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.

Radiator Flush Comparison Guide: How to Choose a Radiator Flush

Read this beginners guide to learn how to choose the best radiator flush for your car. Find out which product is the best for your car. Read more here.

If you take your car for granted, it’ll most likely overheat.

When your car’s engine overheats, everything can and will go wrong. Do you know what stands between a functioning vehicle and complete engine failure? —the knowledge and execution of proper car maintenance.

Understanding how to maintain your car is essential to its functionality and lifespan. One of the most overlooked things by car owners is the cooling system. If you neglect your car’s cooling system, it will create a domino effect of failing parts. Primarily your engine.

A radiator flush is essential to avoid extensive and costly repairs in the future. You don’t have to be a mechanic to maintain your vehicle, you just have to keep reading!

Wondering About a Radiator Flush?

If you’re wondering whether you have to flush your radiator from time to time, the answer is yes. 

There are different kinds of flushing methods and different “cleaning” products to use while flushing. In any method, however, the principle is the same. To circulate “flush” debris and corrosion build up out of the engine and radiator.

A good radiator flush process involves adding a specific cleaner to your car’s cooling system. It helps to get rid of any rust or sediment that has built up over time. It is completely flushed through the entire cooling system along with the rest of the debris. Once everything is out, a new coolant mixture is added and possibly along with a conditioner for added protection from future leaking.

If you’re wondering whether you can get away with just a simple coolant change, the answer is no. Even with the best coolant mixture, the cooling system will still become dirty over time making it very important to flush the system before adding fresh new coolant.

Coolant is typically a 50/50 mix of water and antifreeze. Antifreeze is made up of ethylene glycol, lubricants, and corrosion inhibitors in general. It works to absorb the heat from your car’s engine. Once the heat is absorbed, it releases it through the radiator. Its purpose is to prevent your engine from overheating and to not turn to ice in cold weather.

The chemicals in antifreeze deteriorate over time. This weakens the protection of your engine from corrosion and overheating. It gets worse if you have dissolved solids or chlorine from the water in your cooling system as well. This is how you get sludge built up in your engine.

Once rust and sludge build up in your cooling system, it can cause serious and costly damage to your engine. This is why a coolant flush is recommended every 30,000 miles or five years—whichever comes first. (Always check with your car’s owner’s manual to be sure).

How Does a Coolant Flush Work?

A coolant flush done by a trustworthy mechanic will run you about $150, give or take. The entire process, however, is not too difficult to do on your own.

Either you or your mechanic will drain your radiator and engine block from all the old coolant. When the last of the old coolant is drained, a chemical cooling system cleaner is added to the cooling system along with water to fill it. 

Your car should for about 10-20 minutes to warm up. It must reach its optimal performance temperature to ensure that the cleaner cycles through the system. When it reaches the right temperature, the chemical cleaner and water are circulating under pressure to force loose all the gunk that may have collected in your hoses, engine, and radiator.

you then wait for the engine to cool before draining. After flushing, you will need to rinse at least two times or more. Refill with water and run the engine back up to temperature for 10 minutes or so and then let it cool again and drain. This is necessary because draining only removes about 50% to 60% of the solution from a typical cooling system So repeating the rinse helps to get all the loosened debris and remaining flush chemicals completely out.

Once all of the old coolant, dirt, rust, sludge, and other deposits have been cleaned out, the new coolant mixture can be added.

Pro Tip: When it comes to coolant, it’s best to buy the concentrated kind and dilute it yourself using distilled water! You can use an inexpensive tool from your local parts store called a hygrometer to check the quality of your mixture. Remember that a good portion of your rinse water remains in the engine after draining so you may need to adjust your 50/50 mix slightly to account for that.

How to Choose a Radiator Flush

The fluids that you use in your car are important factors in its performance and lifespan. Whether it be the grade of gasoline, type of engine oil, transmission fluid or coolant mixture, you want to use quality products. The same goes for the type of chemical cleaner and conditioner you choose to use for your radiator flush. 

You only have to do a radiator flush every so often, so you want to make each one count. There are many cleaners out there on the market. But, which type of cleaner to use is not a simple choice. They all say about the same thing on the bottle, that they are the best choice for cleaning your radiator or cooling system. But there is one that stands out.

Irontite Thoro-Flush coolant cleaner is arguably the most powerful cleaner on the market today. This industrial level brand is capable of cleaning clogged heater cores and cooling systems. It will even clean residue from your fuel tank—which is not something that most coolant cleaners can do and should only be done with the fuel tank removed.

In addition to the Thoro-Flush, Irontite also offers All Weather Seal and Ceramic Motor Seal. These are great to use post-radiator flush for maximum protection. Depending on what your concerns are, you only need to use All Weather Seal. It is an excellent choice for preventative leak protection.

If your concerns are porosity, cracks, or a head gasket leak, then Ceramic Motor Seal is the way to go. It will create a thin coat in your cooling system, filling in any porous surfaces and provide protection from oxidation. A smoother surface will provide for better coolant flow, allowing a better overall engine performance.

If your concerns are the head or intake gasket leaks, leaky seals, a leaky radiator, or future leaks, then the All Weather Sealis recommended. You can pour it right into your coolant mixture. It will remain dissolved and suspended within the coolant mixture to safeguard your engine’s cooling system from leaks continuously.

Of course, you can use all three products or just two of them, but it’s always a good idea to start with a flush of the radiator and cooling system first using Thoro-Flush!

Now You Put the Cool in Coolant

Now you know the importance of your coolant system and what type of cleaner and conditioner to use for your next scheduled radiator flush.  And you might even take on the task yourself and save a nice chunk of change.

For more information on Irontite, our products, and anything else you’d like to learn about proper car maintenance, come and check us out!