How to Flush Your Cooling System | YourMechanic Advice (2024)

Flushing the cooling system is part of every vehicle's scheduled maintenance. This procedure is usually required every two to four years, depending on the vehicle.

It is important to perform this maintenance at its scheduled time because the radiator plays a big role in keeping your car’s engine cool. Failure to keep the engine cool could lead to engine overheating and costly repairs.

Flushing your radiator and cooling system is a straightforward procedure that you can do at home with a little patience and some basic knowhow.

It must be noted, however, that if your vehicle is leaking coolant or if you find that the engine is overheating, then a radiator flush is not recommended. The cooling system cannot be flushed if it is not functioning properly in the first place.

Part 1 of 1: Flush the cooling system

Materials Needed

  • Cat litter
  • Distilled water, about 3-5 gallons
  • Drain pan
  • Five gallon buckets with lids
  • Floor jack
  • Latex gloves
  • Pair of pliers
  • Pre-mixed coolant specific to your vehicle, about 1-2 gallons
  • Rags
  • Safety glasses
  • Safety jack stands x2
  • Screw driver
  • Socket and ratchet

  • Note: Always start with a cold vehicle when flushing a cooling system. This means the vehicle has not been used for some time to allow everything in the engine to cool down.

  • Warning: Do not open the cooling system on a hot vehicle, or serious injury can occur. Let the vehicle sit for at least two hours so it is cool enough to work on safely.

How to Flush Your Cooling System | YourMechanic Advice (1)

Step 1: Locate the radiator. Open the hood of the car and locate the radiator in the engine bay.

How to Flush Your Cooling System | YourMechanic Advice (2)

Step 2: Access the drain spout. Locate the bottom of the radiator, where you will find the drain spout or petco*ck.

It may be necessary to remove any splash shields to gain access to the bottom of the radiator and the petco*ck. You can use a tool, such as a screw driver, to do this.

How to Flush Your Cooling System | YourMechanic Advice (3)

  • Tip: It may also be necessary to raise the front of the vehicle to have enough room to access the spout or petco*ck on the radiator from underneath the vehicle. Use the jack to lift the vehicle and use jack stands to secure it for easy access.

Please refer to your vehicle owner's manual on how to properly and safely lift the car.

How to Flush Your Cooling System | YourMechanic Advice (4)

Step 3: Loosen the drain spout. Place a drain pan or bucket below the vehicle before opening the drain spout or petco*ck.

If you are unable to loosen this piece by hand, then use a pair of pliers to assist you with the removal.

Once this is done, proceed to remove the radiator cap as well. This will allow the coolant to drain out quicker into the drain pan.

How to Flush Your Cooling System | YourMechanic Advice (5)

Step 4: Drain out the coolant. Allow all of the coolant to drain into the drain pan or bucket.

  • Tip: Take care to not let the coolant drip on to the ground, as it is toxic to the environment. If you do spill coolant, put some cat litter on to the spill. The cat litter will absorb the coolant and can later be swept up with a dustpan and bagged for proper, safe disposal.

How to Flush Your Cooling System | YourMechanic Advice (6)

Step 5: Fill distilled water. Once all the coolant is drained, close the petco*ck and fill the cooling system with plain, distilled water.

Replace the radiator cap, start the engine, and run the vehicle for about 5 minutes.

How to Flush Your Cooling System | YourMechanic Advice (7)

Step 6: Check the system pressure. Shut off the car. Squeeze the upper radiator hose to determine if the system has pressurized.

  • Warning: Do not open the cap if the radiator hose is pressurized and firm. When in doubt, wait 15-20 minutes between running the vehicle and opening the cap.

Step 7: Drain out the distilled water. Open the petco*ck again, then the radiator cap and allow the water to drain out of the cooling system into the drain pan.

Repeat this process 2 to 3 times to remove the old coolant from the cooling system.

Step 8: Dispose the old coolant. Pour the used coolant and drain water from the drain pain into a five gallon bucket with a secure lid and take it to a recycling center for safe disposal.

How to Flush Your Cooling System | YourMechanic Advice (8)

Step 9: Fill the coolant. Grab the coolant specified for your vehicle and fill the cooling system. Leave the radiator cap off and start your vehicle.

How to Flush Your Cooling System | YourMechanic Advice (9)

  • Tip: The type of coolant will vary from one manufacturer to another. An older vehicle may use the typical green coolant, but newer vehicles have coolants formulated specifically for their engine’s design.

  • Warning: Ensure that you never mix the different types of coolant. Mixing coolant can cause damage to the seals inside the cooling system.

Step 10 : Circulate fresh coolant in the system. Return to the inside of your car and set your heater to High to allow the fresh coolant to circulate throughout the entire cooling system.

You can also idle your vehicle at 1500 rpms for several minutes by pressing on your gas pedal while in park or neutral gear. Doing this allows the vehicle to reach the usual operating temperature more quickly.

Step 11: Bleed air out of the system. As the vehicle warms up, air will bleed out of the cooling system and out of the radiator cap.

Monitor the temperature gauge on your dashboard to ensure that the vehicle does not overheat. If the temperature begins to rise, shut the vehicle off and let it cool down; it’s likely that an air pocket is trying to find its way out. After it cools down, start the vehicle again and continue to let the air bleed out of the cooling system.

When all of the air is out, the heater will blow strong and hot. When you touch the lower and upper radiator hoses, they will have a similar temperature. The cooling fan will come on indicating that the thermostat has opened and the vehicle has reached operating temperature.

Step 12: Top off the coolant. When you are confident that all the air is out of the system, top off the coolant in the radiator and secure the radiator cap.

Re-install any splash shields, lower the car from the jack stands, clean up all of your materials and perform a test drive. Performing the test drive will help you verify that the car is not overheating.

  • Tip: On the following morning, check the coolant level in the radiator before starting the vehicle. Sometimes there may still be air left in the system and it will find its way to the top of the radiator overnight. Simply top off the coolant, if needed, and you are good to go.

Car manufacturers recommend that you flush the radiator at least every other year or every 40,000 to 60,000 miles. Ensure that you flush your car’s radiator at the recommended intervals to prevent it from overheating and to help maintain an efficient radiator system.

Overheating can cause serious, expensive damage like a blown head gasket (which typically requires complete engine replacement) or warped cylinders. If you suspect that your engine is overheating, get your car inspected by a certified mechanic, such as one from YourMechanic.

Flushing the radiator correctly helps to clean and prevent dirt and sediment buildup. By performing this routine maintenance procedure, you can help your car’s radiator in perfect working condition.

The statements expressed above are only for informational purposes and should be independently verified. Please see ourterms of servicefor more details

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Flushing the Cooling System

Flushing the cooling system is a crucial part of a vehicle's scheduled maintenance. It is typically recommended to be done every two to four years, depending on the specific vehicle. The radiator plays a significant role in keeping the car's engine cool, and failure to maintain it properly can lead to engine overheating and costly repairs.

Performing a radiator flush is a straightforward procedure that can be done at home with some basic knowledge and patience. However, it's important to note that if a vehicle is leaking coolant or experiencing engine overheating, a radiator flush is not recommended. Additionally, the cooling system cannot be flushed if it is not functioning properly in the first place.

The process of flushing the cooling system involves several steps, including locating the radiator, accessing the drain spout, draining the coolant, filling with distilled water, checking system pressure, disposing of the old coolant, filling with new coolant, circulating fresh coolant, bleeding air out of the system, and topping off the coolant.

It's essential to use the specific pre-mixed coolant recommended for the vehicle, as different manufacturers may have different formulations. Mixing coolant types can cause damage to the seals inside the cooling system. Additionally, after flushing the radiator, it's recommended to perform a test drive to verify that the car is not overheating.

Regularly flushing the radiator helps prevent overheating and maintains the efficiency of the radiator system. It also helps clean and prevent dirt and sediment buildup, contributing to the overall health of the vehicle.

It's important to follow the manufacturer's recommendations regarding the frequency of radiator flushing to prevent potential damage, such as a blown head gasket or warped cylinders, which can result from overheating.

If there are concerns about engine overheating, it's advisable to have the car inspected by a certified mechanic to address any potential issues.

Remember, the information provided here is for informational purposes and should be independently verified. Always refer to the vehicle's owner's manual for specific maintenance guidelines.

How to Flush Your Cooling System | YourMechanic Advice (2024)

FAQs

What is the best way to flush a cooling system? ›

How to Flush Your Radiator / Cooling System
  1. Safety First. ...
  2. Setting Up The Job. ...
  3. Press Down and Remove the Radiator Cap. ...
  4. Locate the Drain Plug and Loosen. ...
  5. Fill the Cooling System with Distilled Water. ...
  6. Install the Radiator Cap and Run the Engine. ...
  7. Loosen Lower Radiator Hose. ...
  8. Drain Out Final Dirty Water.

How do you clear a blockage in a cooling system? ›

Drain the coolant from your radiator by opening the drain valve on the bottom of your radiator. Next, drain the coolant from your engine block by opening the block drain also. Add the purchased radiator flush to the radiator and let the car run. Drain like the old coolant, and suddenly your car is clean and fresh.

Do you need to remove thermostat to flush coolant? ›

No, it is not necessary to remove the thermostat. In fact, some cars you don't want to remove the thermostat while running the vehicle. The reason for this is that the thermostat can be used to direct coolant flow. If it is out, parts of the engine may not be getting coolant as designed.

What is the recommended time for a coolant flush? ›

HOW OFTEN SHOULD YOU FLUSH THE COOLANT? Depending on the vehicle and the coolant, the average time between flushes is two years or 30,000 miles for silicated coolants and up to five years or 100,000 miles for an extended drain coolant. You can tell which type of coolant you have by the color.

Can you flush cooling system yourself? ›

The good news is that you can keep your engine cool by conducting a coolant flush on your own. Even if you're not super knowledgeable about cars, it's easy enough to replace your old coolant with a fresh supply.

Does cooling system flush work? ›

A coolant flush can prevent damage to both your vehicle's cooling system and engine. Keeping your system clear of unwanted debris can protect components of your cooling system, such as hoses and coolant lines. These elements of your engine's cooling system can prevent significant damage to your vehicle.

Will a radiator flush unclog a radiator? ›

Because radiator flushes help to remove any dirt and debris from the engine, it allows the entire system to perform better.

How do you know if your cooling system is clogged? ›

To test for a clogged radiator, one can drain the radiator and observe the flow of the coolant, which should be consistent. If the coolant is flowing slowly or inconsistently, the radiator is likely clogged. Rust in the cooling system can also cause clogging of the radiator and heater core.

Why is my car overheating after a coolant flush? ›

It's still air in the system or wasn't bleed properly also possibly not enough coolant or a bad radiator cap be sure to let the car idle while topping off the coolant until it pushes all the air bubbles out before putting the radiator cap back on doing this to soon will trap air and cause overheating.

Do you need to flush coolant or just top off? ›

In many cases, it's enough to simply top up the coolant reservoir in your engine, but sometimes, your vehicle may need a coolant flush. During this procedure, a mechanic will completely empty the old coolant from your car. They will then top your reservoir up and make sure that your car hasn't suffered any damage.

Will coolant flush stop overheating? ›

Prolonging the lifespan of your engine: A radiator flush removes contaminants that cause rust and corrosion, preventing the build-up of deposits that can damage the engine. Preventing overheating: As mentioned earlier, a radiator flush can prevent overheating, which can cause severe and costly engine damage.

Will a bad thermostat drain coolant? ›

No, a bad thermostat cannot directly cause coolant to leak. The thermostat is responsible for regulating the engine's operating temperature by controlling the flow of coolant through the engine. If the thermostat fails, it can cause the engine to overheat or run too cold, but it will not cause coolant to leak.

How many gallons of coolant do I need for a flush? ›

Most vehicles need 1–1.5 gallons of pure coolant after flushing, check owner manual if need be.. I only use a flush for extremely corroded systems. I drain, fill with water and drive it, letting the water system flush the system for up to 1 week with a weak coolant solution. Than drain and fill as normal.

How many gallons of water does it take to flush a coolant system? ›

Repeat filling the radiator with 1 gallon (3.8 L) of distilled water, running the car with the heat on, and draining it once it's cooled. This ensures that any leftover debris or cleaner is flushed out of the system, and that your radiator is ready for fresh coolant.

What is the difference between a coolant exchange and a flush? ›

When it's time for a coolant exchange, it's not just about adding new coolant. The old coolant is likely dirty, and simply topping it up would compound the issue. The fluid flush process involves draining the entire cooling system and replacing it with fresh coolant.

What is the difference between a coolant flush and a radiator flush? ›

A coolant flush is another name for radiator flush, a procedure to clean your vehicle's cooling system of sediment and rust. The coolant keeps your engine from overheating while running, and from freezing in cold weather when it's not running.

Can you leave radiator flush in overnight? ›

1 Answer. Everything I'm reading about doing an engine flush states it should not be left in longer than six hours. If you go past that point, do so only at low engine power.

How do you flush a radiator without removing it? ›

You will want to place your hose or water source onto the inlet valve of your radiator, turning on the water supply to the hose and flushing the radiator out. Continue to run water through the radiator until all the water exiting the radiator is clear and free from sludge or debris.

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