Why does my car overheat in summer traffic?

Why does overheating happen in traffic but not on the open road?

At low speed the radiator depends on the cooling fan; a failed fan or fan relay often shows up only in traffic. When you drive faster, air passing through the front of the car helps carry heat away from the radiator. In a queue, that airflow falls, so a weak or inactive fan becomes more noticeable. This explains why your temperature gauge might look normal on an open road but rise while you wait at junctions in Tbilisi. The pattern points towards an airflow problem, but it does not identify the faulty part by itself.

A shop should check whether the fan is being commanded to run and whether it actually operates as intended. The fault could involve the motor, relay, wiring, fuse or control system rather than the fan assembly alone. Some cars use different fan speeds or more than one fan, so seeing a fan turn does not prove the system works correctly under load. Tell the technician whether the temperature drops once traffic starts moving, whether the AC was running, and whether the issue happens every trip or only occasionally.

How do coolant and radiator problems contribute?

Low coolant, a clogged radiator or a sticking thermostat also cause overheating. Coolant carries heat away from the engine, while the radiator transfers that heat to the surrounding air. A shortage, restricted flow or poor heat transfer can leave too little cooling capacity for hot, slow traffic. When the engine is completely cold, you can check the reservoir level against the markings and look for visible wet patches or dried residue. A low level is a reason to investigate, not simply a maintenance task to repeat whenever the warning returns.

Radiator problems can involve blocked airflow outside or restricted coolant flow inside, and those need different checks. Debris or damaged fins may reduce airflow, while internal deposits may restrict circulation. A thermostat that does not open correctly can also limit circulation, but you cannot reliably diagnose it from the dashboard gauge alone. For an imported used car with an uncertain maintenance history, ask the shop to assess coolant condition and suitability rather than assume the existing fluid is correct. Use your owner's manual or the shop's guidance for the required coolant specification.

Why does switching on the AC make it worse?

AC use adds load to the cooling system on hot days. The AC system releases heat near the engine's cooling airflow, and operating it also adds work for the engine. A healthy system is designed to manage normal AC operation, so repeated overheating with the AC on deserves investigation rather than permanent avoidance of air conditioning. In slow summer traffic, the combination of hot outside air, limited road airflow and AC operation can expose a fan or radiator problem that is less obvious during cooler weather or steady driving.

The exact fan behaviour depends on your car's design, engine and control strategy, so do not rely on a universal rule about when a fan must start. Tell the shop if the AC becomes less effective while you are stationary, especially if engine temperature rises at the same time. That combination can help guide airflow checks, but it does not prove a specific component has failed. Mountain climbs can add engine load too; overheating there does not automatically mean you have the same fault as a car that overheats only while idling.

What should you do when the temperature rises?

If the temperature climbs, switch the AC off and the heater on and stop safely if it reaches the red zone. The heater can remove some engine heat, but it is a temporary measure while you find a safe place to stop, not a repair. If there is steam, a serious warning or a sudden loss of power, stop as soon as you can do so safely and switch the engine off. Do not keep driving merely because your destination or a repair shop is close; arrange roadside help when continuing would risk further overheating.

Keep clear of escaping steam and never open a hot radiator or pressurised coolant cap. Hot coolant can spray out and cause serious burns. Wait until the engine is fully cold before considering a level check, and follow the owner's manual because access and procedures vary. Do not pour cold water over a hot engine or reach towards a cooling fan, which may start unexpectedly. If you are stopped in an exposed roadside location, prioritise your safety and that of your passengers over inspecting the engine or trying to identify the leak.

• Watch the temperature gauge and any warning message.
• Reduce AC load while finding a safe stopping place.
• Switch off the engine after stopping for serious overheating.
• Leave hot caps closed and stay clear of steam.
• Seek assistance if coolant is escaping or the warning returns.

When should you book a cooling-system check?

Book a cooling-system check if the temperature repeatedly rises in traffic, coolant keeps dropping or you notice a leak, even if the car cools down once moving. Do not wait for another red-zone event to confirm that something is wrong. Useful checks may include fan operation, electrical controls, leaks, radiator condition, coolant circulation and thermostat operation, selected according to the symptoms. If overheating followed recent cooling-system work, tell the shop exactly what was done; incorrect filling or trapped air may need consideration alongside a new component fault.

Bring a clear symptom history rather than requesting a replacement fan or radiator before diagnosis. Note whether the engine was idling, the AC was on, the heater changed temperature or a warning appeared. Mention any LPG/CNG conversion and recent related work so the technician can consider the actual installation, without assuming the conversion caused the fault. On Junto, you can find shops at junto.ge/services by service, price, place and next free time, then request an online booking for the shop to confirm. Suggested extra work can be sent for your approval by SMS link.

Before authorising repairs, ask what test supports the diagnosis and whether the shop has reproduced the traffic-related symptom. Ask how it will verify cooling after the repair, including operation under the conditions that originally caused trouble. You do not need to choose technical parts yourself, but you should understand which fault was found and what work is proposed. With Junto's approval link, you can see each suggested work line and its price before work starts, helping you make a decision without relying only on a hurried phone explanation.

Questions and answers