Coolant Temp fluctuation?

[dnguyen1963]

If the needle stuck at 3/4 during normal operating condition and assuming that your coolant system is in good condition then I would check the SI/Main board for corrosion and breakage in solder lines. Use an IR gun to verify the actual temp of your engine.

[MR E30 325is]

This screams a small bubble of air in the coolant to me.

If nothing else pans out I'd bleed the coolant system.

[bimmerR75]

Also, check the grounding nuts on the back of the cluster. Loose ones can cause temp gauge fluctuations as well.

I have been meaning to do that. Going to work on that tomorrow and see if that fixes the issue. The gauge at start up is getting stuck at the bottom, if I tap on the cluster a couple times lightly it pops up to the blue where it should be at start up.

The grounding nuts may be the issue, will tinker and report back.

Thanks everyone!

[bimmerR75]

During what driving habits is this happening? Sounds like a weak clutch fan to me.
Is the needle moving or jolting to the 3/4ths mark?

I use it as a daily driver, it typically will move throughout the day between the 3/4 and half during city driving. Highway it stays at a solid 3/4. Its slowly moving.

[estoguy]

Also, check the grounding nuts on the back of the cluster. Loose ones can cause temp gauge fluctuations as well.

[ak-]

During what driving habits is this happening? Sounds like a weak clutch fan to me.
Is the needle moving or jolting to the 3/4ths mark?

[bimmerR75]

Hey there,

Not sure if im going crazy but my auxiliary fan seems to be working fine, changed out the radiator temp switch with the bavauto 81/89c switch. Yet it seems my coolant temperature is constantly moving in between the 3/4 (from the middle) mark and the middle and back to 3/4 or in between. Is it normal for there to be slight variation or should it consistently sit at 3/4?

Until recently it basically sat at 3/4 but lately its been moving and a bit more temperamental.

Coolant level seems to be at the right mark when engine is cold, but perhaps theres not enough and thats causing the fluctuation?