Pistratoaie

100+ sounds high, I was looking more towards 90-100. by my dash reading in hidden menu, above 50mph it is between 72-78. Much too low, I have changed the thermostat hoping to fix this issue after a radiator replacement. But there was no change, I'm not too knowledgeable on electrical, without full research that is.

sanjsanj

if yours is an auto, there is a thermostat in the oil cooler which could have failed.

Diesels with a new thermostat run at 90C on the highway (even if it's -5 outside, I've checked!) - petrols I know for a fact run higher than this, and last time I asked a petrol owner they said 100C or 105, can't remember but it sounds about right for a petrol.

Pistratoaie

Yes it's an auto, when I first started having these issues, I considered thermostat, coolant sensor and oil cooler to be the culprits. Oil cooler being the last and remaining one to check off, it seems to be coming down to that.

I would be happy to reach anywhere above 90 at this stage, haven't seen mine go above 100 at all, and it is a petrol... weather here is never below 0, so should reach temps pretty easily; but it's not
Ahh, back to looking at oil coolers I guess

kobolt60

It will be realy interesting to see if the fan switch replacement works for you, Ive located mine and it does not seem that hard to get to. I have in the past sprayed some electrical cleaner on everything but no result and also inspect visualy and by hand checking for bad cables but no... Thanks for the link btw.

When im doing 60 mph (80.47 km/h) its pending 76-84 degC.....

I noticed today that when just starting it up and idle towards operation temp it will like go up to 92 degC and then, what I belive, the stat just open and drops it to 80s....

Oil cooler I been reading about in some other forum..well at least its the most easy part to get to...wonder if open it and clean it could resolve the problem. If the stats are on the oil side perhaaps they can stick as the vanos for example...

This is like taking too much energy from me.. hehe..but I never give up!

Pistratoaie

Hehe, I'm like you, I've been told to just live with it since it's not a big deal, but I'm not happy until I know it's all working properly! btw 60mph is 90kmh.

Yeah oil cooler is luckily easy to do, I'm just not sure why that affects reading by coolant sensor... so maybe replacing that sensor might resolve it. Have to wait and see.

kobolt60

Yes it should have been 90 ofcours.

I shall try to find a used oil heat exchanger cheap and make a test...

What I understand the oil cooler stuck open let hot water enter the top of the radiator and make the fan switch believe stat needs to open...it does but not for the correct reason....

I do not know.....dam

Pistratoaie

So after Monday and Tuesday testing by mechanic, found one sensor to be giving different reading to coolant sensor. So we've replaced that sensor (I don't know anything about it), thermostat again with another BEHR one, and fan switch I believe.

So the temperature readings are confirmed to be accurate, but still no change in circumstances. Engine climbs to 92 when stopped in traffic and thereabouts in slow traffic. accelerating and cruising above 40ish (km/h), temperature plummets to 75 and remains there...

Of course, cabin heat drops above 70km, which might make sense since engine temperature is at 75 at this speed. Heat runs properly when stopped because engine temp rises to optimal range.

Well I'm out of ideas now, anybody got any ideas/recommendations?

twh

Just throwing out some thoughts...

Have you found anything from BMW that shows what the cooling profile is? Like at idle, cruising, allowable temperature ranges, etc.

(1) Have you checked to make sure the water pump is not running all the time? That is, could it be that there is a permanent signal telling the water pump to run?

(2) If not (1), perhaps the engine computer is telling the water pump to run constantly or more than necessary while you are in motion. Checking this would require tapping into the water pump wiring harness someplace.

twh

I'm looking at the Bentley manual...

(3) The thermostat is also controlled by the engine computer.

Quoting from Bentley, "the engine control module activates the thermostat to maintain the engine coolant temperature within a narrow range. If the electronics fail, the mechanical function of the thermostat acts as a fail-safe".

So, it could also be possible the thermostat is somehow being held open as my (1) and (2) above. That is, a permanent short in the control to the thermostat or some erroneous signal while the car is moving.

Pistratoaie

Thanks for the input twh. I'll be checking on those things at the end of the week with tech. Plus getting software updated as another step to try out. I'm wondering whether your 3 point is closest to plausible; but what really doesn't match is that there would surely be an error code if water pump wasn't working properly... right? Thanks again, will post back