How To Flush Engine Coolant System And Heater Core

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Keep Your Engine Cool And Heater Working

We will be going over how to flush your radiator, engine, and heater core! It is critical to flush your cooling system and put fresh antifreeze in it so that your block won’t crack in the winter, and prevent rust from forming. You can clearly see in our Jeep cooling system that we were flushing, why is bad. Additionally, we cover how to back flush the engine and heater core without removing the thermostat 

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How To Flush And Clean Coolant System Plus Heater Core - Chris Does What

Choose Your Antifreeze:

The first step is to drain the cooling system of your vehicle. Antifreeze shouldn’t be poured down a drain or dumped on the ground because it contains chemicals. Some types are sweet and can harm animals. It won’t hurt to dump out water, which is a big reason to flush your cooling system. Whenever you are unsure what type of fluid is in your vehicle, capture and recycle it.

Remove The Lower Hose On The Radiator - Chris Does What

Remove The Lower Hose On The Radiator

Having removed the fluid from the cooling system, you will need to disconnect the bottom hose from the radiator. When removing the hose, be sure you are not under it as there will still be fluids left in the cooling system. The hose will remain disconnected during the cooling system flush.

Remove Heater Core Hose - Chris Does What

Remove Heater Core Hose

Take the radiator and heater core hose closest to the thermostat housing after disconnecting the bottom hose. If you are unsure of which heater hose is closest to the thermostat, look for the hose closest to the top radiator hose. With the heater core hose, we can flush the system without removing the thermostat, which requires a new gasket. 

Remove Top Radiator Hose - Chris Does What

Flushing The Engine And Heater Core

Having disconnected the coolant system hoses, we can now use the water hose to flush the engine. Video shows this the best, but it’s simply getting water through the heater core and engine. Ensure water flows through the heater core hose and the plug where it connects. By looking at the bottom radiator hose, you will be able to tell if water is getting through the cooling system.

Flushing The Engine And Heater Core - Chris Does What

Flushing The Engine - Chris Does What

You also want to rinse out the top radiator hose once you see clear water flowing out of the bottom radiator hose through the heater core and engine. The top radiator hose needs to be disconnected from the thermostat housing. Once it is off, you can run water through the hose and top of the thermostat house. This water won’t run through the engine if you have a thermostat in the thermostat housing

Flush top Radiator Hose And Thermostat - Chris Does What

If you don’t have a thermostat, you need to install one. The absence of a thermostat will not only prevent the engine from reaching operating temperature. In the winter, the heater will remain colder for much longer. If you don’t live in Florida, you probably want heat as quickly as possible.

Flush The Radiator Real Good

Don’t forget to flush your radiator! While the order in which you flush things isn’t all that important, we just saved the radiator for last. Not flushing a part of the system will leave that nasty stuff in the cooling system. That kinda seems like a waste of time skipping a step.

Flush The Radiator Real Good - Chris Does What

Flushing our radiator was similar to washing your hair instructions, rinse and repeat. We used a shirt to plug the bottom of the radiator. Don’t use the bottom radiator hose, it will just put nasty water back into your engine. You simply fill the radiator up with water until it comes out the top and then let it drain out the bottom. We did this until the water draining out the bottom looked clear.

How To Avoid Vapor Lock With Engine Flush

Now we have to put it back together. Prior to filling the cooling system, the cooling hoses, other than the heater hose, must be reinstalled. When adding coolant you want to make sure that fluid comes up to where the heater core plugs in. Putting the system together and filling could vapor lock your water pump and prevent the engine from cooling. I have done this before, wasn’t fun.

How To Avoid Vapor Lock With Engine Flush Process - Chris Does What

After the engine has been filled to the heater core thermostat plug, replace the hose and continue filling. We used a 50/50 mix, so we did not add any water back to the system. If you are mixing antifreeze, you should look at the cooling system capacity and add half antifreeze and the other half to the water.

Did You Flush The Vehicle Cooling System Right

It’s time to start the engine now that you have coolant in it. So we could see the coolant when it circulated in the engine, we left the cap off the radiator. Turn on your heater, if the warm air doesn’t come from the heater like it did before, you may have air in the system. Shut off the vehicle and let it cool, then unplug the top heater core hose at the fire wall to get the air out.

Did You Flush The Vehicle Cooling System Right -Chris Does What

After you are sure everything is working correctly, top off the system, put the cap on, and run the engine for five or ten minutes at normal temperature. This will allow the cooling system to pressurize making it easy to see coolant leaks. If you have a coolant leak, fix it. If there are not coolant leaks and the engine is staying at a normal temperature, your done.

We hope this helps you clean your cooling system on your ride. If you want to see more of the content we create, subscribe.

Jump To Video Topics:

  • 00:00 How To Flush And Clean Coolant System Plus Heater Core Intro
  • 01:47 Drain And Take Prepare Vehicle Cooling System To Be Flushed
  • 02:35 Flush Vehicle Cooling System With Water Hose
  • 06:10 Putting Cooling System For Vehicle Back Together
  • 06:49 How Not To Vaper Lock Your Cooling System While Flushing Your Engine.
  • 07:48 After Engine Flush Steps For Success
  • 09:37 Tips And Final Thoughts On How To Flush Engine Cooling System

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