BMW X3 2005 Temperature Issue

[Hudson9028]

Good morning.

I've done a bit of research into this as well as used the search function but would like to confirm before I get any work done.

My temperature gauge used to stay in the cold, it would occasionally move but still would not reach operating temperature. I then had the thermostat replaced which seemed what I thought had cured the problem for I think the first journey, now it seems to just do what it wants, takes a good 10 minutes of driving before it moves and when it does it never goes to the centre, if I'm moving the temperature seems to go down to maybe the 1st or second marker but then goes back up when idling. Fuel economy is sat at around 38mpg according to computer.

Engine is 2.0l diesel, this problem is really starting to bug me as I've read up on the negative impact this can have on the engine. Have I possibly got another dodgy thermostat or is it something else?

Thanks in advance.

[hoodmeister]

Strange temp sensor readings can happen when the cooling system has air in it. I would make sure you've bled the air out properly.