I recently bought an 05 rx8, when i started driving it up to 115km/hour my coolant light use to come on and I had to slow down in order for the light to come off, so I decided to change my coolant, and now after I changed it the coolant light comes on and won't turn off. Even if I drive slow.. Any thoughts? Thanks

 

It's a faulty sensor. Very common.

You should read the new and potential owners sticky found at the top of the new members forum

 

The coolant light come on because the coolant float and switch are a lousy non dependable design. I got tired of messing with it and because it is an inferior design a new one will probably fail down the road. I do not recommend this but i did connected mine. I am retired and i play with my 8 every day so i am under the hood daily and i am checking fluid levels every day. The coolant light is really an idiot light because after it warns you by comming on it is likely to late and damage is usually already done.

 

^negative. It's the temp gauge you're thinking off.

 

I think it's the senser, but I'm paranoid because it use to come on everytime I reach 120-130 and it goes off when I slow down, but now it come on every time I drive for 10 mins and it won't go off

 

In your case, yes it's quite possibly the sensor, as I already stated is a common issue.
Have you read the new owners thread as I suggested? If it is a faulty sensor, you'll need to replace the whole overfill tank.

 

Mazmart has the OEM coolant bottle with the sensor, no cap for $110, with the cap, $125
That is a cheap price that could save your engine.
If you ignore the coolant light, and you get a leak while driving, you won't know it until it's too late.
Overheating kills rotary engines quickly.
$125 vs. $5000 and being without your car for a few weeks.

Replace your tank, problem solved.
DON'T unplug it!

 

Also, if you DIY, be VERY careful with the hose attached to the plastic radiator nipple.
They are fragile, and many members have accidentally broken them taking the hose off.
Use a utility knife to split the hose lengthwise along the nipple and peel it off, kinda like a banana.
Get a little pack of radiator hose grease from your local parts store to lube the new hose.

 

Your incorrect , it is and was the temp float and switch that is the issue.The idiot light only tells you when it's too late. That's why it's called an idiot light. If the float and switch were not inferior it would be a different story , But the idiot light would still serve to be too late. A after market accurate temp gauge is what i am installing afte xmas is over.

 

Temp float switch?

The low coolant lights comes on when either the coolant is low or the level switch in the coolant reservoir is going bad. As stated before, either replace it with a new reservoir (you can get it with or without the level sensor) or just unplug it. The low level sensor is okay to have but since you should be checking the oil level often then checking the coolant level should not be a huge inconvenience.

 

I usually don't disagree with you because your knowledge of the 8 is vastly superior to mine, but I don't think unplugging the light is a good idea.
Iirc, I think you have the real temperature gauges with audible warning?
I think most owners don't.

If someone develops a leak while driving, (like catching a rock or some debris in the radiator, or a hose started leaking) and begins to lose coolant, I would think the coolant light would come on before the engine started to overheat.
Would you agree?
If the light was disabled, and coolant loss led to the engine overheating, by the time the driver noticed the temp gauge rising, the engine could already be damaged.

 

don't be cheap or it'll get expensive. $125 is a small price to pay.

 

I don't have an aftermarket coolant temp gauge. I mean the light helps but they don't have them in every car, so I don't think it's a big deal. I have aftermarket reservoirs with a visual level so I just check them anytime I have the hood open, no big deal.

That said, when my car was stock and the level sensor went out I installed a new reservoir with a sensor because I like things to work and $125.00 is nothing in the world of rotary ownership.

 

I must be thinking of someone else with the gauge.
Yeah, $125 is a drop in the RX8 bucket.

 

Actualyy it's a general bug for Series 1 cars. The sensor'a are bugged. If your car temperature is just fine there is nothing to be affraid off.

I just took my sensor off =)

 

That's bad advice.
You don't know what you're talking about.

If your coolant system develops a leak while you're driving, your temperature gauge won't start moving until it's already overheating, and unless you pay close attention to your gauge, your engine will likely be damaged before you even notice it.

I really don't understand the mindset of disabling a warning light because it's somehow inconvenient to fix it.

 

Me either, my 2008 had the same issue, float went bad or whatever, light would come on from time to time stay on ~30 seconds then go off. Really not that hard to replace it, remove some plastic in the engine bay, take off the hoses, put the new one(coolant reservoir or sensor, depending on year of your 8) in, and reverse the process.

 

Mt low coolant light has been on for about 15000 miles. It's the chest sensor in the overflow tank. Their doesn't bother me and I'm not concerned with it. I do have a new mazda tank and when the time comes to sell my car I will replace it. You are missing an obvious issue here though. Does no one pay attention to the temp gauge in their cars. Bottom line if it starts to run even slightly above normal shut it down. Now if have a done a drain and refill did you make sure there's no air in the system as this can cause issues as well.

 

So, how often do you look at your temp gauge?
The gauge is notoriously undependable, and by the time it starts moving, the engine is already overheating.
If you had a sudden radiator leak do you think you would notice the needle move before it overheats?

I mean seriously, WTF?!

Why are people rationalizing a potential $5000 problem instead of seeing the logic of a $125 repair that could save someone's engine?
Just baffling.

 

The real question here is why are you having such a WTF hissy fit over what other people do with their cars??, this is mind boggling to me. If some one wishes to disconncect a percieved usless piece of equipment so what? move on and let it be. The only real answer in my opinion is to install a dash mount temp gauge so you know the exact temp at any given second ya think lolo?.

 

Because if you stay here long enough, you'll see people overlook a small problem, like a sensor, only to come back in 2 months asking why their motor doesn't keep idle. This is a support forum for the RX8, our advice can't be "yeah man do whatever, it's all good".

 

It is also an issue with S2s. My sensor was faulty, would turn on whenever sustained driving over *cough* certain speeds and turn off immediately after slowing down.

 

I try to help new members who may not know a lot about our 8s.
People minimalizing the risk of disabling a warning light because they're too cheap, lazy, or for whatever reason to fix it, is wrong.
Someone may read "it's no big deal", trust the source, and it could cost them a new engine.

 

BigC, you are blowing it out of proportion. Mazda sells a reservoir without the coolant level sensor and one with it, it's an option.

If you are overheating the gauge will move, it's not totally useless and the idea that the engine is toast if the gauge moves is just untrue. It is set to move at a certain temp because that is the way Mazda designed it and according to Mazda, up to 243F (or 248F can't remember) is considered safe. Plenty of track guys hit temps in that range on a regular basis and have done it for years. Now if you are hitting those temps on the street then of course you have problems and by that point your gauge should have moved and you should be smelling coolant.

If someone needs a gauge to tell you when your car is at critical temp then you should not be driving a sports car. If coolant temps are something that you really worry about then there are plenty of other options (normal gauge OBD solution, etc) that can sound an alarm once your temps reach a certain set point. Like I said before, plenty of cars don't have coolant level sensors (such as my Acura and my Jeep).

 

Agreed.
While driving my first car, an old Saab 96, the temp gauge suddenly rose and, more importantly, the warning light came on; it was the red light that caught my attention. I pulled over, opened the hood and discovered a small hole in the bottom of the plastic overflow tank. The tank had somehow come loose from its mount and came to rest against the engine block, which burned the small hole. That won't happen with our cars, but still, a rock could do that to the cooling system, and I would want to know immediately.

Also, if I'm not mistaken, Mazda redesigned the original tank/sensor. The available replacement tank is the redesigned version.