Has my gauge gone haywire?

[EZT]

We all know how inaccurate the water temp gauge is, but mine started acting really funny as of today. Mind you, air temperature was low 70s and radiator is full of fluid. I happen to notice my gauge passing by the 7th dot, it continues to climb almost to the beginning of the H, maybe the 12-13th dot and then it steadily drops back to 6 then 7. My entire drive to work which is roughly 40 minutes my oil temp stays right at 215, but the water temp dances back and forth the entire way.

Return trip home, air temperature is now 50 degrees. Oil temp stays at 200 degrees. Again, the water temp gauge dances back and forth the whole way home. Any thoughts?

[Jordo!]

If not a failing sensor, thermostat sticking maybe?

How many miles?

[SouthArk370Z]

If the water temp is changing quickly and/or jumping 2 or more dots at a time, I suspect the sensor or wiring. If the swings are slow and steady, then Jordo! may be on the right track with the thermostat. Or it could be a faulty readout.

Try monitoring water temp directly from the ECM with an ODB/CAN monitor.

[EZT]

83,000 miles. The swings are pretty fast, immediately moving several dots. Will try to monitor through scanner.

[theDreamer]

Have you checked fluid level?
When I had a leak and my fluid dropped down to very little I would get a swing temp, jumps up and then back down. Inspected the car and found the leak.

[1slow370]

yup you may has some air in the motor not good, your heads might not have coolant in them and that is how head gaskets get blown.

[Spooler]

^^^^^This

I would check for an air pocket and if you have one, look for the leak.

[1slow370]

and if you can't find a leak, well, I know where your leak is and it isn't pretty.

[EZT]

My fluid levels appear to be fine, right at the max line on the over flow reservoir.

[1slow370]

let the car cool off and pull the cap on the coolant neck.

[Read T]

Originally Posted by EZT

My fluid levels appear to be fine, right at the max line on the over flow resevoir.

Check the radiator cap, and even then you could have a fluid pocket in the block or by the sensor. I know S14s were notorious for this.

[EZT]

Was not at home all day, pulled the radiator cap for a while and no effect still. Beginning to think I may have a problem for sure though. I have the CSF aluminum radiator, but it's had a small leak from the start (got it used). I recently tried some Radiator Stop Leak for aluminum radiators and my fluid level has stayed perfect sense. However, from what you guys have been saying I may have a bigger problem now.

[Tadpole]

Nah, sounds like a sensor to me. My fuel gage dots did the same thing. I took it to the dealer and they replaced both sensors and no more dot issues

[1slow370]

Originally Posted by EZT

Was not at home all day, pulled the radiator cap for a while and no effect still. Beginning to think I may have a problem for sure though. I have the CSF aluminum radiator, but it's had a small leak from the start (got it used). I recently tried some Radiator Stop Leak for aluminum radiators and my fluid level has stayed perfect sense. However, from what you guys have been saying I may have a bigger problem now.

was the neck full to the lip of coolant when you pulled the cap? Did it come bubbling out when you pulled it.

[EZT]

Originally Posted by 1slow370

was the neck full to the lip of coolant when you pulled the cap? Did it come bubbling out when you pulled it.

It was still sitting in the same spot I left it, right at the Max line on the reservoir. Nothing came bubbling out.