I've been asking questions in a couple of other threads now but thought it might be better not to pollute others' threads but instead create my own. So here goes:

My 545 does not seem to reach normal operating temperature, even after long drives. And the temperature increase seem to be very slow. I made some searches on this eminent forum and found one very useful thread with instruction in how to access the coolant temperature sensor in the OBD system (see problem solved; engine 525D not reaching operating temperature). According to the OBD the temperature in my car does not go above 70?C even after 1hr driving (it's 7?C outside).

I thought it was a faulty thermostat so looked for advice on how to change it, and found this thread:
Replacing thermostat?, anyone done this before?. But in that thread they also talk about another thermostat. Does anyone know if the 545 has a second thermostat?

Further to the problem, while driving home yesterday I got stuck in traffic, moving very slowly or not at all. I heard the electric radiator fan go on and stay on until I got into my garage. And still the temp sensor showed just over 70?C! And when I got into the garage I checked the flaps in the grill and they were closed. Isn't it a little strange that the flaps stay closed and the electric fan tries to blow air throught the radiator? And this at 70?C!

So now I'm thinking it could be a faulty sensor, maybe in combination with the thermostat? Does anyone know where the temp sensor that gives the temperature you can see in the OBD is located? And is that a different sensor than that controlling the electric radiator fan?

I'd appreciate some advice on how to go about this, if anyone knows. For info, I went to the "stealership" yesterday and they want what corresponds to 600 USD to replace the thermostat (quoted part cost is 100 USD).


Background:
The first time I noticed a problem was about a month ago after a cold (-15?C) night parked outside, the car didn't warm up even after an hour drive on motorways. Granted it was still cold out but I couldn't even get the temperure up much inside the car. I have since noticed that the tick marks move up a lot slower and their final position seem to vary with outside temperature, when it's colder they don't go up as far.

 

Go to realOEM.com that may help u.

 

Yes, I did that, but apart from the main thermostat the only other seem to be related to the HX for the auto tranny? (#13 in the third image below)

Images from realoem:

 

I bought a new thermostat, will try to find the time to install it this week-end. Hopefully that will solve the problem.

 

Replaced the thermostat and the temp went up to 96?C!

Couldn't find how to manually bleed out air that must surely have been trapped in the system during the replacement work, does anybody know?

Performed the automatic bleed according to this post (except for attaching a charger, didn't have one handy).

 

do you have a DIY for the replacement thermostat