Why Your Car's Coolant Matters More on a Hot Summer Drive

An Irish summer might not sound extreme, but a warm day, a fully loaded boot and slow traffic on the M50 can put serious pressure on your engine. If the coolant level is low or the cooling system isn’t working properly, the temperature can climb faster than many drivers expect, potentially leading to an overheated engine.

That’s why coolant deserves a place near the top of your summer vehicle maintenance list. A quick check before a drive from South Dublin to Galway, Wexford or the west coast could prevent car overheating, costly repairs and a long wait at the roadside.

What Does Engine Coolant Actually Do?

Coolant is one of the most important car fluids under the bonnet. It circulates through the engine components and radiator, carrying excess heat away so the engine can operate within its designed engine temperature range.

It does more than protect your car engine in cold weather. The correct coolant mixture, which includes antifreeze, also raises the fluid’s boiling point and contains additives that help protect internal components against corrosion and deposits such as dirt. Coolant lowers the freezing point of water well below 32°F and raises the boiling point above 212°F.

Your cooling system includes the radiator, expansion tank, hoses, thermostat, water pump and cooling fan. The radiator acts as a heat exchanger, transferring heat from the hot coolant to the ambient air. A clean radiator improves cooling efficiency, and cleaning radiator fins can further enhance this effect. Freeze plugs seal openings in the engine block and heads, while the radiator overflow tank collects excess coolant during operation. If any part of that entire system develops a leak or fails, the engine may struggle to control its temperature.

Engine coolant is typically composed of ethylene glycol or propylene glycol. Different coolant types (IAT, OAT, HOAT) use varying additive packages to prevent corrosion.

Why Hot Summer Drives Put More Pressure on the Cooling System

Engines always generate heat. On a warm summer drive, however, the radiator has less temperature difference to work with, while air conditioning, heavy loads, long climbs and stop-start traffic can add to the demand.

Picture a bank-holiday Friday on the M50 or a slow crawl through Dublin city with the air conditioning running. There may be less airflow through the radiator than there is on an open road, so the electric fan and the rest of the cooling system have to work harder under these high temperatures.

AA Ireland says overheating is one of the common hot-weather problems its patrols encounter. Low coolant levels, leaking hoses, broken electric cooling fans and low fluid levels in transmission fluid, brake fluid, power steering fluid, and differential fluid are among the issues that can leave drivers stranded.

In our experience, a hot day rarely creates a healthy car’s first fault. More often, it exposes a small existing issue, such as a slow leak, an ageing hose, a weak radiator cap or a fan that’s no longer operating reliably.

Check coolant levels every month during summer to stay ahead of potential overheating engine issues.

Signs Your Car May Be Low on Coolant

Low coolant doesn’t always announce itself with a dramatic cloud of steam. The early signs can be easy to dismiss, particularly on short journeys around Terenure, Rathfarnham or Dundrum.

You might notice the temperature gauge reading higher than usual or a red temperature warning appearing on the dashboard. Steam from under the bonnet is an obvious warning, but a sweet smell inside or outside the car can also point to leaking coolant.

Other signs include coloured residue around the engine bay, a puddle beneath the car, cabin heating that suddenly blows cold or a cooling fan that seems to run unusually often.

A coolant level that repeatedly drops after being topped up also needs attention. The fluid is going somewhere, so don’t keep refilling the reservoir and hoping for the best.

How to Check Your Coolant Level Safely

Only check the coolant when the engine is completely cold and the car is parked on level ground. A hot cooling system is pressurised, and opening the cap can release scalding fluid and steam.

Find the Expansion Tank

The translucent coolant reservoir is normally marked with minimum and maximum lines. Your owner’s manual will show its exact location if you’re unsure.

Read the Level From Outside

When the engine is cold, the fluid should sit between the minimum and maximum marks. You shouldn’t need to remove the cap simply to inspect the level.

Check the Condition as Well as the Quantity

Look for obvious contamination, oily residue or unusual discolouration. Coolant colour alone doesn’t reliably identify its specification, so don’t choose a replacement simply because it looks similar.

Use the Correct Product

Always follow the manufacturer’s coolant specification and dilution instructions. Mixing incompatible products can reduce protection or create deposits, while plain water doesn’t provide the same boiling, freezing or corrosion protection. It is recommended to use distilled water for diluting concentrated coolant.

If you’re unsure what your Suzuki Vitara, Swift or S-Cross requires, check the owner’s handbook or ask a trained technician. The Gerry Caffrey Motors service team in Terenure can inspect the system and identify a leak before it becomes a bigger problem.

Coolant Replacement and Maintenance

For optimal performance, replace your engine coolant every 2 years. Different coolant types exist, including Inorganic Additive Technology (IAT) for older vehicles, Organic Acid Technology (OAT) for modern vehicles lasting up to 5 years, and Hybrid Organic Acid Technology (HOAT) which combines features of both. Never mix different coolant types as this can damage the radiator or water pump.

What to Do If Your Engine Starts Overheating

If the temperature warning light comes on, the gauge moves into the red or you see steam, treat it seriously. Turn off the air conditioning and pull over somewhere safe as soon as possible.

Switch off the engine and keep yourself and your passengers clear of moving traffic. Don’t open the coolant reservoir or radiator cap while the engine is hot. Never pour cold water on a hot engine as the sudden temperature change could cause parts of the engine block or other engine components to crack.

Allow the car to cool fully, which may take at least 30 minutes, and contact roadside assistance or a tow truck if you’re uncertain about its condition. Don’t continue driving simply because the warning disappears after a few minutes.

Driving an overheating car can turn a manageable leak or failed component into a damaged cylinder head, head gasket or engine block. If steam is heavy, coolant is pouring out or the car has lost power, arrange recovery instead of attempting to drive to a garage.

Keep a first aid kit or aid kit in your vehicle for emergencies, especially on long drives.

A Simple Summer Vehicle Maintenance Check

Coolant is essential, but it’s only one part of preparing for a longer Irish road trip. Before leaving, take a few minutes to check the car as a whole.

With the engine cold and the car on level ground, inspect the coolant and engine oil. Engine oil lubricates moving parts to reduce friction and heat. Top up the windshield washer fluid and examine the wiper blades for wear or damage.

Look for wet patches, staining, damaged hoses or loose connections under the bonnet. Confirm that no warning lights remain on after starting the engine.

Around the car, check the tyre pressures while the tyres are cold and inspect the tread depth and sidewalls for damage.

Test the lights, indicators, air conditioning and demisting system. If you’re packing for a family holiday, secure the luggage properly and avoid exceeding the car’s recommended load limits.

We often see drivers focus on getting a car through its NCT and assume everything else has been covered. The NCT is an important roadworthiness check, but it isn’t a substitute for scheduled servicing or a cooling-system diagnosis.

Keeping service invoices and maintenance records also helps when it’s time to trade in. A documented cooling-system repair is far more reassuring to the next owner than a history of unexplained coolant top-ups.

Coolant Checks When Buying a New or Used Car

A new Suzuki gives you the reassurance of a known maintenance schedule from day one. Whether you choose the city-friendly Swift, the practical Vitara or the spacious S-Cross, following the recommended service intervals and using the correct car fluids will help protect its reliability.

A carefully selected used car can offer excellent value, but its condition and service history matter. Check for a stable coolant level, clear maintenance records, no overheating warnings and no signs of dried coolant around the hoses or expansion tank.

At Gerry Caffrey Motors, Dublin drivers can compare new Suzuki models with a curated range of premium used stock. This makes it easier to consider the benefits of a new car against the potential value of a well-maintained used vehicle.

If you’re comparing an Irish car with a personal import, remember to consider the complete landed cost. VRT and current Revenue rules can significantly affect what appears to be an attractive purchase price.

A strong trade-in can also reduce the amount you need to finance. The Gerry Caffrey Motors team can help you explore finance options and assess whether it makes more sense to maintain your current car or replace it with a newer Suzuki.

Frequently Asked Questions About Car Coolant

Can I Use Water Instead of Coolant in Summer?

Plain water doesn’t provide the same boiling-point, freezing and corrosion protection as the correct coolant mixture. Use the specification stated in your owner’s manual and seek professional attention if you don’t know what is already in the system.

How Often Should I Check the Coolant Level?

Check the level regularly when the engine is cold and always before a long journey. If it drops more than once, arrange an inspection because a sealed, healthy cooling system shouldn’t need frequent top-ups.

Does Air Conditioning Cause Engine Overheating?

Air conditioning adds load to the engine, but a healthy cooling system should manage it. If the temperature rises whenever the air conditioning is running, there may be an underlying fault with the fan, coolant flow or another component.

Will an NCT Identify a Coolant Leak?

An obvious leak may be noticed during an inspection, but an NCT isn’t a full mechanical diagnosis or a replacement for servicing. If you smell coolant, see residue or notice the level falling, arrange a cooling-system check rather than waiting for the test.

Is It Safe to Drive With a Low Coolant Warning?

Don’t ignore a low coolant warning. Stop safely, let the engine cool completely and follow the guidance in the owner’s handbook.

If the coolant level is very low, the engine is overheating or there’s an obvious leak, contact roadside assistance or a garage.

Keep Your Suzuki Ready for the Irish Summer

A two-minute cold-engine check can protect your car from one of summer driving’s most expensive risks. Keep an eye on the coolant level, respond quickly to warning signs and have repeated coolant loss investigated.

Thinking about upgrading to a Suzuki? Visit Gerry Caffrey Motors in Terenure, Dublin 6W, to explore the Vitara, Swift and S-Cross, discuss your trade-in or find a finance option that suits your next move.