Summer heat and city traffic are the two biggest risk factors for an engine's cooling system. While overheating is rare in winter, it's one of the most common reasons for tow truck calls in summer, especially during long traffic jams at +35°C in direct sun. Here's why it happens, how to catch the problem early, and what to do if the temperature gauge actually climbs into the red.
Why engines overheat in summer
The cooling system is designed to keep the engine at a safe operating temperature under any conditions, but in summer several unfavorable factors hit it at once:
- High ambient temperature reduces radiator efficiency: the temperature difference between the engine and the surrounding air is smaller than in winter, so heat dissipates more slowly;
- Long stretches sitting in traffic mean weak natural airflow through the radiator. While stationary, only the cooling fan does that job;
- Running the A/C adds extra load to the cooling system, since the A/C condenser usually sits in front of the radiator and heats up itself;
- Low or aged coolant. If there isn't enough fluid, or it's lost its properties over time, the cooling system struggles even under normal conditions, and this shows up especially clearly in summer.
Early warning signs of overheating
Overheating rarely happens out of nowhere: there are usually a few signs you can catch ahead of time:
- The temperature gauge slowly but steadily creeps above its usual operating range;
- A hot, slightly sweet smell coming from under the hood. This can indicate evaporating coolant;
- The cabin heater, if switched on, blows noticeably hot air even at the lowest setting. This is sometimes used deliberately as an emergency way to pull some heat off the engine;
- Engine power drops noticeably and the car responds sluggishly to the throttle. Many modern engines enter a protective mode as they approach critical temperature.
What to do in the first seconds after noticing it
- Turn the heater on full blast and open the windows. Counterintuitively, this helps pull some heat off the engine through the heater core, buying you time;
- Pull over to a safe spot as quickly as possible, don't wait until it's completely critical;
- Turn off the engine, but not immediately. Let it idle for 30 to 60 seconds after stopping, if it's safe to do so, to avoid a sudden temperature spike from the coolant that's still circulating;
- Pop the hood (carefully, avoiding hot parts) to help heat dissipate faster.
What you absolutely should not do
- Don't keep driving if the gauge is in the red. Even a few minutes in that state can warp the cylinder head;
- Don't pour cold water on a hot engine or radiator from the outside. The sudden temperature swing can crack the engine block or cylinder head;
- Don't open the cooling system until the engine has fully cooled down. This can take 20 to 30 minutes or more.
What to do once the engine has cooled down
- Check the coolant level in the reservoir only once the system is completely cool;
- Inspect visible hoses and the radiator for leaks, cracks, or signs of steam;
- If the fluid level is normal and the cause isn't obvious, don't risk driving further on your own, especially on a highway or a long trip;
- If fluid is noticeably low or there's a visible leak, continuing to drive before the cause is fixed can lead to far more serious engine damage.
If the cause of the overheating isn't clear or the damage looks serious, it's safer not to gamble with the engine. call a tow truck to the nearest repair shop instead. Fixing a cooling system issue is far cheaper than rebuilding an engine after a serious overheat.
How to reduce the risk of overheating in summer
- Check your coolant condition and level before the hot season starts;
- Make sure the cooling fan turns on properly when the engine heats up;
- Check the radiator for external debris: pollen, dust, and insects can clog the radiator fins and reduce cooling efficiency;
- During long stretches in heavy traffic in extreme heat, periodically turn on the cabin heater. This takes some of the load off the cooling system at a critical moment.
Bottom line
Summer engine overheating is preventable in most cases if you keep an eye on your cooling system and react to the early warning signs instead of waiting for a critical situation. But if overheating does happen and you're not sure how bad the damage is, don't risk continuing to drive. Call a tow truck and get it checked out at a shop instead.
Frequently Asked Questions
Can I top up the cooling system with plain water instead of coolant in an emergency?
As a last resort, to reach the nearest shop, yes, but you should replace it with proper coolant as soon as possible. Plain water doesn't provide the same corrosion protection and has a different boiling point.
How long does an engine need to cool down after overheating?
Usually 20–30 minutes under normal conditions, but the exact time depends on how severe the overheating was and the outside temperature. Only open the cooling system once the upper radiator hose feels warm rather than hot to the touch.
Is it dangerous to let the engine overheat once if I stop right away?
A single brief overheating event with a quick response usually doesn't cause serious damage, but you should have the cooling system checked afterward to identify the cause and prevent it from happening again.
Why does the temperature gauge jump up and down?
This is a common sign of air trapped in the cooling system or a faulty thermostat. It needs to be diagnosed at a shop, and you shouldn't keep driving like that for long.
Does running the A/C contribute to overheating?
A running A/C does add extra load to the cooling system, especially in heavy traffic in the heat, but in a healthy system this shouldn't cause overheating on its own. If it does, there's likely an underlying cooling issue.
Can I still call a tow truck if the engine overheated but then cooled down and started again?
Yes, and that's a sensible choice if you're unsure of the cause. It's better to get the car checked on a flatbed than risk a second, potentially worse overheat on the road.