Warning lights
Low coolant warning light on: what to do
The low coolant light means there is less fluid in the expansion tank than there should be. There is almost always a leak or the engine is consuming coolant, and if the level keeps dropping the engine can overheat.
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Reviewed by Daniel Morales, founder of Reprorace SL, on
Is it serious? Can I keep driving?
Carefully, and only as far as the garage. If the engine temperature is normal, you can make a short, gentle trip until you can top it up. If the temperature climbs, the red light comes on or you see steam, stop as soon as it is safe and switch the engine off.
A careful, general answer: only someone who inspects the car can say whether it is safe to drive. When in doubt, stop somewhere safe and call for assistance.
Most likely causes
- Leaking hose or clamp: leaves residue or colored crust around the joint.
- Radiator or expansion tank: a small crack leaks mostly when hot and under pressure.
- Water pump: its seal starts to drip as it wears.
- Tank cap: if it does not seal, coolant escapes as steam.
- Head gasket: less common: the engine burns coolant, usually with white smoke and a sweet smell.
Listed from more to less common in general; on your car they may be different. A fault-code reading and a check at the garage confirm which one it is.
To understand it better: What does the engine thermostat do and what does P0128 mean? What is live data and what is it for?
Car system: Cooling
What you can check yourself
With the engine cold, look at the level in the expansion tank against the MIN and MAX marks.
Never open the cap with the engine hot: the fluid comes out under pressure and burns.
Top up with the coolant the owner's manual specifies; in an emergency use water and have it replaced later.
Look for drips under the car and fluid traces on the hoses, radiator and pump.
Safe checks only: with the engine off and cold whenever you look under the hood, without taking anything apart and without touching hot or moving parts.
Related fault codes
- P2560Engine coolant level: too low
- P2556Engine coolant level sensor/switch, circuit: malfunction
- P0217Engine coolant: over temperature
- P0128Coolant thermostat: coolant temperature below the thermostat regulating temperature
Generic codes that often come with this symptom. Seeing one does not confirm the cause: it is where the diagnosis starts.
How the ECO-LITE helps diagnose it
Plugged into the OBD socket, the ECO-LITE reads the fault codes of the control units that answer, with the freeze-frame data captured when the fault happened, and shows live data on your phone or computer. With your permission, your garage can see them remotely before you bring the car in.
What to look at here: live coolant temperature, how long it takes to warm up and engine level or temperature codes.
Frequently asked questions
Is it normal for coolant to drop a little?
A minimal loss over the years can happen, but if you top up often there is a leak or consumption to check.
Can I mix different coolants?
Better not: some are not compatible. Use the one in the owner's manual or the one already in the car.
What happens if I drive without coolant?
The engine overheats quickly and the head gasket or the cylinder head can be damaged.
Keep reading
- Engine cooling: how it works and what fails
- Engine temperature warning light on: what to do
- Sweet antifreeze smell: what it means and what to do
- White smoke from the exhaust: what it means and what to do
- Car symptoms: what they mean and what to do
- Check engine light on: what to do
- How to read and clear your car's fault codes
- OBD fault codes: what each one means