If your engine is overheating, turn off the AC, turn the heater on full to pull heat away from the engine, and pull over as soon as it's safe. Shut the engine off and don't open the radiator cap while it's hot. The most common causes are coolant leaks, a stuck thermostat, a cooling fan that isn't working and a failing water pump.
What to do the moment it overheats
- Turn off the AC. It adds heat and load.
- Turn the heater on full, fan on high. It feels terrible in July, but the heater core works like a second radiator.
- Pull over as soon as it's safe and shut the engine off.
- Do not open the radiator cap or coolant reservoir while it's hot. The system is pressurized, and coolant can spray out scalding hot.
- Let it cool at least 30 minutes before checking anything.
- Don't keep driving it hot. Overheating can warp the cylinder head or blow the head gasket. That's when a modest repair turns into a major one.
The most common causes
| Cause | Clues |
|---|---|
| Coolant leak: hose, radiator, water pump, heater core | Low coolant, puddles, sweet smell, white residue |
| Stuck-closed thermostat | Overheats quickly, upper radiator hose hot, lower hose cool |
| Cooling fan not running | Overheats in traffic or at idle, fine on the highway |
| Failing water pump | Leak at the pump, bearing noise, overheating under load |
| Clogged radiator | Gradual overheating, especially when towing or in heat |
| Head gasket leak | Bubbles in the reservoir, white exhaust smoke, coolant loss with no leak |
| Broken serpentine belt (on belt-driven pumps) | Sudden overheating plus battery light or no power steering |
Signs of a coolant leak
- Sweet, syrupy smell from the engine bay or vents
- Green, orange, pink or blue puddles under the front of the vehicle
- Low reservoir level that keeps dropping
- Fogging windows with a sweet smell, which can mean a heater core leak
- Dried crusty residue on hoses or the radiator
Why it happens more in the Midlands
Ninety-plus-degree days, stop-and-go traffic, AC running nonstop and towing to the lake all push cooling systems to their limit. Weak parts that get by in mild weather tend to fail in July.
How we diagnose it
- Pressure-test the cooling system to find leaks
- Check fan operation and fan controls
- Test the thermostat and look at the coolant temperature data
- Check for combustion gases in the coolant (head gasket test)
- Inspect the water pump, hoses and radiator
Frequently asked questions
Can I just add water if I'm overheating?
In an emergency, once the engine is cool, water can get you a short distance. Have the system properly filled with the correct coolant mix soon after.
Is it safe to drive if the gauge is a little above normal?
Watch it closely and get it checked. Rising temperatures usually mean something is starting to fail.
Why does my car overheat only in traffic?
That classic sign points to the cooling fan or its controls, since there's no airflow from driving to help.
Do you come to me if my car is overheating?
Yes. Call or text us, and don't drive it. Many cooling repairs are done right where the vehicle is parked.
Want a mechanic to confirm it?
We come to you in Lexington, Irmo, Chapin, Cayce, West Columbia and Columbia, and we test before we replace anything.
