My car is overheating. What should I do?
Short answer
Pull over as soon as it's safe, turn off the air conditioning, and if you see steam or leaking coolant or the gauge is in the red, shut the engine off and let it cool for at least 30 minutes before touching anything. Never open the radiator or coolant cap while the engine is hot, and don't keep driving an overheating engine; the usual causes are low coolant from a leak, a stuck thermostat, a cooling fan that isn't running, a bad belt or water pump, or a clogged radiator.
Safety first. Never remove the radiator cap or coolant reservoir cap on a hot engine: hot coolant and steam can spray out under pressure and cause serious burns. Don't open the hood while steam is coming out, and keep hands, hair and clothing away from the cooling fan and belts, which can start moving on their own. Nissan's owner's manuals warn that driving on with an overheating engine can even cause a fire.
On this page
Step by step
- 1
Pull over safely
Get off the road with your hazard lights on, shift into Park and set the parking brake. Get passengers out and away from traffic if you're on a busy shoulder.
- 2
Turn off the A/C (and turn the heat up if you can't stop yet)
The air conditioning adds load to a hot engine. If you can't pull over right away, AAA says turning the heater to hot with the fan on high pulls some heat out of the engine. It only buys you a little time.
- 3
Look for steam or leaking coolant
If steam is coming from under the hood or coolant is running out underneath, shut the engine off and stay back. Don't open the hood until the steam stops.
- 4
Decide whether to shut it off
Hyundai's and Nissan's owner's manuals say that if there's no steam and no leak, you can leave the engine idling and check that the radiator fan is spinning; if the fan isn't running, shut the engine off. If you're not sure, or the gauge stays in the red, shut it off. AAA's advice is simply to turn it off and call for a tow.
- 5
Let it cool before you touch anything
Give it at least 30 minutes. Then check the coolant level at the see-through reservoir, not by opening the radiator cap. Look for wet hoses, drips under the car and a loose or broken belt.
- 6
Add coolant slowly, only once it's cool
If the reservoir is low, add the coolant your owner's manual calls for, a little at a time. Hyundai warns that suddenly pouring coolant into an engine that overheated from low coolant can crack the engine. Never splash cold water on a hot engine.
- 7
Get it checked, or call a tow
Low coolant means a leak somewhere, because the system is sealed. If it overheats again, the coolant was gone, the belt is broken or the fan doesn't run, have it towed rather than driven.
How to tell your engine is overheating
- The temperature gauge climbs toward H or into the red, or a red temperature warning light comes on. Normal is usually around the middle.
- Steam from under the hood. Coolant leaking onto hot parts boils off as steam.
- A sweet smell, which is burning coolant, or a hot, burning-plastic smell. See Why does my car smell sweet?
- Coolant on the ground, often bright green, orange, pink, blue or yellow.
- Less power. AAA says you may need more gas than usual to accelerate.
AAA points out that the gauge depends on the thermostat and sensor working, so a strange smell or steam with a normal-looking gauge still deserves a look.
Why cars overheat
| Cause | Clues | Usual fix |
|---|---|---|
| Low coolant from a leak | Reservoir below the line, puddles, wet hoses, sweet smell | Find and fix the leak (hose, radiator, water pump, cap), then refill |
| Stuck thermostat | Gauge swings up and down, or climbs with no leak | Replace the thermostat |
| Cooling fan not running | Overheats in traffic or at idle, fine at highway speed | Fan motor, relay, fuse or sensor repair |
| Broken or loose serpentine belt | Squeal, battery light, heavy steering along with overheating | Replace the belt (and check what it drives) |
| Failing water pump | Coolant drip at the front of the engine, steam from the radiator | Replace the pump; AAA says most last 60,000 to 100,000 miles |
| Clogged or damaged radiator, bad cap | Debris on the radiator fins, a rusty radiator, a cracked cap | Clean or replace radiator, replace cap, flush coolant |
| Leaking head gasket | Sweet white exhaust smoke, coolant loss with no visible leak, milky oil, bubbles in the reservoir | Shop test, then head gasket repair |
| Low engine oil | Oil below the dipstick mark | Top up and find out why it’s low |
Sources: AAA, Farmers, Tires Plus, CRC Industries.
Why the belt and the battery light matter together
On many engines one belt drives the alternator and the water pump. If the battery light comes on and then the temperature gauge starts to rise, the belt has probably broken: the water pump has stopped moving coolant. Stop and call a tow. See Why is my battery light on while driving?
What not to do
- Don’t open the radiator cap hot. The system is under pressure; wait until it’s cool, then open it slowly with a thick rag, per Hyundai’s manual. Better: check the reservoir instead.
- Don’t pour cold water on the engine. Farmers warns of thermal shock to hot metal.
- Don’t keep topping it up and driving. Coolant doesn’t disappear on its own. AAA calls adding coolant and continuing to drive dangerous; it only hides a leak until the next overheat.
When to see a pro
Call a tow if coolant was pouring out, the belt is broken, the fan doesn’t run, there’s white smoke from the exhaust, or it overheats again after cooling down and topping up. Book a shop visit soon if you had to add coolant at all: a pressure test finds leaks, and a cooling-system check covers the thermostat, fan, cap and hoses. Overheating that’s caught early is usually a hose, thermostat or fan; overheating that’s driven on can become a head gasket or a new engine.
Common follow-up questions
Can I keep driving if my car is overheating?
No. Driving with the gauge in the red can warp the cylinder head, blow the head gasket or wreck the engine, and Nissan warns it can even cause a fire. Pull over, let it cool, and only drive on if the cause was simple, the coolant is back to the right level and the gauge stays normal. If it climbs again, stop and call a tow.
Where should the temperature gauge normally sit?
On most cars, around the middle once the engine is warm. AAA's Oregon/Idaho club says the needle should sit mid-range or lower and never reach three-quarters. Some cars use a warning light instead of a gauge. Learn where yours normally sits, because a change from that is the real warning.
Why does turning the heater on help an overheating car?
The heater core is a small radiator inside the dashboard that runs on engine coolant. Heat on full with the fan on high moves some engine heat into the cabin. Nissan's owner's manuals list it as a step while idling, and AAA's Oregon/Idaho club suggests it if you can't pull over right away, but only as a short-term measure.
Can I just add water instead of coolant?
In an emergency, plain water can get you to a shop once the engine has cooled, but it doesn't protect against freezing, boiling or corrosion the way the right coolant does. Get the system drained and refilled with the coolant your owner's manual specifies. AAA notes that coolant mixed incorrectly causes problems too.
My car overheats sitting in traffic but is fine on the highway. Why?
At highway speed, air is pushed through the radiator by the car's own motion. In traffic, the electric cooling fan has to do that job, so a fan that isn't switching on, a bad fan relay or fuse, or a radiator blocked with debris often shows up only when you're stopped. AAA also notes stop-and-go traffic is harder on the engine because it idles more. Check whether the fan runs when the engine is hot.
What does it mean if the car overheats and I see white smoke from the exhaust?
Sweet-smelling white exhaust along with coolant that keeps disappearing can point to a leaking head gasket, which lets coolant into the cylinders. Other signs CRC lists are milky oil on the dipstick and bubbles in the coolant reservoir with the engine running. A shop confirms it with a compression test or a chemical test for exhaust gases in the coolant. Don't keep driving it.
Is a coolant leak under my car the cause?
Very likely, if the reservoir is low. AAA says coolant can be yellow, orange, red, green, blue or violet and smells sweet. Clear water dripping from under the front passenger side after using the A/C is normal condensation, which Hyundai's manual points out.
Sources
- 1.Hyundai Sonata 2025 Owner's Manual: If the engine overheats
- 2.Nissan X-Trail 2024 Owner's Manual: If your vehicle overheats
- 3.AAA: Car Overheating, 8 Causes and Solutions
- 4.AAA Oregon/Idaho: What to do if Your Car is Overheating and How to Prevent it (Jul 2024, updated Jul 2025)
- 5.Farmers Insurance: What to Do If Your Car Engine Overheats
- 6.Tires Plus: Why Is My Car Overheating? (Jun 2018)
- 7.CRC Industries: Spotting Blown Head Gasket Symptoms (Jan 2025, revised May 2026)
General information only, not a diagnosis. Your owner’s manual comes first. How we write these