Otto Explains — Engine Temperature
2 min read · 4 questions
My Car Is Overheating — What Should I Do?
Otto's short answer
If your temperature gauge reaches the red zone or the temperature warning light comes on, pull over safely and turn the engine off immediately. Do not continue driving. Engine damage from overheating can occur within minutes of the warning. Wait for the engine to cool before inspecting anything under the bonnet.
What should I do the moment my car starts overheating?
Pull over to a safe location as quickly as possible and turn the engine off. Do not open the radiator or coolant cap while the engine is hot. The coolant is under high pressure and can cause serious burns when released.
Do not pour cold water on a hot engine or radiator. If you are in traffic and cannot stop immediately, turn the heater on to maximum. This draws heat away from the engine by using the heater matrix as a secondary radiator. Call for assistance rather than attempting to drive further.
Why is my car overheating?
Common causes include: low coolant level from a leak (which can be slow and go unnoticed), a failed thermostat stuck in the closed position restricting coolant flow, a failed water pump unable to circulate coolant, a blocked or leaking radiator, a failed cooling fan (many modern vehicles have electric fans that can fail without warning), or a failing head gasket allowing combustion gases into the coolant system.
In Oman's climate, coolant condition and level are worth checking at every service, because a slow leak or degraded coolant is far easier to deal with before it causes overheating.
Still unsure? Ask Otto about your car.
Can the temperature gauge rise without the car actually overheating?
Yes. A faulty coolant temperature sensor can cause the gauge to read incorrectly when the engine is not overheating. However, it is always safer to treat an elevated temperature reading as a real overheating event until diagnosed. A temperature gauge that rises then comes down intermittently is a warning sign. This pattern often indicates a thermostat beginning to stick, a coolant level that is borderline, or early signs of a head gasket issue allowing gases into the system.
What damage can overheating cause to my engine?
Overheating causes damage roughly in order of severity and time: warped cylinder head from thermal stress, blown head gasket (allows coolant to mix with oil, or combustion gases to enter the cooling system), and cracked cylinder head or block. A blown head gasket is a significant and expensive repair. A cracked block often means engine replacement. That is why you should stop at the first warning: severe damage becomes far more likely if the engine keeps running after it appears.
Common Questions
What drivers also ask.
If you have no coolant, clean water can be used as a temporary measure to reach help, but only once the engine has cooled down completely. Never open the radiator or reservoir cap on a hot or warm engine: the system is pressurised and can release scalding coolant. Add the water slowly, and don't continue driving if the temperature rises again or the coolant is leaking away quickly. Water alone does not have the corrosion inhibitors and boiling point advantages of coolant, so the system should be properly flushed and refilled with the correct coolant as soon as possible.
This pattern is commonly caused by a failing electric cooling fan. At highway speed, airflow through the radiator keeps the engine cool. In slow traffic, the fan is needed to pull air through the stationary radiator, so if it is failing or not operating, the temperature rises. It can also indicate a coolant level that is borderline, or a partially blocked radiator.
The head gasket seals the cylinder head to the engine block. It keeps combustion pressure in the cylinder, oil in the oil galleries, and coolant in the water passages, and prevents any of these from mixing. Overheating causes the cylinder head to expand unevenly and can deform or crack the gasket. Once a head gasket fails, coolant may enter the combustion chamber (white exhaust smoke), oil may contaminate the coolant (milky oil), or compression may drop significantly.
Coolant degrades over time: the inhibitors that protect the system from corrosion break down and the pH changes. Intervals vary widely between vehicles and coolant types. Some are specified at around two years, while many modern long-life coolants are rated for considerably longer, so follow the interval and coolant type in your vehicle's service schedule. In Oman's conditions, where the cooling system works harder year-round, sticking to that interval is particularly important.
Yes. A single overheating event can cause damage that is not immediately obvious, particularly early head gasket deterioration. It also means the cooling system has a fault that has not been identified. A cooling system inspection after any overheating event confirms whether damage occurred and identifies the cause to prevent it happening again.
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