[bugsy]

Hi Guys,

Over last days I've noticed that oil temperature (on the dashboard gauge) barely raises when driving on highway and stays at minimum of 70C (158F) and only if pushing really hard it gets to 80C (176F), but more in town traffic only.
When car was parked and engine idling for 15-20 minutes it got a bit higher, but as soon as started to drive it went down immediately.
Outside temp is around 0C (32F) - freezing point and got down over last days from 20C (68F) when oil temp was around 90-100.

Suspicion is on thermostat or anything around that cooling circuit is open at max hence difficult to raise engine temperature. Another factor to that is that couple of months ago when it was still nice 23C (73F) outside car was at mechanic, where they were replacing starter and "forgot" to plug in one of connectors and as result I had Tank-venting valve error, fixed by simply re-connecting cable as they disconnected it earlier.
It was pretty warm outside till now hence I suspect the problem might be similar and just not visible till it got cold.

Trying to identify it with INPA/DIS, no error codes around thermostat were present, just NOx related (known issue requiring replacing NOx sensor for ~500$).

Is there a way to troubleshoot this further with INPA/DIS and if not, what would need to be verified to narrow down the root cause? I've lost trust in that mechanic and am wondering if this could be troubleshoot/fixed by an Indy without INPA/DIS until I find a good one with BMW knowledge?
I have INPA/DIS and can run tests, so this married with good mechanic would be much better solution than the Indy I used till now as they caused me more issues than expected, imagine situation where I got call that car is ready, 30 minutes later arriving at the garage I'm getting information that engine can't be starter, funny enough they were able to drive the car into washing room but after washing couldn't start it again then claimed it to be starter and wanted to charge me double the value of BMW starter. Some days later as soon as I drove out after replacing starter, started to get MIL (engine malfunction). The garage claimed error had to be there, etc. So after resetting it twice I started to figure out what's going on and they were rejecting any suggestions that they were involved in it... till I've forced them to check connectors on that valve - as I was at inspection it has been confirmed that plug wasn't connected to the socket, grrr....

So I lost confidence in these guys and suspect that this thermostat issue might be a plug not connected into a socket or another result of their activities.
Hence question how to troubleshoot thermostat and if could use normal garage without BMW knowledge.
How to check if thermostat is stuck open? Recently I've done oil change too, but could it have an impact? My E93 has N53B30 whilst N54 has thermostat for oil cooling close to oil filter, but do I have similar? Could it be stuck open and if yes, where is it to find it?


Thanks in advance.

[Three_thirty_I]

I've been down this road with my N52 - same sort of oil/coolant temp that you have, typically mine is between 74 and 84 degrees Celsius, but on brief occasions it will go up to around 96 degrees Celsius, then shoot back down (this is where the thermostat is rated to open, well 97 degrees Celsius to be accurate). And the kicker, when this issue was pointed out to me back in 2012, it was suggested that I replace the thermostat, but then was told to start by replacing the temperature sensors. So I did that first and gave the engine fresh BMW coolant with distilled water while I was at it. No difference. I will point out that my E90 of course doesn't have a temperature gauge on the cluster, which is why I never knew about this until it was spotted at a specialist whilst taking live readings. So for me to see this I need to have the coolant temp in hidden menu open.

I have also never had any error codes to suggest anything being wrong, but then in early 2015 I decided to replace the thermostat with new OEM part, and guess what? It's still running at these cooler temps all the time. So for mine, this is a ongoing conundrum!