# Engine temperature light on? What it means and what to do **Verdict:** Stop driving - **Colour:** Red - **Urgency:** Stop now - **Most common cause:** Low coolant from a leak - **Can I reset it?:** Yes, once fixed ## Quick answer A red coolant temperature light means the engine is overheating or about to. The most common cause is low coolant from a leak, followed by a stuck thermostat, a failed radiator fan, and a worn water pump. Pull over and shut the engine off as soon as it is safe, because continued driving can warp the cylinder head and destroy the engine. ## What does the coolant temperature warning light mean? The coolant temperature light watches how hot the engine is running. A coolant temperature sensor, usually near the thermostat housing, reports the temperature of the coolant flowing through the engine. A water pump circulates that coolant, a thermostat holds it at operating temperature, and the radiator and its electric or belt-driven fan release the extra heat into the air. If any part of that loop fails, heat builds up quickly. The engine computer or gauge cluster switches the red light on when coolant temperature rises above a set limit that is well above normal running temperature. By the time it lights, the engine is already overheating, not just warm. On some cars the same symbol in blue means the engine is still cold, and an amber version can mean the coolant level is low. A red light means pull over as soon as it is safe and shut the engine off. ## What does the coolant temperature warning light look like? A thermometer dipping into wavy lines of liquid. Red means overheating; some cars show it in blue when the engine is still cold, and some use an amber version for low coolant level. | If the light is... | It means | | --- | --- | | Steady | The engine is too hot. Turn off the AC, turn the heater to full hot, pull over and shut the engine off. | | Flashing | On some cars a flashing temperature light is an early warning that temperature is climbing; treat it as a reason to stop soon. | ## Why is the coolant temperature warning light on? 1. **Low coolant from a leak** (most common). Rubber hoses harden and crack with age, radiators corrode or split at their plastic tanks, and water pump seals wear, letting coolant escape until the engine cannot shed heat. Look for green, orange or pink puddles, crusty residue on hoses, or a sweet smell. Small leaks that only seep when hot are easy to miss until the light comes on. 2. **Thermostat stuck closed** (common). The thermostat is a valve that stays shut while the engine warms up, then opens to send coolant to the radiator. If it sticks closed, coolant cannot reach the radiator and the temperature climbs fast, often within minutes of starting. An upper radiator hose that stays cool while the engine overheats points to this. Replacement is usually a modest repair. 3. **Radiator fan not working** (common). At highway speed, air rushing through the grille cools the radiator, but in traffic or at idle the fan must do it. A failed fan motor, relay, fuse or temperature switch lets the engine overheat when stopped while it stays fine on the open road. Overheating that gets worse with the AC on is another common clue. 4. **Failing water pump or broken belt** (less common). The water pump pushes coolant through the engine and is driven by the serpentine belt, the timing belt or an electric motor. A worn bearing, a broken impeller or a leaking seal stops circulation, often with a drip or a grinding noise at the front of the engine. A broken serpentine belt usually turns on the battery light too. 5. **Head gasket failure** (less common). The head gasket seals the joint between the cylinder head and the engine block. When it fails, often after an earlier overheat, hot combustion gas is forced into the coolant, causing repeated overheating, sweet-smelling white exhaust smoke, bubbles in the reservoir and coolant loss with no visible leak. Milky oil can also appear. It is a costly repair. ## What to do right now 1. Turn off the AC and turn the heater and fan to full hot to pull some heat from the engine. 2. Pull over as soon as it is safe and shut the engine off. 3. Wait at least 30 minutes for the engine to cool. Never open the radiator cap or coolant reservoir cap on a hot engine; hot coolant can spray and burn you. 4. Once cool, check the coolant reservoir level and look for leaks or a missing belt. 5. If the coolant is low and you have coolant (or water in an emergency), add it to the reservoir and drive only a short distance to a shop while watching the gauge. Otherwise call for a tow. ## How do you reset the coolant temperature warning light? The light turns off by itself once the engine cools to a normal temperature. If it comes back on, the cause has not been fixed. ## Is it safe to drive with the coolant temperature warning light on? > **Stop driving.** No. Stop driving as soon as it is safe and shut the engine off. Driving an overheating engine even a few miles can cause damage that costs thousands of dollars to repair. ## What to tell your mechanic Tell the shop how far you drove after the light came on, whether you saw steam, smelled sweet coolant or saw white exhaust smoke, and whether it happens in traffic or on the highway. Mention any coolant you added. They will usually pressure test the cooling system, check the fan and thermostat, and test for exhaust gases in the coolant if a head gasket is suspected. ## How to keep the coolant temperature warning light off - Check the coolant reservoir level monthly with the engine cold, keeping it between the min and max marks. - Use the coolant type named in your owner's manual and replace it at the stated interval. - Have hoses, the radiator cap and the water pump checked for leaks or seepage at each service. - Watch the temperature gauge in traffic; a needle that creeps up at idle can mean a failing fan. - Replace a cracked or squealing belt, and the water pump too when a timing belt that drives it is changed. ## Coolant temperature warning light by model Owner complaints to NHTSA that mention this light, by model. Each page shows complaints by model year and related recalls. - [Ford Escape](/warning-lights/coolant-temperature/ford-escape): 1520 complaints - [Ford Edge](/warning-lights/coolant-temperature/ford-edge): 752 complaints - [Ford Explorer](/warning-lights/coolant-temperature/ford-explorer): 222 complaints - [Honda Accord](/warning-lights/coolant-temperature/honda-accord): 193 complaints - [Jeep Wrangler](/warning-lights/coolant-temperature/jeep-wrangler): 143 complaints - [Nissan Rogue](/warning-lights/coolant-temperature/nissan-rogue): 140 complaints - [Chrysler Pacifica](/warning-lights/coolant-temperature/chrysler-pacifica): 139 complaints - [Kia Sorento](/warning-lights/coolant-temperature/kia-sorento): 138 complaints - [Jeep Compass](/warning-lights/coolant-temperature/jeep-compass): 112 complaints - [Kia Soul](/warning-lights/coolant-temperature/kia-soul): 110 complaints - [Chevrolet Silverado](/warning-lights/coolant-temperature/chevrolet-silverado): 100 complaints - [Toyota RAV4](/warning-lights/coolant-temperature/toyota-rav4): 92 complaints - [Honda CR-V](/warning-lights/coolant-temperature/honda-cr-v): 91 complaints - [Jeep Grand Cherokee](/warning-lights/coolant-temperature/jeep-grand-cherokee): 88 complaints - [Ram 1500](/warning-lights/coolant-temperature/ram-1500): 79 complaints - [Hyundai Sonata](/warning-lights/coolant-temperature/hyundai-sonata): 76 complaints - [Jeep Cherokee](/warning-lights/coolant-temperature/jeep-cherokee): 75 complaints - [Hyundai Tucson](/warning-lights/coolant-temperature/hyundai-tucson): 66 complaints - [Ford Mustang](/warning-lights/coolant-temperature/ford-mustang): 64 complaints - [GMC Sierra](/warning-lights/coolant-temperature/gmc-sierra): 58 complaints - [Mazda CX-5](/warning-lights/coolant-temperature/mazda-cx-5): 51 complaints - [Ford Expedition](/warning-lights/coolant-temperature/ford-expedition): 50 complaints - [Honda Pilot](/warning-lights/coolant-temperature/honda-pilot): 46 complaints - [Hyundai Santa Fe](/warning-lights/coolant-temperature/hyundai-santa-fe): 43 complaints - [Honda Odyssey](/warning-lights/coolant-temperature/honda-odyssey): 42 complaints - [Toyota Corolla](/warning-lights/coolant-temperature/toyota-corolla): 41 complaints - [Ford Bronco Sport](/warning-lights/coolant-temperature/ford-bronco-sport): 40 complaints - [Chevrolet Colorado](/warning-lights/coolant-temperature/chevrolet-colorado): 39 complaints - [Subaru Forester](/warning-lights/coolant-temperature/subaru-forester): 38 complaints - [Kia K5](/warning-lights/coolant-temperature/kia-k5): 36 complaints - [Chevrolet Trax](/warning-lights/coolant-temperature/chevrolet-trax): 34 complaints - [Nissan Pathfinder](/warning-lights/coolant-temperature/nissan-pathfinder): 29 complaints - [Toyota Camry](/warning-lights/coolant-temperature/toyota-camry): 29 complaints - [Kia Telluride](/warning-lights/coolant-temperature/kia-telluride): 27 complaints - [Hyundai Elantra](/warning-lights/coolant-temperature/hyundai-elantra): 26 complaints - [Dodge Durango](/warning-lights/coolant-temperature/dodge-durango): 25 complaints - [Subaru Outback](/warning-lights/coolant-temperature/subaru-outback): 25 complaints - [Kia Sportage](/warning-lights/coolant-temperature/kia-sportage): 22 complaints - [Toyota Prius](/warning-lights/coolant-temperature/toyota-prius): 22 complaints - [Volkswagen Jetta](/warning-lights/coolant-temperature/volkswagen-jetta): 22 complaints - [Chevrolet Equinox](/warning-lights/coolant-temperature/chevrolet-equinox): 21 complaints - [Chevrolet Tahoe](/warning-lights/coolant-temperature/chevrolet-tahoe): 21 complaints - [Chevrolet Traverse](/warning-lights/coolant-temperature/chevrolet-traverse): 21 complaints - [Nissan Altima](/warning-lights/coolant-temperature/nissan-altima): 21 complaints - [Kia Forte](/warning-lights/coolant-temperature/kia-forte): 19 complaints - [Toyota Tacoma](/warning-lights/coolant-temperature/toyota-tacoma): 19 complaints - [Honda Civic](/warning-lights/coolant-temperature/honda-civic): 18 complaints - [Tesla Model 3](/warning-lights/coolant-temperature/tesla-model-3): 15 complaints - [Chevrolet Malibu](/warning-lights/coolant-temperature/chevrolet-malibu): 14 complaints - [Toyota Highlander](/warning-lights/coolant-temperature/toyota-highlander): 13 complaints - [Toyota Tundra](/warning-lights/coolant-temperature/toyota-tundra): 13 complaints - [Dodge Charger](/warning-lights/coolant-temperature/dodge-charger): 12 complaints - [Honda HR-V](/warning-lights/coolant-temperature/honda-hr-v): 11 complaints - [Volkswagen Tiguan](/warning-lights/coolant-temperature/volkswagen-tiguan): 11 complaints - [Mazda 3](/warning-lights/coolant-temperature/mazda-3): 6 complaints - [Subaru Crosstrek](/warning-lights/coolant-temperature/subaru-crosstrek): 6 complaints - [Ford Ranger](/warning-lights/coolant-temperature/ford-ranger): 5 complaints - [Ford F-150](/warning-lights/coolant-temperature/ford-f-150): 4 complaints ## Trouble codes behind this light - [P0217](/codes/p0217): Engine Coolant Over Temperature Condition ## Frequently asked questions ### Can I drive with the coolant temperature light on? No, you should pull over and shut the engine off as soon as it is safe. An overheating engine can warp the cylinder head or blow the head gasket within minutes. Let it cool for at least 30 minutes before checking anything, and call for a tow if you cannot find the cause. ### What does a blue temperature light mean? It means the engine is still cold, and it turns off once the engine warms up. It is not a warning of a problem. Drive gently and avoid high engine speeds until it goes out. If it never goes out, the thermostat may be stuck open or the sensor may be faulty. ### Why does the temperature light come on and then go off? Usually because coolant is low or the radiator fan is cutting in late, so the temperature spikes and then recovers. It is an early warning, not a false alarm. Check the coolant level when the engine is cold, look for leaks, and have the cooling system inspected before it gets worse. ### How long can I drive with the engine overheating? As little as possible, ideally not at all once the red light is on. Every extra mile raises the risk of a warped head, a blown head gasket or seized pistons. Pull over at the first safe spot, shut the engine off, and let it cool before deciding what to do next. ### Can I add water instead of coolant? In an emergency, yes, plain water added to the reservoir of a cooled engine can get you a short distance to a shop. It does not protect against freezing or corrosion, so have the system drained and refilled with the correct coolant soon. Never open the cap on a hot engine. ### Why is my car overheating when the coolant is full? Usually because coolant is not moving or not losing heat. A thermostat stuck closed, a failed radiator fan, a worn water pump or a clogged radiator are the common reasons, and a failing head gasket can also do it. A shop can pressure test the system and check each part. ### How much does it cost to fix an overheating engine? It depends on the cause. A thermostat is often about 150 to 450 dollars, a water pump or radiator usually 400 to 1,200 dollars, and a head gasket repair often well over 1,500 dollars at an independent shop in 2026. Stopping the engine early keeps the bill at the low end. ### Is it safe to open the radiator cap when the engine is hot? No. The cooling system is under pressure, and opening the cap on a hot engine can spray scalding coolant and steam onto your face and arms. Wait at least 30 minutes, until the upper hose is cool to the touch, then open the cap slowly with a thick rag over it. ### Why does my car overheat only in traffic? Most often because the radiator fan is not working. At speed, air through the grille cools the radiator, but at a stop the fan has to pull air through. A failed fan motor, relay, fuse or switch is typical, and low coolant makes it worse. Have the fan circuit tested. ### Should I turn on the heater when my engine overheats? Yes, turning the heater and fan to full hot and switching off the AC moves some engine heat into the cabin. It can slow the temperature rise for the minute or two it takes to find a safe place to stop. It is not a fix, so still pull over and shut the engine off. ## Sources - [Car Care Council: Car care guide](https://www.carcare.org/car-care-guide/) - [AAA: Approved Auto Repair](https://www.aaa.com/autorepair/) ## Other warning lights - [ABS warning light](https://diagxcar.com/warning-lights/abs) - [Airbag (SRS) warning light](https://diagxcar.com/warning-lights/airbag) - [Battery (charging system) warning light](https://diagxcar.com/warning-lights/battery) - [Brake warning light](https://diagxcar.com/warning-lights/brake) - [Check engine light](https://diagxcar.com/warning-lights/check-engine) - [Oil pressure warning light](https://diagxcar.com/warning-lights/oil-pressure) - [Power steering warning light](https://diagxcar.com/warning-lights/power-steering) - [Tire pressure (TPMS) light](https://diagxcar.com/warning-lights/tire-pressure) - [Traction control light](https://diagxcar.com/warning-lights/traction-control) ## Symptoms - [Why is my car overheating?](https://diagxcar.com/symptoms/car-overheating) - [Why is white smoke coming from my exhaust?](https://diagxcar.com/symptoms/white-smoke-from-exhaust) ## Repair costs - [Thermostat replacement cost](https://diagxcar.com/cost/thermostat-replacement): $150-$450 - [Water pump replacement cost](https://diagxcar.com/cost/water-pump-replacement): $400-$1,200 - [Radiator replacement cost](https://diagxcar.com/cost/radiator-replacement): $500-$1,200 - [Serpentine belt replacement cost](https://diagxcar.com/cost/serpentine-belt-replacement): $100-$250 ## Terms explained - [What is Coolant?](https://diagxcar.com/glossary/coolant) --- Source page: https://diagxcar.com/warning-lights/coolant-temperature Updated: 2026-11-03 General information, not a substitute for a qualified mechanic.