Why is Your Engine Overheating? What should I do if my car is overheating?

Car overheating is more than just an inconvenience - it can leave you stranded on the side of the road and cost you thousands in repairs. For UK drivers, it's important to understand what overheating means, how to recognise the signs early, and most importantly, what actions to take. This guide is tailored to help beginners and everyday car owners understand everything about engine overheating in a clear and practical way.

What Is Engine Overheating?

Engine overheating refers to a situation where the car's engine becomes hotter than it's designed to handle. Modern car engines run best at a certain temperature range, usually between 90°C and 105°C. When temperatures exceed this range, it can cause severe damage to parts like the head gasket, pistons, and cylinders.

This rise in temperature usually indicates that something in the cooling system isn't working correctly - whether that's the engine coolant itself, the radiator, or another related component.

Why Is My Car Overheating? (Common Causes)

Car overheating is usually caused by a fault in the engine's cooling system. The most common reasons include low coolant, leaks, thermostat failure, or radiator and water pump issues.

1. Low Coolant Levels

Low coolant is the most common reason your car overheats. Coolant absorbs heat from the engine and moves it to the radiator. If coolant levels drop-due to leaks or evaporation-the engine can't cool down properly.

2. Cooling System Leaks

Leaks from radiator hoses, the radiator itself, or the water pump can cause coolant to escape. Even small leaks reduce pressure in the system, leading to poor circulation and overheating.

3. Faulty Thermostat

The thermostat controls coolant flow. If it gets stuck shut, hot coolant stays in the engine, causing it to overheat quickly. This is a common fault in colder UK weather.

4. Failing Water Pump

The water pump keeps coolant moving through the engine. If it fails or becomes blocked, coolant can't circulate, and the engine temperature rises rapidly.

5. Radiator Issues

A blocked, damaged, or leaking radiator can't cool the engine effectively. If the radiator fan isn't working-especially when idle or in traffic-the engine will overheat.

6. Damaged or Worn Hoses

Rubber hoses in the cooling system can crack, wear out, or disconnect over time. This causes coolant to leak or flow inefficiently, leading to overheating.

7. Low Engine Oil

Oil reduces friction and helps with heat dissipation. Low oil levels increase engine heat and can worsen overheating-even with a full coolant system.

8. Air Trapped in the Cooling System

Air pockets can block coolant flow. This often happens after a coolant refill or flush and may cause uneven cooling or sudden overheating.

9. Blocked Coolant Passages

Rust, debris, or sludge buildup can clog coolant pathways in the engine or radiator. This limits coolant flow and causes heat to build up.

10. Blown Head Gasket

A blown head gasket can let coolant leak into the engine cylinders or oil system. This not only causes overheating but can also result in serious engine damage.

In colder UK months, issues like a stuck thermostat or incorrect coolant mix can also lead to overheating.

Signs Your Car Is Overheating

Car overheating often shows clear warning signs that drivers in the UK should never ignore. Spotting these symptoms early can help prevent severe engine damage and costly repairs. Here are common symptoms:

1. Temperature Gauge in the Red

One of the first signs of engine overheating is the temperature gauge rising into the red zone or displaying an "H" (hot) symbol. This means your engine is running dangerously hot.

2. Steam or Smoke from the Bonnet

If you see steam or white smoke coming from under the bonnet, especially near the radiator, it's a serious indicator that your engine is overheating and coolant may be boiling.

3. Dashboard Warning Lights

Modern cars display warning lights when the engine is overheating-typically a red thermometer or coolant symbol. Don't ignore these alerts; they signal immediate attention is needed.

4. Burning or Sweet Smells

A strong, sweet smell can mean coolant is leaking and evaporating. A burnt odour may point to overheated oil or electrical components. Both are signs of engine trouble.

5. Unusual Noises from the Engine

Clicking, knocking, or hissing sounds under the bonnet can mean that parts are expanding, coolant is leaking, or steam is escaping-common with overheating engines.

6. Reduced Engine Power

If the engine feels sluggish or loses power, it may be going into "limp mode" to protect itself from heat damage.

7. Extremely Hot Bonnet

The bonnet may feel unusually hot to the touch. While it's normal for it to get warm, excessive heat can indicate that the engine is overheating underneath.

If you notice any of these signs, it's important to act quickly and safely pull over.

What to Do When Your Car Overheats?

If your car starts overheating while driving in the UK, stay calm and follow these steps to avoid further damage or injury. Acting quickly and safely can save you from expensive repairs and roadside danger.

1. Pull Over Safely

As soon as you notice signs like steam, a high temperature gauge, or dashboard warnings, pull over to a safe spot, turn on your hazard lights, and stop the car.

2. Turn Off the Engine

Immediately switch off the engine. This stops it from generating more heat and helps prevent permanent engine damage.

3. Turn On the Heater (Optional Tip)

If it's safe to do so, turn your car's heater to full blast. This can help draw some heat away from the engine into the cabin. You might feel uncomfortable, but it can temporarily reduce overheating.

4. Don't Open the Bonnet Right Away

Avoid opening the bonnet immediately. The engine bay can be extremely hot, and steam or boiling coolant may be under pressure. Wait at least 30 minutes before lifting the bonnet.

5. Let the Engine Cool Down

Give the engine enough time to cool-30 minutes or more depending on conditions. This is crucial before checking anything under the bonnet.

6. Check Coolant Levels

Once it's safe, check the coolant level in the reservoir (not the radiator cap). If coolant is low and you have some with you, top it up. If you only have water, it's okay to use it temporarily until the issue is fixed.

7. Don't Keep Driving If the Issue Persists

Do not continue driving if the engine keeps overheating or you're unsure what's wrong. It could cause major damage to the engine.

8. Call a Breakdown Service

If you're unsure what to do next, it's safer to arrange professional breakdown assistance. Driving an overheating vehicle can lead to serious and expensive engine damage.

With Warranty Direct, you can count on reliable cover that includes breakdown support and protection against unexpected repair costs. If your vehicle won't cool down or restart safely, use your policy to get expert help or towing to a trusted garage.

What Not to Do When Your Engine Overheats?

When your car overheats, avoid these dangerous mistakes:

• Don't keep driving: Continuing to drive can cause irreversible engine damage.
• Don't open the radiator cap while hot: It's under pressure and can spray boiling coolant, causing severe burns.
• Don't pour cold water on the engine: It can cause the engine block to crack due to rapid temperature change.
• Don't ignore the issue: Overheating can lead to expensive repairs if not dealt with immediately.

How to Check Your Engine Coolant

Checking your coolant is simple and part of regular maintenance. Here's how:

• Wait for the engine to cool down completely.
• Open the bonnet and locate the coolant reservoir - it's usually a translucent plastic tank with 'min' and 'max' lines.
• Check the level: The fluid should be between the two lines. If it's low, add a 50:50 mix of coolant and distilled water (or pre-mixed coolant).
• Never overfill: Stick to the 'max' line. Close the cap tightly.

For a detailed explanation on coolant types, top-up tips, and signs of coolant problems, read our complete car coolant guide.

What Does the Temperature Warning Light Mean?

If your temperature warning light comes on (usually red or amber), it means your engine is too hot.

• Amber: A warning that something might be wrong - check coolant and fan operation.
• Red: Indicates an urgent issue. You should stop the car immediately and follow the steps to cool the engine.

UK cars often also have a coolant level warning light, shaped like a thermometer or coolant tank. Don't ignore these warnings - they are early signs of trouble.

Want to know the common causes of the engine temperature warning light and how to fix them? Read our full guide on engine temperature warning light causes and fixes for simple, expert tips.

How Long Does It Take for an Overheated Engine to Cool Down?

It usually takes 30 minutes to an hour for an overheated engine to cool down fully. Factors such as outside temperature, engine size, and airflow affect cooling time.

During this time:

• Don't try to check under the bonnet.
• Avoid opening the radiator cap.
• Wait until it's safe to assess the coolant level or call for help.

How to Prevent Car Engine Overheating

Preventative maintenance is key to avoiding overheating. Here are some tips:

• Regularly check coolant levels (monthly or before long journeys)
• Inspect for leaks under the car and around the radiator
• Flush your radiator every 2-3 years or as per the car manufacturer's schedule
• Check your thermostat and fan operation during servicing
• Book regular servicing - especially before summer road trips or long drives

These steps can reduce the risk of overheating.

What Damage Can an Overheating Engine Cause?

Overheating can cause significant and costly damage to your car, such as:

• Warped cylinder head: Affects engine compression and performance
• Blown head gasket: Coolant and oil can mix, causing engine failure
• Cracked engine block: One of the most expensive repairs
• Melted plastic or rubber components: Hoses, belts, and sensors may fail

Repairs from overheating can range from £500 to over £3000, depending on the damage.

Is It Safe to Drive an Overheating Car?

No, it is not safe to drive an overheating car. Even driving a short distance can cause severe damage. If your engine is overheating:

• Stop the car immediately
• Follow safety procedures to let it cool
• Call for roadside assistance if the issue isn't resolved

In some cases, you may need to be towed to a garage.

Troubleshooting an Overheated Engine

If your car frequently overheats, try this basic troubleshooting:

• Check coolant level and quality
• Look for visible leaks
• Listen for the cooling fan - does it turn on?
• Observe if overheating happens only in traffic (could indicate fan or airflow issues)
• Have a mechanic inspect the radiator, thermostat, and water pump

For UK car owners, getting an annual MOT and interim service helps catch cooling issues early.

FAQs

Q1: Can I use water instead of coolant?

Yes, but only in an emergency and only with distilled water. Replace it with proper coolant as soon as possible.

Q2: Is engine overheating covered by warranty?

It depends on your warranty. Some extended car warranties in the UK cover cooling system faults.

Q3: How often should I check coolant levels?

Ideally once a month or before any long trip.

Q4: What colour should coolant be?

Usually pink, red, orange, or green - it varies by manufacturer. A rusty or cloudy colour means it's time to flush the system.

Conclusion

Car overheating is a common yet manageable issue when addressed early. With regular maintenance and a good understanding of your vehicle's warning signs-like rising engine temperatures or low coolant-you can often prevent breakdowns before they happen. Whether you're a daily commuter or a weekend driver on UK roads, staying proactive helps you avoid costly repairs and keeps your journeys safe and stress-free.

For added peace of mind, having a reliable extended car warranty and roadside assistance can make all the difference when things go wrong. At Warranty Direct, we offer comprehensive warranty cover and optional UK breakdown assistance to help you handle issues like engine overheating without the stress.

Explore our car warranty plans and see how Warranty Direct keeps you covered every mile of the way.