That does not look like the coolant temperature sensor, although the part has the same type of connector. It looks like the SAP vacuum control solenoid that is located on the underside of the rear of the intake.

The engine coolant temperature sensor is located in the rear drivers side of the cylinder hear down near the engine block mating surface.

https://www.bimmerfest.com/forums/showthread.php?t=893157

https://www.youtube.com/watch?v=3WE7sb6L6OI

These coolant sensors rarely fail, not sure this is the cause of your problems.

Cold start problems are historically due to vacuum leaks on these engines, there are a LOT of them as these cars age.

Solve your misfires, lean codes, rough idle - https://forum.e46fanatics.com/showthread.php?t=897616

What specifically is the erratic temperature gauge issue you are seeing? This can be due to air in the cooling system or other problems not related to the temperature sensor.

 

Thank you very much for identifying the pictured connector! I've seen that video of replacing the engine coolant temp sensor without removing the intake manifold, but can't make progress until I can actually locate the thing for removal. Lots of wires and hoses in that area make it difficult to see anything. Not sure if removal of intake boots and DISA would help or not.

Car has had a consistent P0118 code - Engine Coolant Temperature Circuit High Input. The P0118 doesn't come back right away after clearing codes, but it always comes back eventually.

The temp gauge displays normal most of the time. Sometimes it drops to full cold and sometimes it will peg full hot. In either or the extreme cases abnormal reading lasts for less than a minute before returning to near middle of the gauge. Most common time for the erratic temp gauge display is when engine is cold.

Coolant system radiator, expansion tank and hoses were replaced about a week ago. No issues were experienced bleeding the system (nose up on ramps, filled expansion tank with 50/50 BMW/distilled water until solid stream of coolant came out of bleeder opening). Coolant level has held steady over past week with bob level with top of expansion tank cap - approx. 1000 miles of highway commuting. Cabin heat seems to work fine. The P0118 and erratic coolant temp gauge showed up both before and after the coolant system work.

Regards,

Joe M in WV

 

Thank you very much for identifying the pictured connector! I've seen that video of replacing the engine coolant temp sensor without removing the intake manifold, but can't make progress until I can actually locate the thing for removal. Lots of wires and hoses in that area make it difficult to see anything. Not sure if removal of intake boots and DISA would help or not.

Maybe these pictures can help. Note that in the close up picture, the thick cable/wiring harness is 'behind' the temp sensor, which means that the temp sensor is rearward (closer to firewall) than the wiring harness. I think that means (but am not 100% sure) the temp sensor is just rearward of the thick cable going between cylinder 5 & 6 in the wider view picture.

 

Usually when the temp gauge goes all the way to the red before the car is even on, it's a communication error with the DME. I suspect there's oil and/or coolant contamination in the DME plugs

 

http://forum.e46fanatics.com/showthread.php?t=1052977

http://www.bimmerfest.com/forums/showthread.php?p=9977321#post9977321

http://forum.e46fanatics.com/showthread.php?p=16833498&posted=1#post16833498

http://forum.e46fanatics.com/showthread.php?t=870338

http://site.ecudoctors.com/tech-data/BMW_325/BMW-325-M54-DME-ECU-MS43-Pinout.pdf

https://forum.e46fanatics.com/showthread.php?t=1236408

 

More closure - Engine coolant temperature sensor was located and replaced without intake manifold removal. The sensor is much more toward the center of the car than I had imagined.

Once the cabin air filter, air filter tray and plastic divider between engine and shock tower were removed, there is just enough room to get an arm through to the sensor. The sensor is pretty much pointing toward the small space between back of block and the firewall.

A crow foot oxygen sensor socket on 3/8" extensions worked with much less drama than expected. The socket was first placed on the sensor, then extensions attached to the socket, then ratchet attached to the extensions. There didn't seem to be enough room for my hand to get back there with the socket, extensions and ratchet assembled together.

Thanks much for the fountain of e46 knowledge here. The engine coolant temperature sensor eventually failed completely, making warm starts difficult and heaping additional work on the starter.

Joe M in WV

 

Congratulations!

 

Another way to remove it is to buy a 22m box-end wrench and cut it in half. Then use either end to loosen. As mentioned, It usually comes free with just a little effort.

 

Nice! Good to know that its doable.