Since I put on the Omori water temperature gauge, I've made an interesting observation.

The stock gauge points near the 'normal' position between the temperatures of around 50-90 degrees Celcius! I guess our stock gauge isn't all that precise.

I'm still a little concerned about my water temp hovering between 85-90 C around town. 1MAX2NV said his stays at 180 F (82 C). I noticed that with the A/C on, it stays pegged at 80 C. Do you think I need to change out the sensor that activates the engine fan?

 

The themostate opens at 180F. I only had mine for a little while. It usually stays below 180F during cold days. It gets above 180F when it's warm outside. I think it will be even higher like in the 200F-210F range during hot summer days. I don't think there is anything wrong with your fan switch.

 

The guages that have no numbers are purposely set up to behave this way. Most of the time, they work like this: Somewhere around 120F, the gauge begins to read in the "normal" area. The gauge will hold steady until the water temp gets to 215F or so, then it will begin to move up again until you peg the gauge and boil over somewhere in the 220-240 range (depending on your a/f mix and the pressure in your system).

Many thermostats open around 180F and allow water to begin to circulate through the radiator. So, if all the other stuff in the car is operating properly, your water temp will hover right in this area once the car is completely warmed up. Probably +/- 10 degrees. (If we had a gauge with temp #'s on it, you would see this happen.) It is normal for the temp to fluctuate slightly within a few degrees of the thermo rating as the system maintains a balance between the thermo and the coolant temp by opening and closing the thermo and cycling the fans on and off.

This operating temp is designed in to the engin specs so that the engine operates in its most efficient range. Too cold = lotsa emissions. Too hot = reduced longevity. BTW, that's why your car can sometimes fail emissions if your thermo is bad and it is running too cold. And, that's why many cars have precats -- because when the engine is cold, there's lotsa junk coming out of the engine and the EPA wants things clean as the car warms up. BTW, thermo spec has little/nothing to do with spark plug heat range.

DK how true this is, but I've heard that one of the reasons that cars have the plain temp gauge is because drivers couldn't properly interpret "normal" fluctuations in operating temperature as being "normal". They would bug shops/manufacturers to find out why the temp gauge was moving around all the time. Something MUST be wrong, right? Wrong! Removing the numbers and designing the guage to sit still over a wide range "dumbed down" the data point for the driver so that people with less knowledge about how engines worked wouldn't get bent out of shape when the guage was bouncing all over the place (see: old MG, Triumph, BMW, etc) Holding the gauge steady over a wide range meant that no one noticed it until things got bad.

BTW, while it is important to have your car up to temp before really getting on it, the water temp is only 1/3 of the story. It is best to wait for a bit after the water has warmed to ensure that the oil and the tranny/diffy fluid are up to temp as well. These usually take a little longer than the water and aren't tied to the temp guage.

 

SCC Mag did a test similar to what you guys are talking about. they ested a sentra, and found that the temp stayed in the middle through lots of different temps.

 

SCC Mag did a test similar to what you guys are talking about. they ested a sentra, and found that the temp stayed in the middle through lots of different temps.

 

Thanks guys!

I'll watch it for awhile...no matter. I just set the alarm at 95 C (203 F)...

 

[QUOTE]Originally posted by Chunger
[B]Thanks guys!


Do the sensors that operate the stock temp gauge also tell the ECU what the engine temp is, or do they use seperate sensors? The wiring harness is bad on the sensor that operates my gauge - if it isn't tied to the ECU, I'm not too worried; but if it is, wouldn't the computer make the engine run rich all the time?

 

There are two stock water temp sensors. One is for the gauge and one is for the ECU. Nevertheless, you should have a working water temp gauge. Overheating will crack the head or the head gasket. It could also seize the engine. It's not worth the risk IMHO.

[QUOTE]Originally posted by MaxKlinger
[B]