That's a good idea, but if he has a bad sender then that data is going to be flawed just as the data reading out from the gauge is flawed.

Thanks guys for the input.

A little more detail...

My heater doesn't seem to blow warm air as soon as it used to.

I checked my coolant temperature with a scan tool when it was fully warmed up. It read 179 °F with the gauge slightly to the left of center.

My first guess was that Mazda service left out the thermostat during the engine replacement. I took it back and they confirmed that there was one there and replaced it with a new one. Supposedly the new engine came with a new thermostat. The replacement thermostat didn't make any difference at all.



That's my guess too, and since the heater is too cold buy a new t'stat a few degrees warmer (183*/185*) and put it in anyway, can't hurt.

The temp gauge really isn't accurate as many have mentioned on here. Mine doesn't move from just left of centre with engine temps anywhere between 170 and 205'F.

It rises in small jumps if you're bored enough to sit and watch it warm up, too.

He already had another thermostat put in.

OK, 179 degrees full operating temp is near enough for winter. Point 1, that the needle only reaches 3/8s or slightly higher at full temperature is how my car has always operated, and I consider that normal.

Point 2 - This is not right. My car used to do this when I was on the K and L flashes back in '03 and '04. That was caused by too much fuel being dumped into housings at certain RPMs, and was eventually resolved by the M flash and subsequent flashes.

5 to 7 miles to warm up in cold temps can be right. 35 to 46 minutes to reach operating temperature seems really long to me. My car does it in 15 minutes or so in stop and go temps with ambient temps outside of around 30F. If it is in the single digits, then 35-45 minutes is possible.

I also wonder if your old engine wasn't running hot and you got used to that.

In any case, I don't know what else to tell you. Best of luck.

AND Racing Beat states:


RX-8 owners, are you aware that the "gauge" that appears on the dash of your RX-8 is not actually a functional gauge? Have you ever seen it move? Not only have we discovered that this is a non-operational gauge, but there isn't even an oil pressure sensor on the engine! Nope, the gauge will never move from the position that you see. (There is a functioning oil level sensor and dash light.) Remedy this with the installation of your own gauge(s) in your RX-8. To monitor water temperature in your RX-8, also see our Water Temperature Sensor Adapter unit.

http://www.racingbeat.com/RX8/Oil-System/11803.html

For $450 you can correct this attractively http://www.mazdatrix.com/8interior2.htm

That's interesting about the oil pressure gauge. I looked in the service manual and the oil pressure sending unit is referred to as an "oil pressure switch". That confirms what Racing Beat is saying.

The engine temperature gauge is definitely not just an idiot light though. I mean it does move after all.

Now back to my apparent engine temperature problem...

I intend to log my temperature data with my scan tool. If I get anything useful I will post it. The fact that the gauge doesn't reach half-way may be normal to some owners but it is different for my car and I would like to know why.

Thanks again for everyone's input.

In cold temperatures I would expect to see around 180F. That's what I typically see on my Analog Racing beat gauge picking up off the heater core inlet hose. Hot 210-215. 220 and up is when I get nervous.

Racing Beat Says:
 

http://www.racingbeat.com/mazda/perf...r-cooling.html

"With any rotary engine application it is wise to monitor the water and oil temperature of the engine. This is particularly difficult in the RX-8 because Mazda chose to have a water temperature gauge that does not give a linear, proportional reading. What this means is that, as the actual water temperature rises to about 170° the gauge stops moving, when the engine coolant temperature reaches 205° it starts moving again! This gives you a false impression of the engine cooling in cases where knowledge of increasing engine temperature might cause you to drive to lessen the heat load on the system. We disagree with this approach to informing the driver! For this reason, we developed a module for the RX-8 which features a set of calibrated water, oil pressure and oil temperature gauges."

It would be good to read the whole article as it's very informative.

That's pretty interesting. Thanks for the link. At least it isn't as dumbed down as the oil pressure gauge.