So my wife's 2018 X4 M40i has a bad coolant temp sensor. From everything I have seen online it says that I am supposed to get the air out of the coolant system after replacing the sensor because the air may damage the system? I've never heard of this sort of thing before but I wanted to get some advice on it. The coolant reservoir doesn't appear to have a "bleed screw" so if I am supposed to bleed the system of air where/how would I do this? Also for context, from my research this is apparently the N55 engine. Thanks in advance!

BMWTroubleU wrote

So my wife's 2018 X4 M40i has a bad coolant temp sensor. From everything I have seen online it says that I am supposed to get the air out of the coolant system after replacing the sensor because the air may damage the system? I've never heard of this sort of thing before but I wanted to get some advice on it. The coolant reservoir doesn't appear to have a "bleed screw" so if I am supposed to bleed the system of air where/how would I do this? Also for context, from my research this is apparently the N55 engine. Thanks in advance!

it this way you may need to do it a few times

or if you have access to an air compressor and use a vaccum fill https://amzn.to/3TQxHoT

Burr001 - Thank you!! Her's doesn't have that extra reservoir from what I can tell, so maybe it'll be a little easier! I appreciate it!

BMWTroubleU wrote

Burr001 - Thank you!! Her's doesn't have that extra reservoir from what I can tell, so maybe it'll be a little easier! I appreciate it!

2018 m40i only has one?...there is the coolant for the main and coolant for the manifold- charge cooler...b58 engine?

Yep, as far as I can tell it only has one and it doesn't have a bleed screw or anything. The temp sensor is not that hard to get to. I'll take a pic and post it. She is in healthcare so she won't be home until later. I thought it was the N55

The only reservoir I see is the one on the top right but there has to be another below the plastic shroud on top of the engine.

I replaced the coolant temp sensor but the check engine light is still on and the temp gauge on the display isn't working. Any thoughts?