An overheating car is more than an inconvenience. If the temperature warning light comes on, the temperature gauge moves into the red, or steam starts coming from under the bonnet, you need to take action quickly.
Knowing what to do when your car overheats can help protect your engine and keep you safe at the roadside.
This is particularly important in London, where heavy traffic, stop-start driving and warm summer temperatures can put additional strain on a vehicle’s cooling system. A car that appears perfectly fine when moving freely may begin overheating when stuck in congested traffic.
The key rule is simple: don’t ignore the warning signs and don’t continue driving an overheating vehicle.
Why Do Cars Overheat?
Your engine produces a considerable amount of heat while running. The cooling system is designed to keep the engine within a safe operating temperature.
When something goes wrong with that system, the engine temperature can rise rapidly.
Common Causes of Engine Overheating
Several problems can cause a vehicle to overheat, including:
- Low coolant levels
- Coolant leaks
- A faulty radiator
- A damaged water pump
- A failed cooling fan
- A faulty thermostat
- Blocked cooling passages
- Problems with the head gasket
Sometimes the cause is relatively straightforward. However, overheating can also indicate a serious mechanical problem.
Why Hot Weather Can Make the Problem Worse
Warm weather doesn’t necessarily cause an otherwise healthy car to overheat, but high temperatures can increase the workload on the cooling system.
The risk can become greater when hot weather is combined with:
- Heavy traffic
- Long journeys
- Steep hills
- Towing or heavy loads
- Poor vehicle maintenance
- Low coolant levels
London’s frequent congestion can be particularly challenging because your engine continues producing heat while the vehicle is moving slowly or standing still.
How to Tell If Your Car Is Overheating
Recognising the early warning signs can help you act before serious damage occurs.
Warning Lights and Temperature Gauge
Your dashboard may provide an early warning.
Depending on the vehicle, you may see:
- A high-temperature warning light
- A coolant warning light
- A temperature gauge entering the red zone
- A dashboard message telling you to stop the vehicle
Never ignore these warnings.
If the temperature gauge is climbing unusually high, find somewhere safe to stop as soon as possible.
Steam, Strange Smells and Loss of Power
Other warning signs can include:
- Steam or vapour coming from under the bonnet
- A sweet smell from leaking coolant
- Unusual engine noises
- Reduced engine performance
- The air conditioning suddenly becoming less effective
- A burning smell
If you notice several of these symptoms together, treat the situation seriously.
What to Do When Your Car Overheats
If your engine temperature rises, follow these steps.
1. Stay Calm and Find a Safe Place to Stop
Your priority is safety.
If possible, move to a safe location away from moving traffic. If you’re on a busy London road, don’t make a sudden manoeuvre just to find the perfect parking spot.
If you’re on a motorway or dual carriageway, follow the appropriate breakdown procedure and get yourself and your passengers to a safe location.
2. Switch Off the Engine
Once you’ve stopped safely, switch the engine off.
Continuing to run an overheating engine can increase the temperature and potentially cause serious mechanical damage.
Don’t repeatedly restart the vehicle to see whether the problem has disappeared.
3. Let the Engine Cool Down
Give the engine plenty of time to cool.
Never open the bonnet immediately if there is significant steam coming from the engine compartment.
Hot coolant and steam can cause serious burns.
Allow the vehicle to cool naturally before attempting any checks.
4. Never Remove the Coolant Cap While Hot
This is one of the most important safety rules.
The cooling system can become pressurised when the engine is hot. Removing the coolant reservoir cap or radiator cap prematurely can release extremely hot coolant or steam.
Wait until the engine has cooled sufficiently before checking the system.
5. Check the Coolant Once the Engine Is Cool
Once the engine is cool, you can check the coolant reservoir.
If the level is below the recommended minimum, there may be a leak or another cooling-system problem.
Only use the correct coolant specified for your vehicle. Your owner’s handbook should provide the appropriate information.
If you’re unsure, don’t guess.
6. Look for Obvious Leaks
Once the vehicle has cooled, look around the engine bay and underneath the vehicle for signs of leaking fluid.
You may notice:
- A puddle underneath the car
- Wet areas around hoses
- Coolant around the reservoir
- Damage to a hose or radiator
Don’t touch hot components or attempt repairs at the roadside.
7. Call a Breakdown or Recovery Service
If the car has overheated significantly, professional assistance is often the safest option.
A breakdown or recovery technician can inspect the vehicle and determine whether it can safely continue or needs to be recovered to a garage.
For London drivers, professional recovery can be particularly useful when your vehicle has broken down in a busy or potentially dangerous location.
8. Do Not Continue Driving If the Problem Persists
If the temperature rises again after cooling down, stop driving.
An engine that repeatedly overheats needs to be inspected.
Trying to reach your destination could turn a relatively manageable cooling-system problem into major engine damage.
Can You Drive an Overheating Car?
Generally, you should not continue driving if your car is genuinely overheating.
Why Continuing to Drive Can Be Dangerous
An overheating engine can deteriorate rapidly.
Continuing to drive may result in:
- Engine failure
- Breakdown in traffic
- Loss of performance
- Damage to engine components
- A much higher repair bill
Even if the vehicle appears to be running normally, an elevated engine temperature shouldn’t be ignored.
Potential Engine Damage
Severe overheating can damage important components, including the cylinder head, head gasket, and other internal engine parts.
In extreme cases, an overheated engine may require extensive repairs or replacement.
That’s why knowing what to do when your car overheats can save you considerably more than simply waiting until the engine fails.
What Causes Cars to Overheat in London?
Stop-Start Traffic
London’s traffic can place significant demands on your vehicle.
During prolonged congestion, the engine continues generating heat while the car moves slowly. The cooling fan becomes particularly important in these conditions.
If the fan isn’t working correctly, temperatures can rise.
Low Coolant and Cooling System Problems
Coolant helps transfer heat away from the engine.
If the coolant level is low because of a leak or another fault, the cooling system may not be able to regulate engine temperature effectively.
Faulty Radiators, Fans and Thermostats
A problem with any major cooling-system component can contribute to overheating.
For example:
- A blocked radiator may struggle to dissipate heat.
- A failed cooling fan can cause problems in slow traffic.
- A faulty thermostat can disrupt coolant circulation.
- A damaged water pump can prevent effective coolant circulation.
A professional inspection is the best way to identify the underlying cause.
How to Prevent Your Car From Overheating
Prevention is usually much cheaper than repairing an overheated engine.
Check Coolant Levels
Check your coolant level regularly, particularly before long journeys and during periods of hot weather.
Always check it according to the manufacturer’s instructions and only when the engine is cool.
Maintain Your Vehicle
Regular servicing can help identify cooling-system problems before they result in a breakdown.
Ask your garage to check relevant components such as:
- Coolant condition
- Radiator
- Hoses
- Cooling fan
- Thermostat
- Water pump
Check the Cooling System Before Long Journeys
Before travelling outside London, particularly on a summer holiday, carry out some basic checks.
Make sure:
- Tyres are correctly inflated
- Coolant is at the correct level
- Engine oil is sufficient
- Windscreen washer fluid is topped up
- Warning lights aren’t showing
A few minutes of preparation could save hours waiting for roadside assistance.
What to Do If Your Car Overheats on a Motorway
Motorway breakdowns require extra caution.
If your car starts overheating:
- Leave the motorway at the next safe opportunity if possible.
- If you cannot, move towards the left-hand side or hard shoulder where appropriate.
- Switch on your hazard warning lights.
- Stop somewhere safe.
- Get yourself and passengers to a safe location when it is safe to do so.
- Contact your breakdown provider or the appropriate emergency service.
- Do not attempt repairs in a dangerous position.
If you have broken down in a live traffic environment and you’re unable to reach a safe place, prioritise your personal safety and follow official emergency guidance.
FAQs About Overheating Cars
1. How long should I wait before opening the bonnet?
If the engine is very hot or steam is coming from underneath the bonnet, wait until it has cooled significantly before opening it. Never remove a coolant or radiator cap while the system is hot and pressurised.
2. Can I pour cold water into an overheated engine?
Avoid pouring cold water over a hot engine. A sudden temperature change can potentially damage components. Allow the engine to cool and follow the vehicle manufacturer’s guidance.
3. Can low coolant cause a car to overheat?
Yes. Insufficient coolant can prevent the cooling system from removing enough heat from the engine.
4. Why does my car overheat in traffic but not on the motorway?
A cooling fan or another part of the cooling system may not be operating correctly. At higher speeds, airflow through the radiator can provide additional cooling, while slow traffic places greater reliance on the cooling fan.
5. Can I drive after my car has overheated?
It depends on the cause and the vehicle’s condition. If the temperature has reached the red zone or the vehicle has produced significant steam, it’s safest to have it professionally inspected rather than continuing your journey.
6. How can I prevent my car from overheating in summer?
Maintain the cooling system, check coolant levels, keep up with servicing, and pay attention to temperature warnings. If you notice anything unusual, have the vehicle checked before taking a long journey.
Conclusion
Knowing what to do when your car overheats can protect both you and your vehicle.
The most important steps are to stop safely, switch off the engine, allow it to cool, and never remove the coolant cap while the engine is hot. If the vehicle continues to overheat or you notice steam, leaks, or other serious symptoms, don’t risk driving further.
For London motorists, an overheating vehicle can be especially stressful when you’re stuck in traffic or stopped on a busy road. Having a reliable vehicle recovery service available can give you peace of mind when things don’t go according to plan.
White Recovery provides professional vehicle recovery assistance for motorists who find themselves dealing with breakdowns and unexpected vehicle problems across London and surrounding areas. If your car overheats and you’re unsure whether it is safe to continue driving, getting professional recovery assistance can help you avoid further damage.
When in doubt, it’s better to stop and seek professional help than risk turning a cooling-system problem into a major engine repair.