Maintaining a properly functioning cooling system is vital to prevent engine overheating and ensure the longevity of your vehicle. Among the various maintenance tasks involved, a coolant flush is a crucial procedure often overlooked. But can a coolant flush prevent overheating, or is it just another routine maintenance ritual?
In this article, we will cover what a coolant flush does, its importance, and it’s role in preventing a car from overheating.
What Does a Coolant Flush Do?
A coolant flush is a simple maintenance procedure that involves draining the coolant, flushing the system by hand or with specialist equipment, and refilling the system. There are many reasons for performing a coolant flush; they include:
- Contaminant Removal – Coolant can become contaminated with debris, rust, scale, or other particles that hinder its effectiveness. The coolant passes through many different components constructed of different materials. Flushing the coolant removes these contaminants.
- Corrosion Prevention – Coolant contains additives that help prevent corrosion and rust in the engine, radiator, pipework, etc. Over time, these additives become weaker. Flushing the coolant allows for fresh coolant with proper corrosion inhibitors to be added.
- Overheating Prevention – Cooling systems use the proper coolant flow to regulate engine temperatures. If the coolant becomes old, degraded or is the incorrect dilution with water, it may not effectively transfer heat, leading to potential engine overheating issues.
Will a Coolant Flush Help Overheating?
Apart from the odd few occasions where there is an issue with the coolant, or its ability to circulate, a coolant flush will not help solve an overheating problem. Coolant is rarely the cause of overheating if it is in good condition and at the correct strength.
The strength of coolant and its properties will ‘wear out’ over long periods, which is why coolant flush is recommended every few years. However, coolant, even if left for very long periods in a car, will still contain properties that will help it do its job; they just get weaker. Remember, the coolant’s job is to absorb heat from the engine; the heat is exchanged in the radiator and cooled to be pumped back around.
The coolant will always do this job if there is coolant in the engine and it is circulating. So if the car is overheating, a coolant flush will not solve the problem because there will probably be another cause of the overheating.
What Can Cause an Engine to Overheat?
An engine that overheats is usually caused by other problems such as:
- Insufficient coolant or coolant leak
- Thermostat failure
- Water pump malfunction
- Radiator blockage
- Cooling fan failure
- Defective radiator cap
- Faulty coolant temperature sensor
- Low engine oil
- Clogged or damaged hoses
- Faulty belt or tensioner
- Malfunctioning ECU
- Excessive load or towing capacity
- Running the engine at high RPM for extended periods
- Ignition timing issues
- Air/fuel mixture imbalance
- Intake air restriction
- Exhaust system restriction
- Damaged or worn-out piston rings
- Cylinder head gasket failure
- Engine coolant system contamination.
The list goes on, and although the coolant contributes to keeping the engine temperatures down, if the coolant mixture is correct and there is nothing to restrict the coolant flow, replacing the coolant will not solve an overheating problem.
Reasons Why a Coolant Flush Might Help Overheating
There are a few instances where flushing the coolant will stop an overheating problem. However, these rarely occur if a car is properly maintained and serviced regularly.
Blocked radiator or pipes
If the coolant has not been replaced for long periods, a blockage may prevent the coolant from circulating, which will cause overheating. Depending on the location of the blockage, you may even experience issues such as the radiator hose popping off. This is one of the couple occasions when a coolant flush may help with overheating. The blockage could be caused by a build-up of grime, rust, scale, and all sorts of contaminates; especially as the coolant has been left, its properties that prevent this from happening will be almost none existent.
When the coolant flush is performed and the system is empty, it must be flushed out by a machine that will send pressurized water or a solution that should clear the blockage. Once the backup is removed, it may need to be refilled and drained a few times to remove all the contaminants from the system. When it is filled with coolant, it should circulate, correctly cooling the vehicle.
Incorrect strength coolant mixture
An incorrect coolant strength mixture can cause overheating due to its impact on the coolant’s ability to regulate temperature effectively. Coolant, or antifreeze, is typically a mixture of water and ethylene glycol or propylene glycol. The ratio of coolant to water is crucial for the longevity of an engine.
When the coolant mixture is too weak or diluted, meaning there is a higher proportion of water to coolant, it can cause several issues such as:
- Reduced Boiling Point – Coolant raises the mixture’s boiling point, allowing it to withstand higher temperatures without vaporizing. If the coolant concentration is too low, the boiling point decreases, making the combination prone to boiling and evaporating at average operating temperatures. This can lead to the formation of steam bubbles and an airlock that will disrupt the coolant flow, causing the engine to overheat.
- Reduced Heat Transfer Efficiency– Coolant works with water to efficiently transfer heat away from the engine. When the coolant mixture is too weak, its ability to absorb and dissipate heat diminishes. This can result in reduced cooling performance and inadequate heat transfer, leading to engine overheating.
Another thing to note is that the coolant contains anti-freezing agents to prevent the coolant mixture from freezing in colder climates. If the coolant freezes and you try to start the engine, the coolant will not circulate, which can cause engine damage.
Testing the strength of coolant is very simple; the best way is to use coolant test strips which you dip in the coolant and check the strip’s color against a chart that will tell you its boiling point. A coolant flush will most likely fix the overheating issue if the coolant strength is too low.
Low coolant level
A low coolant level doesn’t usually happen for no reason. The coolant system is sealed, and the coolant doesn’t get combusted unless the head gasket has failed. So if the coolant level is low or the coolant is empty, there may be a cause for the leak. But if it is just down to never being topped up or when it is topped up, just water is used without adding any extra coolant; then a coolant flush will help solve the overheating.
Without the proper amount of coolant, air can be drawn into the system, where you can get airlocks that will stop the coolant from circulating, which causes overheating. Flushing the coolant can remove the trapped air by bleeding the coolant system after it is refilled.
If the coolant level is low and the car is overheating, just filling the coolant back up to the correct with water, bleeding the system, should confirm if the low coolant level was the cause of the overheating. Then because the coolant is at the incorrect strength, you should thoroughly flush the system, and refill will correct the coolant mixture.
How Do You to Tell the Coolant Needs Flushing?
- Discolored Coolant – If you check in the coolant reservoir and notice that it has become dark, murky, or rusty in color, it is a sign that the coolant needs to be flushed. Discoloration indicates the presence of contaminants or degradation of the coolant additives.
- Sediment or Particles – Inspecting the coolant and finding visible sediment, debris, or floating particles suggests that the cooling system has accumulated contaminants. There is a high risk of blockages starting to appear, so flushing the coolant should be done asap.
- Testing the coolant – There are a couple of different ways to test the coolant: one with coolant test strips and the other with a coolant test tool that looks like a turkey baster with colored balls inside. Both require a sample of the coolant taken from the reservoir and testing the strength of its boiling point.
How Often Should You Flush the Coolant?
The recommended time frame for coolant flushes alters from one vehicle brand to another. However, a general guideline is to perform a coolant flush and replacement every 2 to 5 years or every 30,000 to 50,000 miles (48,000 to 80,000 kilometers), whichever comes first. It’s essential to refer to the vehicle manufacturer’s recommendations and consult the owner’s manual for the exact guidelines.
Additionally, some coolant manufacturers offer extended-life or long-life coolants that claim to last longer, typically 5+ years or 100,000 miles (160,000 kilometers). If your vehicle is filled with such a coolant, you should follow the recommended intervals provided by the manufacturer of that coolant. But remember to inspect and test the coolant more frequently if ignoring the vehicle manufacturers’ guidelines.
Keep in mind that certain driving conditions, such as frequent towing or driving in extreme temperatures, and you should consider performing a coolant flush more often.
Final Points
A coolant flush is essential to prolonging an engine’s life and cooling system. While flushing the coolant can prevent the car from overheating, it is rarely the cause unless it has been wholly neglected outside the vehicle’s recommended replacement guidelines.
