Modern car engines are built to last, but they still rely on many complex systems working together properly. When something goes wrong with the oil, cooling, or timing, the engine can stop running or get damaged.
But don’t worry, many of the top causes of engine failure can be prevented with regular maintenance and simple checks that you can do at home.
Below are some of the main reasons why a car engine might fail, and what you can do to reduce the risk of it happening to you.
What causes engine failure?
Car engine failure can be caused by a lack of regular maintenance that allows small issues to develop. Overheating, low oil levels (or poor oil quality), fuel system problems, and issues with the cam belt are common when it comes to engine failure.
1. Low or contaminated engine oil
Engine oil is designed to keep the moving parts inside an engine lubricated. It forms a thin film between moving parts (such as pistons, crankshaft bearings, and camshafts), helping control the heat generated by friction.
If your engine oil level drops too low (or if the oil becomes contaminated with debris), these parts can start to wear quickly and, in some cases, even overheat and seize.
Preventing oil-related engine issues
For good engine oil health and a smooth-running engine, you should:
- Regularly check your engine oil levels with a dipstick and keep an eye out for leaks
- Follow the recommended oil change intervals in your vehicle handbook (typically every 5,000 – 7,5000 miles)
- Always use the correct oil specification for your car’s engine
- Investigate any warning lights or oil pressure alerts as soon as you can. If you’re not sure, take your car to a professional for help.
2. Engine overheating
Engines naturally operate at high temperatures and rely on a cooling system to keep their heat levels under control. If the system fails, the engine temperature can rise quickly. When an engine overheats, metal parts can expand beyond their normal limits, damaging the cylinder head gasket or causing internal components to warp. Overheating can be caused by:
- Low coolant levels
- A failed water pump
- A blocked radiator
- A faulty thermostat
Avoiding your engine overheating
Keeping your engine at a normal temperature is essential. To do this, you should:
- Check your coolant levels periodically
- Look for coolant leaks under your vehicle
- Keep an eye on the temperature gauge while driving
- Make sure that your regular service includes cooling system inspections
If the temperature warning light appears while you’re driving, it’s best to stop and investigate the cause before continuing.
3. Cam belt problems
Inside your engine, the camshaft and crankshaft must stay perfectly synchronised for things to run smoothly. This timing makes sure the engine’s valves open and close at the correct moment during each cycle. In many vehicles, this timing is controlled by a cam belt (also known as a ‘timing belt’).
If the belt breaks or slips, the engine can lose its timing. Sometimes, this can even allow the pistons and valves to collide, which can cause significant internal damage.
Reducing the risk of cam belt problems
Cam belts wear over time and must be replaced at the manufacturer’s recommended interval. To look after your cam belt, you should:
- Follow the recommended service schedule for cambelt replacement (anywhere from 40,000 – 100,000 miles)
- Ask a mechanic to check your belt’s condition during servicing
- Listen for unusual noises from the front of your engine that could indicate belt issues
Replacing a worn timing belt is far less costly than repairing damage caused by a failed one.
4. Ignition system faults
Your car’s ignition system is responsible for igniting the air–fuel mixture inside the engine’s cylinders. In petrol cars, spark plugs create the spark, while ignition coils supply the high voltage needed for this to happen at the correct moment.
Diesel cars don’t use spark plugs. Instead, they rely on high compression to ignite the fuel.
If parts of the ignition system in a petrol engine wear out or fail, the engine may misfire. This means one or more cylinders are not firing properly, which can lead to rough running, reduced power or the engine stalling.
Common causes include worn spark plugs, failing ignition coils or faulty sensors that affect how the engine controls combustion.
Preventing ignition system faults
To reduce the risk of any issues with the components that make up your engine’s ignition system, try to:
- Replace spark plugs at the intervals recommended by the manufacturer (ranging from 20,000 – 150,000 miles, depending on the quality)
- Have your ignition coils checked if your engine begins to misfire
- Investigate engine warning lights promptly
- Ask that routine servicing include ignition system checks
5. Fuel system issues
For an engine to run smoothly, it needs a steady supply of clean fuel delivered at the correct pressure. The fuel system includes components such as the fuel pump, fuel injectors, fuel filter and associated sensors.
If any part of this system becomes blocked or fails, the engine may not receive the fuel it needs. This can result in poor performance, difficulty starting or the engine stopping altogether.
Contaminated fuel or clogged injectors can also reduce how efficiently the engine operates.
Fuel tips for a healthy engine
- Get your fuel filter replaced at the recommended service interval (around 30,000 miles)
- Avoid running your car on very low fuel levels for long periods
- Use good-quality fuel from reputable filling stations
- Get fuel system issues checked if the engine struggles to start or loses power
How to prevent engine failure
While engines are highly complex, keeping on top of maintenance is relatively simple. And the good news is that engine problems often develop gradually, rather than all at once. So, paying attention to routine maintenance and early warning signs can make a big difference.
This means checking your coolant and oil levels often, getting regular servicing, paying attention to warning lights and replacing parts when needed.
Does breakdown cover include engine failure?
Most standard breakdown cover policies will include assistance with engine failure and related issues. This usually takes the form of roadside assistance, national recovery or onward travel.
Keep your car running smoothly
Looking after your engine and other crucial car components is key to a healthy vehicle that won’t break down on you unexpectedly. You can access more tips and expert advice on keeping your car in the best condition possible on the Green Flag blog.