Overheating is one of the few car problems you genuinely cannot drive through. Coolant temperature climbing into the red can turn a modest repair into a blown head gasket — or a destroyed engine — in a matter of minutes. Here’s why cars overheat, what to do the instant it happens, and when to stop.
Why is my car overheating? Common causes
Low coolant or a coolant leak
The most common cause, by far. If coolant is low — usually because it’s leaking from a hose, the radiator, the water pump, or a gasket — there isn’t enough fluid to carry heat away from the engine. Find the leak, fix it, refill, and the problem often goes with it. Old, neglected coolant is a factor too, which is why a periodic coolant flush is cheap insurance.
A stuck thermostat
The thermostat opens to let coolant flow to the radiator once the engine warms up. If it sticks closed, coolant can’t circulate properly and the engine overheats — even with plenty of coolant in the system. It’s a relatively small, common part.
A failing water pump
The water pump circulates coolant through the engine. When it fails — worn bearing, leaking seal, broken impeller — circulation drops and temperatures climb. Often accompanied by a leak or a whine; see water pump replacement cost for what that job runs.
A clogged or damaged radiator
The radiator sheds heat from the coolant. If it’s clogged internally, blocked by debris, or damaged, it can’t cool effectively. A bad radiator cap can cause overheating too.
A bad radiator fan
At low speeds and idle, the cooling fan pulls air through the radiator. If the fan (or its motor/relay) fails, you’ll often see overheating in traffic or at stops, but not at highway speed where airflow is natural.
A blown head gasket (the serious one)
This is the one everyone fears — and ironically, it’s often caused by ignoring the smaller issues above. A blown head gasket can both cause and result from overheating, and it’s a major repair. All the more reason to address overheating immediately.
Gauge climbing or steam under the hood? Call or text Big Tee at (770) 780-0730 — don't risk the engine. We'll find the cause.
What to do when your car overheats
- Turn off the AC and turn the heater to full — it literally pulls heat off the engine and into the cabin (uncomfortable, but it helps).
- Pull over safely as soon as you can and shut the engine off to let it cool.
- Do not open the radiator cap while the engine is hot — pressurized coolant can cause serious burns.
- Once cool, check the coolant level if you can — but the real fix is finding why it overheated.
Can you drive an overheating car?
No. Driving on an overheating engine is how a cooling problem becomes an engine-replacement bill. If the gauge is in the red or you see steam, stop as soon as it’s safe. A short coast to a safe spot is fine; continuing your trip is not.
The fix: diagnose the cooling system, don’t guess
Overheating has many possible causes, and the cheap ones look the same as the expensive ones from the driver’s seat. A proper diagnosis of the cooling system finds the actual cause — coolant leak, thermostat, water pump, radiator, or fan — before you spend. Big Tee handles cooling-system and engine repair for Decatur and Metro Atlanta, with a written quote before any work.
Written by the Big Tee Auto Repair team — 29 years of mobile and shop mechanic experience in Decatur, GA and Metro Atlanta.