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What is a Car Coolant and How Does it Work?

Team AckodriveMar 12, 2024

Driving during summer usually means blasting the A/C to stay comfortable in sweltering temperatures. But while you may be enjoying cool air inside the cabin, the heat taking a toll on your engine could cause permanent damage if left unchecked. Proper engine temperature maintenance is vital for optimum performance and longevity.

The magic fluid responsible for this difficult balancing act is coolant. This guide will explore everything you need to know about this often overlooked liquid running through your engine, how to monitor it, and steps to keep your car's cooling system running in tip-top shape when temperatures rise.

Let's get started.

What is the Purpose of a Coolant in a Vehicle

The cooling system in your car has one primary purpose - to keep the engine running at optimum temperature. The coolant, also known as antifreeze, circulates through passages in the engine block and cylinder head, absorbing excess heat generated by combustion. Without a properly functioning cooling system regulating operating temperature, your engine would quickly overheat, reducing performance, efficiency, and even complete breakdown over time.

The water-based coolant mixture flows from the engine to the radiator, which cools before circulating back to absorb more heat. This cooling effect allows the engine to run smoothly even in scorching summer weather. In frigid winter temperatures, antifreeze in the fluid mix prevents it from freezing over and damaging engine components. By maintaining optimum operating temperature year-round, coolant is vital for protecting your investment and allowing proper engine operation.

How Does the Coolant Work Within the Engine Cooling System?

Inside your engine, hundreds of controlled explosions are happening every minute. This combustion process converts fuel into power that moves your vehicle while generating enormous leftover heat. Without an effective method of dispersing this waste heat, engine components would rapidly deteriorate.

This is where the cooling system comes in - its main components include the radiator, water pump, thermostat, hoses, and passageways bored into the engine block and cylinder head. 50/50 coolant, comprised of half water and half antifreeze, flows through these passages, absorbing heat from hot engine parts. The water pump then circulates the hot coolant from the engine to the radiator.

As it passes through the radiator’s thin tubes, the coolant dumps waste engine heat into the outside air stream from forward movement or electric fans. Once cooled, the fluid flows back to absorb more heat from the engine. The thermostat controls the flow rate to maintain optimum operating temperature as driving conditions change. This beautifully efficient closed-loop system is vital for dispersing damaging waste heat and keeping engine temperatures in the safe zone.

The Different Types of Car Coolant

You’ll have a few options on the auto parts store shelf when considering an antifreeze or coolant fluid change. Modern coolant technology falls into three main categories, each with its own formulation and benefits:

1. Inorganic Additive Technology (IAT)

IAT coolants, distinguished by their bright green fluorescent colour, have been around for decades. They contain silicates as corrosion inhibitors and phosphates, which protect against scale and rust formation within the cooling system. However, phosphates have been eliminated from most antifreeze formulas today. While still available, IAT fluid is being phased out due to newer technologies, superior heat transfer abilities and improved corrosion protection.

2. Organic Acid Technology (OAT)

OAT antifreeze contains organic acids as their main corrosion fighters, carboxylates, and other organic salts. GM’s Dex-cool orange fluid is the most common example, but many manufacturers have their own variations. OAT is typically phosphate and silicate-free. It offers excellent corrosion protection and heat transfer properties while preventing scale buildup. With its long service life, OAT fluid is great for modern aluminium engine designs. However, it costs more than conventional antifreeze.

3. Hybrid Organic Acid Technology (HOAT)

The goal of HOAT fluids is to combine the strengths of traditional IAT and OAT technology while minimising their drawbacks. HOAT contains organic acid inhibitors of OAT but leaves out the silicates found in conventional IAT coolants. The result is well-rounded protection against corrosion and scale in one formula. HOAT antifreeze is available in varying colours depending on the brand. They offer solid versatility for use in most vehicle makes and models. Depending on included additives, HOAT formulas can come in these variations:

4. Phosphate-free HOAT or Hybrid OAT

As their names suggest, these HOAT formulations contain NO phosphates. They prevent scale and corrosion through purely organic inhibitors. Compatible with any antifreeze type, they offer maximum heat transfer without silicates potentially causing buildup.

5. Phosphated HOAT

Phosphate HOAT adds limited phosphates to the fluid to aid corrosion protection, striking a balance between newer organic and older inorganic additives.

6. Silicated HOAT (Si-HOAT)

Si-HOAT contains silicate additives to boost anti-corrosion abilities, making them more compatible with older cooling systems designed for traditional silicated green antifreeze.

As newer vehicles shift toward aluminium and other metal alloys under the hood, OAT and the latest phosphate-free HOAT blends provide advanced protection. But for older cars, Si-HOAT remains a sound choice.

Also read: Synthetic oil vs normal oil for cars

Characteristics of a Good Car Coolant

Antifreeze and coolant blends don’t contain just one ingredient. Various components mixed together achieve the fluid’s primary jobs - cooling, anti-freeze, anti-corrosion and scale prevention. Here’s a closer look at key ingredients you’ll find in that brightly coloured fluid:

1. Water: The main component, water, has excellent heat-absorbing properties due to its high specific heat capacity. It comprises approximately half of the finished 50/50 coolant mix flowing through your engine. Deionised or distilled water is preferred for mixing to avoid mineral deposits and maximise heat transfer.

2. Ethylene Glycol: This alcohol-based compound makes up around 95% of antifreeze concentrates before mixing with water. Ethylene glycol helps coolant maintain a much lower freezing point than water alone, down to -34°F, depending on the ratio. It also raises the fluid’s boiling point to 265°F at a 50/50 mix. This increased cooling range suits different climates and driving loads.

3. Propylene Glycol: Far less toxic than ethylene glycol, you’ll find this alcohol replacing its cousin in certain antifreeze formulations. It performs similar cooling functions, albeit at not quite as extreme temperature limits. GM’s Dex-Cool is one brand containing propylene glycol instead.

4. Corrosion Inhibitors: These vital additives make antifreeze effective at limiting corrosive damage inside the cooling system. Inorganic inhibitors include phosphates and silicates, while newer organic options contain one or more organic acids for well-rounded protection. Finding a coolant formula to match your vehicle’s metal components is key to longevity.

Alongside these main substances, varying dye colours, clarifying agents and speciality additives all play minor roles in robust antifreeze and coolant mixes.

How to Choose the Right Car Coolant

With various coolant technology options available, picking the optimal fluid for your vehicle can get confusing when adding a fresh charge or flushing the system. Here are helpful tips for choosing antifreeze and coolant:

Consult your owner’s manual for the manufacturer’s specific recommendation. Most spell out a preferred formula.
Stick with the factory fill coolant type, if possible, shown on the original reservoir cap or info sticker under the hood.
If unclear on what’s circulating, have a shop test the alloy and chemical makeup. Then, refill with a matching, compatible formula.
For newer aluminium vehicles, always avoid silicate-based fluids. Stick with OAT and the latest phosphate-free HOAT options specifically for aluminium engines. In older iron blocks, IAT and Si-HOAT antifreeze remain valid choices.

The right chemistry maximises system durability - conflicting additives can actually increase corrosion. So consult guides or dealership service advisors if you need help determining whether a fluid meets your vehicle specs.

Tips to Protect Your Car Coolant

Given the vital role antifreeze plays in engine longevity and performance, it pays to employ a few best practices:

Check strength and freeze protection level every couple of oil changes or at least once annually. Refractometers offer precise readings.
To maintain a 50/50 mix, add pre-mixed antifreeze rather than pure distilled water over time. This retains essential additive concentrations.
Thoroughly flush and replace coolant every 3-5 years or 30,000-50,000 miles per manufacturer guidelines. This cycle keeps corrosion protection fresh.
Stick with the current coolant to avoid contamination when adding any leaked fluid. Never top up with other formula types.
Watch for leaks around hose connections. Have minor seeps at clamps or weep holes addressed promptly before major component damage occurs.

Also read: Car engine heating

Conclusion

Modern engine cooling systems play a vital, often underappreciated role in daily and severe driving conditions. With temperatures ranging from below freezing through the blistering summer heat, the right water and antifreeze combination keeps your motor humming within safe limits. Choosing a formula designed to match metals and sealing materials under your hood will minimise corrosion over thousands of miles. With a quality coolant flowing through robust components, your ride will stay calm and collected for years of trouble-free journeys.

Frequently Asked Questions

Here are a few common questions and their answers related to the Car Coolant

Q1. What does a car's coolant or antifreeze do?

It regulates engine operating temperature by circulating fluid that absorbs heat from hot engine parts, cycling to the radiator, cooling, and returning to absorb more heat.

Q2. How does the coolant enable consistent engine temperature?

The 50/50 water and antifreeze mix flows through passages within the engine block, picking up damaging waste heat and bringing it to the radiator. There, it dumps the heat outside and then cycles back.

Q3. What ingredients and additives make antifreeze formulations?

Primary ingredients are water, ethylene glycol that regulates freezing/boiling points, and corrosion inhibitors to protect interior metal surfaces from rust and scale buildup.

Q4. What are the different types of auto antifreeze fluid available for cars?

The most prevalent options are IAT, OAT, and newer HOAT antifreeze and coolants. Each offers varying benefits for corrosion and deposit prevention.

Q5. Should I change my car's original factory coolant fluid type?

No, stick with the same coolant formula your car left the factory with, according to the original radiator cap, to avoid issues with additive compatibility.

Q6. How often should I drain and replace my car's engine coolant?

For most vehicles, manufacturers recommend flushing and refilling with fresh coolant every 3 to 5 years or between 30,000 to 50,000 miles of driving.

Q7. What does an overheating car engine indicate about the coolant?

It likely points to insufficient coolant circulation from a stuck thermostat, low fluid level allowing air pockets to reduce heat transfer, or a water pump not able to move coolant flow fast enough effectively.

Q8. How can I check the concentration or strength of existing antifreeze?

Use a refractometer antifreeze tester to accurately measure freeze point protection and concentration to ensure a proper 50/50 mix between antifreeze and distilled water for ideal protection and heat transfer.

Q9. What advice can help lengthen my vehicle’s coolant lifespan?

Check antifreeze strength yearly, use pre-mixed fluid for top-off rather than pure water, thoroughly flush the system based on mileage intervals, and address minor leaks immediately before major issues occur.

Q10. What indicates the coolant or water pump might need replacing soon?

Watch for visible leaks from housing seals and joints. Listen for bearing noises or observe weeping fluid indicating seals are failing internally, requiring replacement of worn components before catastrophic failure happens.

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