Need Help Determining Root Cause of Temperature Needle in Red - SOLVED

[eacmen]

Does it go into red immediately after you turn it on? If its immediate might just be a sensor issue. Have you logged inlet and outlet temps?

With the engine running but still cold do you see coolant flowing into the reservoir from the overflow line? This should indicate that coolant is at least flowing…

[sapote]

Update. I finally had a chance to get back to diagnosing things. Last week I turned the cover, let it run for a few minutes, and saw the coolant gauge needle climb into the red zone again. The upper coolant hose warmed up, while the lower coolant hose stayed cool to the touch, but I didn't let the car run long enough to get it up to temp due to the needle position.
I spun the water shaft and checked for play. There's practically no play, and it has resistance similar to new

So did you find out what caused the grinding noise in the first post?
In this case I would be interested to crack open the bleeder screw and see if any gas coming out, and drop some water on the side of the head and see if it boil quickly to verify if the gauge showing wrong temperature.

[0-60motorsports]

Update. I finally had a chance to get back to diagnosing things. Last week I turned the cover, let it run for a few minutes, and saw the coolant gauge needle climb into the red zone again. The upper coolant hose warmed up, while the lower coolant hose stayed cool to the touch, but I didn't let the car run long enough to get it up to temp due to the needle position.

I haven't turned the car over in a week. The needle is still pegging outside the red zone (see pic).

I decided to pull the thermostat and the water pump since I needed to perform a coolant flush. I checked the thermostat via the boiling water method, and it opened. I spun the water shaft and checked for play. There's practically no play, and it has resistance similar to new. This leads me to believe the hardware (at least the parts I've checked) are fine.

Check the coolant temp sensor under the intake manifold. Check the wiring for it too.

[bimmerfan08]

Does it go into red immediately after you turn it on? If its immediate might just be a sensor issue. Have you logged inlet and outlet temps?

With the engine running but still cold do you see coolant flowing into the reservoir from the overflow line? This should indicate that coolant is at least flowing…

It's immediate. It's actually consistently reading near red/in red. Problem with the gauge itself?

Pulled temps. All seems fine.

[0-60motorsports]

It's immediate. It's actually consistently reading near red/in red. Problem with the gauge itself?

Pulled temps. All seems fine.

did you try a gauge reset? or pull out the cluster and disconnect and reconnect the connector. Maybe it'll make a difference,

[bimmerfan08]

did you try a gauge reset? or pull out the cluster and disconnect and reconnect the connector. Maybe it'll make a difference,

I haven't. I don't drive the car much these days. If my memory is correct, the coolant temp gauge does a full articulation and returns to the cool (blue) section as part of the startup sequence, yes?

Where can I find the procedure for the gauge reset?

Edit: I found instructions for pulling the cluster and manually resetting the gauge if I need to.

https://nam3forum.com/forums/forum/main-forum/e46-2001-2006/74524-temp-gauge-needle-sits-high-how-to-reset

[0-60motorsports]

I haven't. I don't drive the car much these days. If my memory is correct, the coolant temp gauge does a full articulation and returns to the cool (blue) section as part of the startup sequence, yes?

Where can I find the procedure for the gauge reset?

Edit: I found instructions for pulling the cluster and manually resetting the gauge if I need to.

https://nam3forum.com/forums/forum/m...h-how-to-reset

https://www.youtube.com/watch?v=tnIyNNn-UM0

[bimmerfan08]

https://www.youtube.com/watch?v=tnIyNNn-UM0

Thanks!

Will try this soon and report back.

[bimmerfan08]

Using a scan tool try to manually turn the aux fan on. At the temps you were seeing the aux fan should have been on full speed.

Never followed up on this. I did manually activate the fan. It's working as normal.

[bimmerfan08]

Did a gauge cluster reset. That seems to have solved the needle sticking in the red zone issue for now. Thanks, 0-60motorsports.

Will reassemble the cooling system and make sure everything functions as normal.

Still haven't pinpointed the sound I heard on startup a few weeks back.

[0-60motorsports]

Ok that's good. Hopefully it's resolved now.


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[bimmerfan08]

First post has been updated for future troubleshooters. Once I have the system reassembled and the car tested to ensure it's fine, I will update the title to "solved".

[eacmen]

At least the engine wasnt overheating! I did not know about this cluster reset procedure - learn something new every day!

[Slideways]

Did a gauge cluster reset. That seems to have solved the needle sticking in the red zone issue for now. Thanks, 0-60motorsports.

Will reassemble the cooling system and make sure everything functions as normal.

Still haven't pinpointed the sound I heard on startup a few weeks back.

Did you ever replace the alternator? Worn bearings can make a grinding noise.

[bimmerfan08]

Did you ever replace the alternator? Worn bearings can make a grinding noise.

I have. Not too long ago (forget the year off the top of my head). The other pulleys have been replaced in the last 3 years (10k miles).

I'll put the car back together and give it another listen.