So ever since I bought my 8 6 months ago the red coolant / radiator light has always been on. The previous owner said that it had always been on but never had any problems. My rx8 is a 2004 automatic at 108,000 miles if that matters. Is there something wrong and what can I do to get rid of the light?

 

Common failure. The coolant level sensor in the coolant bottle is water logged and can not float any more. You can either unplug the sensor with the knowledge that you must watch your coolant like a hawk, especially with old cooling components in the car, or you can replace the coolant bottle (The sensor is formed into the bottle) for $130 and a fairly easy labor. Just be wary of the small hose that leads to the top of the radiator from the bottom of the bottle. If your radiator is more than 20,000 or so miles old, the hose will be stronger than the nipple it attaches to, and it will break the radiator nipple off, and you will have to replace the radiator too. That is a very common mistake made.

If you opt to replace the coolant bottle, at your mileage, I would recommend taking a weekend and replace the radiator, thermostat, and coolant lines while you are at it. Very similar work requirements, ~$500 in parts, and it will ensure you don't lose your engine from overheating when a high mileage part fails. That type of engine failure is also very common.

 

Just a curious question, My 06 Shinka (80,000 miles, 15,000 on current engine) has been acting weird along these lines over the past few weeks. I will be driving around town like normal and the radiator light will come on and I always pull over right away for fear of messing up the engine, and upon inspection the coolant levels are always fine and the temperature indicator inside the car is showing a normal temperature.

I have read a few threads on here saying that the sensor is going bad, which I think is a possibility. Mine if more random though and there is no particular event or "thing" that I do that can get the light to come on. After turning the car off on the side of the road and then turning it back on, the light is off and it stays off.

JW, any second opinions would be nice.

 

It's either a sensor problem or you are starting to have a cooling system failure. Pop the hood and have sometime raise the RPMs up to 6-7k while you watch the coolant level. If the coolant level drops sharply or there is a mass of bubbles, then you have something failing in your cooling system. If the coolant level only dips a bit, or doesn't dip at all, it's just the sensor.

If your engine is a Mazda reman and you haven't flushed the cooling system and/or replaced the radiator and thermostat, then you should do that. Lots of cooling system failures from clogs after a Mazda reman is installed, thanks to the excess sealant that they use that breaks off and floats around in the coolant until it clogs something.

 

I can now confirm that there is a problem with my sensor in my coolant reservoir. I was driving around like normal and then did my daily redline after I have just put a little more coolant in. I should note that my daily redline's are just a quick bump to 9.5k RPM in second gear and then back down and over to 6th gear. Seconds after I popped over to 6th gear on the highway the coolant light came on again. Engine temps were fine and I drove home to check things out and there was nothing wrong with coolant levels or any components related that I could see. I really feel like that damn sensor did go bad now because I went out to meet someone for dinner two hours later and when I started her up the light was off and has been off since.

Thanks for the info, Ordered a new reservoir and it is on its way.

 

Don't forget about that little hose to the radiator...

 

I was having the same problem... but it was actually a small crack in the rad (after two Mazda remans.) I replaced the radiator and now everything is fine. Make sure to check the rad for any small cracks.

 

how about 'just a couple bubbles; maybe six while holding at about 6K rpms?'

 

that's within acceptable normals, as long as it isn't a steady stream of them. If it's just a few bubbles that pop up, then stop, nothing to worry about.