Why does my low coolant light keep coming on?

The low coolant warning light is coming on in my Mazda RX-8 when driving over 120km/h. Coolant level and oil are ok. Any idea what's causing this? The light goes off again after a few minutes.

Sean Naughton (Co. Limerick)

Oct 2011 Filed under: fault

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Expert answer

Hi Sean,

This is a well known issue with the Mazda RX-8. The level sensor in the overflow bottle starts to go. Check the coolant level when the car is stone cold and if it's down then top it up. Some people find that sorts out the light. If not, you could try to clean the sensor, but this might not do anything. I believe it's integral to the tank so you'd have to take it all out.

Because it's integral to the tank it'll be pricey to replace. Don't use a second-hand one, as they tend to go after a while regardless.

You can stop the light coming on by disconnecting the wiring to the sensor. Most people don't have a coolant level light anyway so just keep an eye on the level for yourself.

Hope that helps

Shane O' Donoghue - Complete Car Adviser
@Shane_O_D