes scheduled flushes to keep them working properly and running smoothly.

If you notice that your car is starting to overheat, or you notice that there’s no heat at all, something may be wrong. These are issues that should not be ignored, especially if you want your car to live a long and happy life, full of safe trips.

One way to ensure a healthy vehicle is by performing a routine heater core flush. If you don’t know what that is, then keep reading. 

How Will I Know if I Need a Heater Core Flush?

There are a few telltale signs that your car needs a heater core flush. Heater core issues are unique, especially since one of those potential issues is the leaking into your interior. 

Typically when heater core problems present themselves, it’s due to poor cooling system maintenance. You should be flushing and replacing your coolant accordingly with your owner’s manual. This will help to prevent the build-up of dirt, debris, and rust particles in the narrow passages—which ultimately causes clogs and damage.

Here are some of those telltale signs:

  1. Your car doesn’t seem to warm up. It runs fine, the temperature gauge reads normal, and there are no other coolant system issues. Except for the lack of heat when you turn the heat on.
  2. There’s an unknown, sweet fragrance inside your car. That’s the smell of coolant, and it’s probably lightly spraying into your interior. This is an early warning sign.
  3. Your windows fog up. If your cooling is spraying for long enough, it could coat your windows. The residue is hard to clean off, and breathing in ethylene glycol is pretty bad for your health.
  4. Something’s leaking from under your dashboard. If you notice front carpet stains or dripping from under the dashboard, it’s coolant leaking into your car. 
  5. Your engine is running hot. If this is the case, check your coolant level. If it’s running low and your temperature gauge is running high, you’re going to want to get to a mechanic.

If you’re not handy with mechanics, a heater core replacement can cost up to $950 give or take. Which is why you’ll want to perform regular heater core flushes so that you can avoid the high heater core replacement cost. And breathing in poison.

Step-by-Step Heater Core Flush

A heater core flush is something that you can absolutely do yourself, even if you’re not mechanically inclined. Here’s what you’ll need to get started:

  • A large bucket
  • Clear tubing
  • Gloves
  • Pliers
  • A screwdriver
  • A garden hose 
  • An air compressor*
  • A 3/4″ barb fitting adapter
  • rags
  • safety glasses
  • Irontite products

 *An air compressor isn’t 100% obligatory, however, it is extremely helpful in loosening up any gunk before performing the flush. 

If you’re using Irontite products for flushing, coating, and sealing, you’ll want to read the directions thoroughly before beginning this process.

Now, here’s how to perform a heater core flush:

Step 1: Locate the Heater Core

First thing’s first. You’re going to want to find the heater core. It will be located on your car’s firewall. There will be an inlet and outlet hose, one that takes in the coolant and the other which pushes it back out. You’ll want to trace them back to the engine.

If you’re having trouble, refer to your owner’s manual.

Step 2: Disconnect the Heater Hoses

Once you’ve located the heater core and the hoses, disconnect them from the firewall. They’re bound by clamps, which will you’ll need pliers to squeeze or a screwdriver in order to loosen them. 

Before you loosen them, make sure you set your large bucket underneath. Once you’ve removed the clamps and hoses, the coolant will begin to leak out. You’ll want to catch it all and dispose of it appropriately since it’s bad for the environment.

Step 3: Apply the Pressure

If you were able to get your hands on an air compressor, now is the time to use it. You’ll want to make sure that you hook it up to the outlet hose and seal it with a coupler or some duct tape. 

This will enable you to build up pressure, loosening any gunk and tough clogs. You should “pressurize” the heater core for up to ten minutes for the best results. Once enough pressure has built up, you can shut off the compressor.  (Caution: Too much pressure could cause damage. Most systems can easily withstand 20 to 40psi so to be safe you don’t want to exceed that much pressure.)

Before you remove your makeshift compressor hook up, let everything drain, keeping an eye on the bucket to see that it doesn’t overflow. 

Step 4: Hit it with the Hose

Once everything seems to have drained, you can remove the air compressor and attach the water hose using the same sealing method. Turn on the hose and let the flushing begin.

Once the water runs clear, you’re done flushing. Of course, you may want to repeat the entire process twice to ensure success. Once all the water has drained, you can use the air compressor to get rid of any excess water.

Step 5: Reconnect the Heater Hoses

Once you’ve successfully flushed and dried your heater core, you’ll want to reattach the hoses. It’s a good idea to have extra clamps on hand in case the old ones break. Make sure the hoses are back on properly and sealed with the clamps.

Step 5a: Flush your entire cooling system with Thoro-Flush

At this point, it’s not a bad idea to take your efforts one step further and now do a full flush of your entire cooling system using a good quality chemical flush. Irontite Products Thoro-Flush is one of the most powerful of the available flush making it a good choice to get your entire cooling system all cleaned out. Here is a good article on how to flush your car.

Step 6: Refill the Coolant

Now you can begin to refill the coolant in your heater core system. You can do this by removing the radiator cap and pouring your coolant mixture (preferably a 50/50 mix of pure antifreeze and distilled water) into the reservoir on the radiator. 

This part can be a bit of a process, as you’ll have to run your car and let the coolant mixture flow through the system while also burping the coolant system. Burping will allow trapped air to be released. Air in the system can cause overheating. 

Don’t Forget Your Irontite Products

Older vehicles need a little more TLC, especially when flushing the system. Irontite offers some of the best flush and sealant products on the market. This includes Thoro-Flush, All-Weather Seal, and Ceramic Motor Seal. You can use them separately, or combined for the best results.

If you have any questions about Irontite’s products or need a recommendation of which to use, feel free to contact us for our professional opinion.

6 Problems You’re Likely to Experience with Your Engine Coolant System

Proper car maintenance involves understanding all the possible car problems. Here are engine coolant system problems your car might have at some point.

There are 13 phobias that affect drivers of cars and their passengers. If you avoid opening the hood of your car or looking underneath, you may suffer from one of them.

Mechanophobia is the fear of machines. Technophobia is the fear of advanced technology or complex devices. Your car is a machine and depending on how old it is, it might be a complex device. 

But that’s not an excuse for ignoring your vehicle and letting the engine overheat.

Treatment for phobias includes knowledge and desensitization. We’ve put together a guide to 6 of the most common problems people experience with their engine coolant system.

It’s up to you whether you ever open the hood but at least study up on what could go wrong with one of your vehicle’s major systems, the engine coolant system.

1. Old Engine Coolant Syndrome

Okay, there isn’t any such thing as old coolant syndrome. But cars do experience problems when owners don’t change the anti-freeze, or coolant, on a regular basis. 

Coolant doesn’t deteriorate overnight, or even in a month but it does get more acidic over time. Acidity causes coolant to lose it’s anti-corrosive, or rust-inhibiting properties

The result? Damage to your radiator, water pump, radiator cap,  and radiator hoses. Corossion can also damage other parts of the cooling system.

Ultimately, you may find yourself on the side of the road with your engine overheating.

The remedy? Check your engine coolant at least every 50,000 miles and if you notice signs of rust or corrosion, don’t ignore them.

2. Thermostat Gone Bad

Count yourself lucky if all you ever repair on your car is a bad thermostat. They’re relatively inexpensive and one repair most car owners can take care of themselves, even technophobes.

The thermostat is a heat-sensitive control normally located on top of the engine near the radiator hose.  When engine temperature reaches the normal operating temperature, the thermostat opens and allows coolant to flow from the radiator into the engine.

If you have a bad thermostat, it may remain closed, preventing coolant from getting to the engine and keeping it cool. If the thermostat is stuck closed, antifreeze won’t flow and the car overheats.

The thermostat is one of the first things you should check when you see your dashboard temperature gauge move into the red zone.

3. Worn Radiator Hose

A rogue thermostat may be the easiest problem to fix, but a worn out radiator hose is the most common cause of automotive cooling system problems.

Most cars have two radiator hoses. The upper hose runs from the top of the radiator to the top of the engine. The lower hose runs from the bottom of your radiator to the water pump.

Radiator hoses move coolant to the radiator for cooling and then back to the engine. This back and forth process doesn’t only prevent overheating, it also keeps the engine from running too cold.

Radiator hoses are tough. They’re designed to hold up under high heat and pressure. But over time they do crack or get soft.

Replacing a worn-out hose isn’t a major ordeal and with the right tools and a small dose of bravado (for the mechanophobic), it shouldn’t take long for the repair.

4. Radiator Leak and Cracks

Remember the dirty old coolant? It can load your radiator up with sediment. A dirty radiator may cause overheating in the engine.

Interesting tip: Hard water can also cause radiator corrosion. Don’t use your garden hose to refill your radiator.

A crack in the radiator also poses a significant problem. Cracks happen for a variety of reasons:

  • Rust
  • Faulty thermostat
  • Heat
  • Cold
  • Road debris

A cracked radiator leaks engine coolant. Your car won’t let you ignore a radiator problem. You’ll either see a puddle underneath the vehicle, or the car will start running hot.

Some radiator leaks aren’t so easy to pinpoint. You’ll need to check the radiator thoroughly with attention to the bottom and the radiator seams.

Be aware (and thankful) that a cracked radiator doesn’t always need replacing. Often you can prevent problems by doing a radiator flush. You can also use a product designed to seal up radiator leaks.

Another cause of radiator cracks is a leaking head gasket.

5. Do You Have a Blown Head Gasket?

If you ignore your engine’s cries for help and let it overheat one too many times, you could end up with a blown head gasket.

Or the blown head gasket may be the cause of engine overheating. Avoid addressing the issue and you may end up with a costly repair.

One sign of head gasket failure is white exhaust smoke paired with the sweet aroma of burning engine coolant. Loss of engine power is another sign and so is sludge on the oil dipstick or underneath the oil filler cap.

Don’t panic if you think you have a leaky head gasket. Like other cracks and leaks in the cooling system, you can use a sealant on a head gasket.

Fun fact: That sludge on the dipstick is often called a milkshake.

The last item on the list of potential cooling system problems is a failed water pump.

6. Water Pump Failure

You can use special products for sealing most leaks in your engine cooling system. You can probably even drive for a few more miles with a bad thermostat or a weak radiator hose.

If your water pump fails, you should not drive one more mile.

The water pump plays such a vital role in your cooling system that if it stops working, you may end up with a complete engine failure.

Water pumps generally give you at least some warning of the pending doom. You may notice a coolant leak toward the front of the vehicle. You might hear noise—specifically, a grinding or growling sound.

Overheating is another signal and steam or smoke pouring from under the hood usually means you’ve ignored the signs for too long.

Ready to Get Under the Hood?

Caring for your engine coolant system shouldn’t be an ordeal. You don’t need a certification in auto mechanics either.

From the smallest problem of a bad thermostat to the bigger issues of cracked radiators, blown head gaskets, and failed water pumps, an educated car owner drives further and has a fatter wallet (most of the time).

Don’t let car phobias keep you from maintaining your car. Now for the desensitization therapy.

Go out to the garage. Gently lift the hood and touch the upper radiator hose. See how easy it is?

Want something even easier? Read more helpful articles on caring for your car’s cooling system with additives that work! Irontite has been helping car owners keep their vehicles on the road for more than 60 years. If it didn’t work they wouldn’t still be able to make and sell it. Now sold in most parts stores in North America as well as online at Amazon and the manufacturers’ website.

Car engines are someone complex pieces of machinery, but don’t let that intimidate you when it comes to simple maintenance and care. Check out this article on what causes cars to overheat.

Understanding the Different Antifreeze Types for Your Car

Are you looking for the right engine coolant for your car? Keep on reading this post to know the different antifreeze types and how they’re made.

Are antifreeze and coolant the same thing?

What kind do I need for my engine?

Why is the coolant green? 

If any of these questions have crossed your mind, you’re not alone. The mechanics of your engine are complicated and little things, like antifreeze, make a huge difference in how the vehicle runs. 

This guide breaks down antifreeze types (and their colors) so you know what kind to put in your baby. 

Antifreeze vs Coolant 

Antifreeze is coolant. Coolant is antifreeze. Don’t let the names trick you up. 

Engine coolant is a mix of ethylene glycol and water. Nearly all engines use a 1:1 ratio of coolant: water.

One thing to bear in mind with modern coolants: The jugs you buy at the store are pre-diluted. In the past, coolant was sold as a pure substance that you would have to dilute with water at home before you put it in your car. 

Pre-diluted coolant is more convenient. 

Why Coolant Is Important 

The coolant keeps your radiator from freezing in the winter and overheating in the summer.  It protects the engine and cooling system from corrosion.

Different types of engines require different coolant types. Picking the right one will make your engine run cleaner and more efficiently. The wrong one will be a huge headache later. 

Flushing and sealing your coolant system keeps everything running right. 

Common Antifreeze Types by Color 

Water and antifreeze are both colorless.

Manufacturers started adding colored dye to the mixture in order to differentiate between the coolant and other engine fluids. If your car was leaking a blue fluid, it meant one thing. If it was leaking a pink fluid, it meant another. 

As time went on, and more types of antifreeze were released to the market, manufacturers started added specific colored dyes to specific types of antifreeze so consumers could tell the types and brands apart. 

This guide breaks down the most common types of antifreeze by their commonly associated colors. Not all types of antifreeze are covered. 


If you have a green coolant, you have Inorganic Acid Technology (IAT) coolant. This type of coolant is the original type of coolant on the market. This means that if you drive an older model car, it likely still uses green antifreeze.

This type of coolant is sometimes referred to as conventional low-silicate coolant. This is because it uses silicates as corrosion inhibitors. 

Historically, a green-dyed coolant was designed for cars and small trucks. You would have to dilute the coolant with water and “pre-charge” it with supplemental coolant additives. These additives were designed to protect engine cylinders from corrosion. 

Now, the coolant comes diluted and pre-mixed with all the additives already in it. As long as you change the antifreeze every 24k miles or so, you should be fine. If you choose to push the life of the coolant beyond that, you will want to mix in those additives as specified by the engine manufacturer.


An orange coolant typically indicates that you are looking at Organic Acid Technology (OAT) coolant. This type of coolant uses organic acids as an inhibitor. 

This is the type of coolant usually required for GM, Saab, and VW vehicles.

OAT coolants do not have nitrites added. Contamination with nitrite – such as if you were to add the wrong type of coolant to the system – can drastically reduce the performance life of the OAT coolant. 

Orange-dyed coolants typically protect an engine for 600k miles, as long as they remain pure and uncontaminated. 


A Hybrid OAT (HOAT) coolant is also an option. It is typically dyed yellow. 

This type of coolant mixes technology from the first two to create a low-silicate, nitrite technology. It contains both silicates and organic acids as inhibitors.

Ford, Chrysler, and some other European companies recommend this type of coolant for their cars.

HOAT coolants, like the IAT coolants, require additives mixed back into the coolant system every 25k miles, or as specified by the engine manufacturer.

HOAT coolants formulations are not compatible with OAT coolants because they do contain nitrites. They should not be mixed together.


If you have a red coolant in your cooling system, you have an Extended Life Coolant. This coolant is recommended for use in Toyota, Scion, and Lexus.

It can be used in any engine requiring an OAT engine coolant. 

Red coolant offers 150k miles of protection. Like other OAT coolants, don’t mix it with nitrate or silicate-based antifreeze.

Color Can Lie: Always Read the Label

No one is regulating the color of your coolant. This means that, while it was a good indicator of the type historically, color is not a reliable predictor of what kind of coolant you have kicking around in your garage now.

For example, OAT coolants are usually orange but, depending on who manufactured it, the coolant can look more yellow or red. Some manufacturers have opted for entirely different color schemes for their coolants. Honda has decided to make all of its coolants, regardless of technology, blue. 

You need to carefully read what the bottle says. It’s not safe to rely on the color.  Always double-check your owner’s manual to determine the type of coolant your system needs.  

Other Antifreeze Types By Continent of Origin

Other than color, which is not the best indicator, there is also the country of origin of the car. The country that makes the car is a much more consistent indicator of what type of coolant your car will need. 

Here are a couple of other coolant choices (again, the list is not all-encompassing): 


Europa is generally plagued by a hard water problem. This means that in order to meet European regulations, the coolant would need to be phosphate-free. 

Calcium and magnesium, which are common in hard water, react with phosphate inhibitors to form calcium or magnesium phosphate. These chemical reactions can cause scale formations on engine surfaces.

Europe uses a form of HOAT coolant that is phosphate-free. European HOAT contains a mix of silicates and carboxylates. 

This form of HOAT is recommended for BMW, Volvo, Tesla, Mini, other vehicles. This European coolant disregards a color designation. Instead, Europe requires each manufacturer to create one specific color of coolant.  


Asia has the opposite need of Europe. In Asia, a phosphated HOAT (P-HOAT) is required. 

Problems with poor heat transfers have led to a ban on silicates as corrosion inhibitors in coolants. To protect engines, Asian manufacturers have adopted a mix of carboxylates and phosphates as corrosion inhibitors. 

P-HOAT is used in most Asian vehicles, including Toyota, Nissan, Honda, Hyundai, KIA & others. Typically these coolants are pink or blue.

Your Coolant System Requires Upkeep 

Whatever antifreeze types you use, it will degrade over time as the ethylene glycol breaks down. The breakdown of the coolant occurs more quickly in engines that operate at high temperatures. 

Once a coolant has degraded, the metal of your engine is at risk for corrosion.

If you have an old jug of coolant sitting around the garage and you aren’t sure if it’s good anymore, use a refractometer to measure the glycol: water ratio. This ratio will tell you the level of freeze protection and the concentration of corrosion inhibitors. 

When in doubt, buy new coolant. Using a high-quality coolant and performing basic maintenance will protect your engine for the long haul.  

Check us out here to learn more about Irontite products and see how they can protect your engine alongside regular maintenance. 

Related Articles:

 What Is Antifreeze and What Is It Used For?