Why is my car engine overheating?

Problems with an overheating engine are some of the most serious a driver can face. If ignored, they can result in engine damage costing thousands of pounds to replace or repair, or worse still, depending on the age and value of the car, not worth repairing at all.

When the engine temperature is dangerously high, don’t take any risks driving it to your mechanic; have it towed or collected. The drive may only be a mile or two, but that’s often enough to seize an engine under the wrong circumstances; it could be the most expensive drive you ever take in your car.

What are the common causes of an overheating car engine?

Not enough or no coolant

Risk level – High

What to do – Fill the coolant reservoir with the correct coolant for your car.

The first thing to check when your temperature gauge is heading into the red is your coolant level. If there isn’t enough coolant to keep your engine at a safe temperature, it can’t do its job. Make sure that the level of coolant is well within the recommended limits.

The cooling system is leaking

Risk level – High

What to do – Repair the leak or replace the leaking component.

You should be able to spot obvious signs of a leaky cooling system by puddles of coloured liquid underneath the engine bay of your car. You might be able to trace the leak by following the path of dripping coolant to damaged hoses or other faulty components.

To differentiate a cooling system leak over other types, coolant is coloured and has a sweet smell; the most common tints are green, blue and orange, depending on the type required by your car.

The water pump has failed

Risk level – High

What to do – DO NOT DRIVE. Replace the water pump immediately.

A broken water pump delivers several associated problems—all severe. In many cases, a failed water pump can kill your car; don’t risk driving it; get it replaced safely and as soon as possible.

There’s a problem with the radiator or radiator fan

Risk level – High

What to do – Repair or replace the radiator.

The radiator is full of tiny fins and channels designed to remove the heat from the coolant. If the radiator is leaking, blocked, or the fan isn’t blowing cool air over it, then it’s likely to lead to problems with the heat in your engine.

The thermostat has failed

Risk level – High

What to do – Replace it immediately.

Your thermostat’s job is to regulate engine temperature. If it isn’t working properly or has broken completely, then your engine temperature could be swinging all over the place, ultimately too high, and leading to irreparable damage.

What should I do if my engine is overheating?

• Pull over as soon and as safely as possible.

• Turn off the engine ASAP.

• If you can’t pull over, turn the heaters and fans up full, and open the windows to dissipate the heat.

• Keep a steady airflow around the engine to give it its strongest chance of cooling down once parked, but be extremely careful if you choose to lift the bonnet. You should allow your car to stand before popping the hood to let the worst of the heat clear and the engine begin cooling.

• Call for assistance.

Things you should do when your engine overheats

Only if the temperature rise is slow and remains under the dangerous limit of your temperature gauge should you continue to drive the car.

If you choose to keep moving, you should regularly monitor the level of coolant. If you don’t have the correct coolant at hand, you can use water to top it up during your emergency.

If you must keep driving, don’t put any unnecessary stress on the engine. Drive at as slow a speed as is safely possible and with your hazard warning lights on. Try not to brake too much as brake drag increases the load on the engine.

When you stop in traffic, shift into neutral and rev the engine slightly. This will encourage the water pump and fan to speed up, drawing more coolant through the radiator.

How can I prevent my engine from overheating?

• Regularly check all fluid levels (especially the coolant!), radiator condition, and timing belt.

• Service your car regularly.

• Replace the timing belt and water pump at the appropriate mileage.

• Store an extra bottle of coolant and water in your boot in case of emergencies.

• Monitor the temperature gauge while driving.

• Ensure all liquids are topped up when driving on the hottest days.

• Limit air conditioning use in extreme heat.

What are the signs of an overheating engine?

An overheating engine will trigger warning lights on your dashboard, and also the temperature gauge will rise toward the danger level at the red end of the scale.

You may see smoke or steam rising from underneath the car bonnet, and the car may also drive poorly compared to normal.

How much does it cost to fix an overheating engine?

Topping up your coolant is a cheap and easy fix for a basic issue, whereas replacing a seized engine can cost thousands of pounds. Understanding where the problem lies will give you a better idea of the price of the required repairs.

If your car is running hot and you can’t spot a leak, then one of our trusted mechanics can visit you to check the vehicle over. Book in with Fixter, and we’ll run a diagnostic test to uncover the issue. Once we know where the problem is, we’ll run you through all the solutions and their costs.