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      10-19-2020, 01:32 PM   #1
itsrichierich
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Oil cooler thermostat stuck closed?

Hey folks, hope everyone had a good weekend!

So last week my bleed screw on the expansion tank started leaking and spat coolant everywhere. I think what might of happened was I stripped the screw when I was doing a coolant drain and refill before my road trip.

When this happened, I was about 10 minutes away from work. While I was driving, warning light came on saying my engine is running hot and that I need to drive very slow. Car went into limp mode actually because I lost a lot of power. I didn't have my coolant temp gauge displayed on my phone but I remember seeing my oil temp gauge (on the cluster) past the 250F mark.

I replaced the bleed screw and did the drain and refill process all over again and have done the bleed procedure about 5 or 6 times now to make sure I got everything out. But now I am starting to worry as I am wondering if it's a mental thing or if it's actually an error.

While driving, my bimmerlink app says my coolant temp is at 230F and oil temp is at 239F. Based on the info I have read, that is normal. But when putting the car into Sport+ mode, I remember these temperatures dropping. That's not the case anymore, not immediately at least. Prior to all this, I could of sworn my oil temp was running a little bit cooler than where it sits at currently. But again, that's why I question if it's actually an issue or just mental.

Am I wrong to think that the temp should drop pretty fast when in Sport+ mode? I am starting to think my oil cooler thermostat is stuck closed? Is there a way to test or diagnose that everything is working properly?

I have scanned the car with the BM3 and Bimmerlink app and no code is stored or present. Any comments or suggestions is greatly appreciated!
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      10-19-2020, 02:40 PM   #2
thejeremyman9
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From my experience going into sport/+ does not automatically or immediately lower the coolant target. It more depends on how you are driving. There's lots of times i go into sport/+ and i still see coolant around 230F and oil around 240F. At the same time, there are situations where i am just in comfort and i see coolant temp drop significantly - sometimes to low 200s, but i have seen as low as 185F. The latter was when it was 117F ambient temperature outside and i was just on the highway, coolant temps dropped significantly and oil temps followed. This was reported by another person when we had the huge heat wave in California not too long ago.

In summary my experience/observations is that the DME will adjust coolant target based on two main things - how you are driving (i.e., how you have been driving the last few miles, aggressively or not), and ambient temps outside. The more aggressive you are driving and the hotter it is outside, the lower the coolant targets. As far as i know the oil thermostat is mechanical so there is no way for the DME to control that, so the oil temp dropping with coolant is simply an artifact of the lower coolant temp in the engine (same as when you run a flash time cooling option). And also based on my experience, engaging sport/+ does not automatically lower coolant target, although i cannot confirm if there is any logic in the DME that might make it more readily lower coolant target in this mode compared to comfort.

If your oil cooler thermostat was stuck closed i think your oil temp would continue to rise if you were driving aggressively at all.
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      10-26-2020, 01:27 AM   #3
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Quote:
Originally Posted by thejeremyman9 View Post
From my experience going into sport/+ does not automatically or immediately lower the coolant target. It more depends on how you are driving. There's lots of times i go into sport/+ and i still see coolant around 230F and oil around 240F. At the same time, there are situations where i am just in comfort and i see coolant temp drop significantly - sometimes to low 200s, but i have seen as low as 185F. The latter was when it was 117F ambient temperature outside and i was just on the highway, coolant temps dropped significantly and oil temps followed. This was reported by another person when we had the huge heat wave in California not too long ago.

In summary my experience/observations is that the DME will adjust coolant target based on two main things - how you are driving (i.e., how you have been driving the last few miles, aggressively or not), and ambient temps outside. The more aggressive you are driving and the hotter it is outside, the lower the coolant targets. As far as i know the oil thermostat is mechanical so there is no way for the DME to control that, so the oil temp dropping with coolant is simply an artifact of the lower coolant temp in the engine (same as when you run a flash time cooling option). And also based on my experience, engaging sport/+ does not automatically lower coolant target, although i cannot confirm if there is any logic in the DME that might make it more readily lower coolant target in this mode compared to comfort.

If your oil cooler thermostat was stuck closed i think your oil temp would continue to rise if you were driving aggressively at all.
I will say that it ran cooler when it was hot out versus it running hot with the colder weather out. The good thing is, itís not getting past the 250F mark.
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      10-26-2020, 11:44 AM   #4
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Quote:
Originally Posted by itsrichierich View Post
I will say that it ran cooler when it was hot out versus it running hot with the colder weather out. The good thing is, itís not getting past the 250F mark.
Sounds completely normal then.
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