Blog · Updated September 29, 2026 · 7 min read · By the Miles team
The temp gauge is climbing. Here is what to do.
Almost everything written about overheating is a list of causes. That is the right thing to read tomorrow, sitting at a desk. Stopped on the shoulder with the needle past halfway, what you want to know is how to get the heat out, what you must not touch, and whether the car moves again under its own power.
The first two minutes
Switch the air conditioning off and the cabin heater to maximum, with the fan on high. That sounds backwards and it is the fastest thing you can do from the driver's seat, because the heater core pulls heat out of the coolant into the cabin. Then find somewhere safe to stop and shut the engine off.
While that is happening, note the mileage and when the gauge started to move. A note in Miles keeps both on the vehicle's timeline with a date against it, and a shop will ask you for both.
- Air conditioning off, heater on full. The cabin gets unpleasant, and it moves real heat out of the engine.
- Get out of stop-and-go if you safely can. Many cars shed heat better moving than idling, since airflow does what a struggling fan cannot.
- Pull over and switch off. A stopped engine stops making heat, and nothing else on this list does that.
- Open the hood once the engine is off. Trapped heat escapes faster, and you are not touching anything yet.
Leave it off for half an hour or more before you investigate. There is no way to hurry this part safely.
What not to touch
Do not loosen the radiator cap or the expansion tank cap on a hot engine. The cooling system is pressurized, which holds the coolant liquid above the temperature where it would otherwise boil. Releasing that pressure by hand can put scalding fluid and steam where your arm is.
Do not pour cold water into a hot engine either. Cold water against hot metal can crack a head or a block, turning a cooling fault into an engine replacement. Wait until everything is cool, then top up with the coolant type your owner's manual specifies. Coolant is also toxic if swallowed and tastes sweet to animals, so clean up any puddle you leave on the roadside.
Drive it, or call a tow?
Start from the assumption that it does not get driven. A genuinely overheating engine that keeps running is how a repairable fault turns into a replaced one, so the burden is on the evidence to say it is safe. Three signs settle it outright: the gauge in the red, an overheat or coolant warning, or visible steam.
Any of those means stop and call for a tow. If instead the gauge climbed partway, came back down once the heater was on, and the coolant level looks right when the engine is cold, a short careful drive to a nearby shop is often reasonable, with the gauge watched the whole way. Stop again the moment it climbs. If there is no shop close by, pay for the tow.
It cooled down. Is the engine hurt?
A gauge back at normal tells you the engine shed its heat. It does not tell you the cause went away, and it does not undo what the heat already did. That is why a single overheat is worth taking seriously even when the car drives home fine.
Heat is hard on aluminum. A serious overheat can warp a cylinder head or fail a head gasket, and the symptoms often arrive later as coolant loss with no visible leak, white vapor from the exhaust that does not clear, or the temperature creeping up under load. Damage accumulates across events rather than resetting between them, so the second and third overheat matter more than the first. Have it inspected promptly, and tell the shop how hot it got.
What is usually behind it
Nearly all of it comes down to coolant that is too low, or coolant that is not moving. A low level points at a leak, and no circulation points at a failed part. Telling them apart takes a pressure test, so treat this as a shortlist for understanding the shop rather than a diagnosis.
- Low coolant, from a hose, the radiator, the water pump seal or the expansion tank.
- A cooling fan that is not running, which shows up first in traffic and clears on the open road.
- A thermostat stuck shut, so the coolant never reaches the radiator.
- A failing water pump, which stops the coolant circulating at all.
- A blocked radiator, internally with age, or externally with road debris.
Old coolant contributes to several of these, since the corrosion inhibitors deplete over time. Intervals vary widely by coolant type and vehicle, and your owner's manual is the authority on yours.
Why one overheat is worth writing down
A second overheat means something a first one does not, and you can only see that if the first was written down. One in traffic on a hot afternoon reads as bad luck. The same thing twice in a summer is a fan or a slow leak telling you what it is.
So write down the date, the mileage, how hot it got and what you were doing. Miles keeps each entry with the date, mileage, cost, notes and a photo, and reminds you by time or mileage, whichever comes first. It is free with one vehicle, and the features page shows how the timeline works. Records matter beyond the repair, too. Your warranty rights under federal law do not require dealer servicing, but they do rest on showing the work was done. Cooling fans and water pumps also turn up in safety recalls, so run the VIN through NHTSA's recall lookup, which Miles checks for each vehicle you add.
Frequently asked questions
Can I keep driving if my car is overheating?
Treat the answer as no until something tells you otherwise. Driving an engine that is genuinely overheating is how a repairable fault becomes a replaced engine, and the damage builds with every mile. If the gauge reaches the red, a warning light comes on, or you see steam, stop as soon as it is safe to do so and have the vehicle towed. Heat damage to a cylinder head or a head gasket costs far more than a tow does.
How long should I wait before opening the hood?
You can open the hood once the engine is off, which helps heat escape, but leave the radiator and expansion tank caps alone. A cooling system is pressurized, so a hot cap can release scalding coolant and steam when it is loosened. Give it at least 30 to 45 minutes before you touch a cap, and longer if the gauge was in the red. If you are unsure, wait until it is cold to the touch.
Can I pour water into the radiator to cool it down?
Not while the engine is hot. Cold water meeting hot metal can crack a cylinder head or a block through thermal shock, which turns a cooling fault into a much larger repair. Once the engine is fully cool, plain water will get you to a shop in an emergency, but it dilutes the corrosion protection and the freeze protection, so it is a short term measure only. Have the correct coolant put back in.
The gauge came back to normal. Do I still need it looked at?
Yes. A normal gauge means the engine shed its heat, not that the cause went away, and most causes of overheating get worse rather than better. A low coolant level points to a leak somewhere, and a fan, thermostat or water pump that failed once will fail again, usually in traffic. Have it inspected promptly, and write down the date and mileage so a second event is recognizable as a pattern.