I've had this problem with my engine coolant light for quite sometime. I don't know if it's serious or if my sensor is failing. When I first got it, I thought it was low and so with the help of my dad, we replaced the engine coolant. After a week or two, the light kept appearing even though there was plenty of new coolant. Sometimes it goes away as I drive and other times it just stays on. I don't if somethings wrong, I've checked so many times but everything is fine, I'm somewhat worried.

 

It's a common problem, the sensor is bad. You have to replace the whole tank.

 

We see it all the time, replace the tank.

 

By tank you mean the coolant reservoir? Like this https://www.amazon.com/dp/B0091U3CBO...awd_8Ezdvb1PX?

 

Yes

 

There is a sensor-less version of the tank, and that listing looks like it's the one.

See this: MAZMART - Serving The Mazda Community Since 1980. RX8 Coolant Tank (2004-11)

Scroll down, and you can see the different versions of the tank. The ones with the level sensor has the connector hanging off the left side. Doesn't make too much sense to buy a replacement tank without a sensor if you are trying to fix the sensor. The cheaper option in that case would be to just unplug it.

 

Amazon picture shows the sensor installed and all the reviewers say it comes with the sensor. The parts number is also for the complete assembly N3H1-15-351G