N54 coolant sensor ?

[SlowE93]

So, took the slow mobile out today. After leaving a drive thru, I got a warning of high coolant temps. I look down at my jb4 app and indeed, water temp shows 233°F. Then it drops to 206. So I drive off and it literally jumps from 186, to 206, to 23x then back down to 209 and settles there. Then on my way home, same thing. Jumps to 230s then in 1 second down to 186, then the next second 199.
I am thinking coolant sensor as the wp and thermostat were replaced about 12k miles ago.
Also the fan never kicked on full blast like a wp failure.
No codes, not even shadow.
Thoughts ?
Also on the N54, where is the sensor located ?

 

[JohnDaviz]

No idea. Change the sensor. It is in the Head

No.7

RealOEM.com - Online BMW Parts Catalog

BMW parts 3' E92 335i Cylinder head, electr. add-on parts

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[SlowE93]

No idea. Change the sensor. It is in the Head

No.7

RealOEM.com - Online BMW Parts Catalog

BMW parts 3' E92 335i Cylinder head, electr. add-on parts

www.realoem.com

Yeah, I foumd the sensor just a few minutes after posting this. Replaced it and it is more stable, but still fluctuates quite a bit. No ses or anything though.
Looked at some old logs and its always done this though. Yesterday was strange because it threw the ses, I saw tenps stuck at 233°F And it gave me a warning on I drive.
No codes and temp dropped as fast as they went up.
Anyway, thanks for responding. I took the car out last night and so far, so good.
Confused on why oil and trans temps do not behave that way. Those are always more stable in logs.

 

[SlowE93]

Here is the old one.

 

[SlowE93]

The tip has a really shiny spot on it. Very small, but wonder if it was just on its way out.

 

[Jeffman]

Any chance you have air bubbles in your coolant system? I can imagine air bubbles resulting in this kind of behavior. Just to be sure check coolant level cold, and operate electric coolant pump bleed procedure: heater fan lowest, highest temp, foot on pedal 10sec. Open cap and watch coolant flow into expansion tank.

 

[SlowE93]

Any chance you have air bubbles in your coolant system? I can imagine air bubbles resulting in this kind of behavior. Just to be sure check coolant level cold, and operate electric coolant pump flush procedure: heater fan lowest, highest temp, foot on pedal 10sec. Open cap and watch coolant flow into expansion tank.

I thought the same thing but last years logs show same behavior, just never triggered any warnings in I drive.
Took the car out for a nice drive yesterday and all was fine. Maybe just the sensor was about to go. I will re-bleed the system tomorrow but dont see how it would get any bubbles in the first place.
Last thing I had done months ago was mickey mouse flange and bled the system back then.
Thanks for the response !