cooling system problem // please help...
 

alright WTF ? if its not one thing its another with my rx8 ,,, cooling system display usually a little below half on the guage ,,, but lately even on normal steady driving the tepm. guage shows a little too warm . not to the overheating point but the guage shows about 3/4 to the hot side in other words hotter than normal ,, it would fluctuate it will get warm then goes back to the middle and back and forth ,,, i changed my radiator hoses they were a little soft i thought that was the problem but it didnt help at all,, im kinda lost with this one so PLEASE HELP ... i figuered the thirmostat and the water pump either works or dont they dont have a middle and my problem is in the middle of normal temp and overheating ,,, please help

Thermostat or cooling fans most likely...

Does it overheat at idle or stop and go traffic...or on higher speed runs?

Do you even have a S2 ?

Cuz seriously I think you dont have a S2.

Did you ever get an answer to your question or solve your problem? I'm having the exact same thing happen to me. Fans seem to be working okay and the coolant level is fine. The heat seems to go up with the revs even when traveling at speed with plenty of air flowing. At idle the temp drops back down to the normal level.

Any ideas? Anyone?

mine has done this recently as well. although, it was a very hot day, and redlined once or twice. then at idle the temps would rise. I had to turn on the heater to get them back down.

When the gauge starts to move, the coolant temp is at 232 degrees. Just thought you might like to know that.
Might want to read through this if you have the time. LINK

Agree with Easy....

There is also a very remote possibility that your Temperature Sender Unit (Behind Water Pump) which in turn is connected to your Dash Temp Gauge is faulty.

If these Brass sender units play up, you can get false readings...but AFAIK they are a very reliable unit.
Have been used on Most Mazda's over the past 20 years...like 1991 Mazda 626,2,3,6,MX-5, 323, B Series..etc.

Genuine Mazda Part Number
B593-18-840A Sender Unit
9956-41-200 Washer

I'm wondering if this might not be it. I would think that if my engine was running hot enough for the gauge to move out of the normal operating temp zone, then my engine would seem pretty hot if I popped the hood. Right? I just popped the hood after driving for a bit and having the gauge randomly jump around and the engine bay seems almost cool. I've experienced it way hotter before and never had any gauge fluctuations.

The gauge sits at normal and then will jump up and then it will go back down to normal. It seems to jump up when the revs are up, but it moves back down to normal pretty fast.

this is why the 8 should have come with a real gauge from the factory.

You could check the wiring connector plug to the Temp Sender Unit (behind water pump), see if it is loose??

Could also be the DASH Gauge itself, BAD news is you can ONLY replace this part with a Complete New Speedo Head Unit...!!!

Oh, one other piece to my puzzle: My brakes were pulsing a little, so I went out on a back road near my place and did 5 or 6 runs up to 70 with a hard brake. It started happening after that, that same day (Sat 6/8/10). Maybe the negative G's loosened something.

How many miles has your 8 done?..

A pulsating feel through your brake pedal is usually brake rotors (front) with an uneven wear/surface...or more than likely if you are doing HARD stops from 70 MPH it is your ABS working which is normal.

Do you feel a pulse when normally braking??..if so..

Generally a machining and new pads would rectify this, in the US you don't seem to machine but throw away rotors for new ones.

My 8's got 78K on it. The pulsing was under normal braking. I've read threads here arguing about uneven wear or "warping" being a myth and that it's built up pad material on the rotors that causes this. A few hard stops from 70 seems to have fixed the problem, so I'm thinking that is was just built up material. But now I'm getting this overheating issue (possibly incorrectly), so I wonder if the hard stops had anything to do with it.

An update on my issue. I pulled the car apart over the weekend so I could take a closer look at the fans. Everything looks and works normally.

I also flushed the coolant. After flushing the coolant the first two time I drove the car it was even quicker to rise above the normal temp mark. I was thinking, "great, I made it worse!" But after that it suddenly stopped. I went for a long drive yesterday with some freeway and red lining it several times and the temp gauge didn't budge.

I'm not going to claim it's fixed yet. I would like to take it for a spin on a day with higher ambient temps (even though it's been doing the overheating thing in lower temps like we're having now). But maybe that did it.