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Discussion Starter · #1 ·
Greetings,


Roughly 10 months ago, I've put in a new thermostat for my M54B22, since then, whenever I was monitoring the coolant temperature using the OBC hidden menu function 7.0, the temperature (after the car was already fully warmed up) never goes beyond 90°C, even under heavy load, and if it drops, it rarely drops more (if even) a couple of degrees. The temperature stays almost too perfectly at 90°C, sometimes, I think something might be wrong :LOL: - part of the reason I'm making this post. So, out of curiosity, what are your coolant temperatures like and how do they change?

Also, what would be the best coolant operating temperature?
 

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Е46 sedan M52B20TU 1999
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M52B20TU 102 C at idle, but when driving it drops to 96-98 C. I thin the problem is with the thermostat. I would be happy if I were you, because even 96-98 C is too high and negatively affects the plastic under the hood and rubber seals. My advice to you is to add a mod for the coolant temperature gauge so that you do not miss the momen the temperature suddenly starts to rise.
Gauge Font Circle Measuring instrument Number
 

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Discussion Starter · #6 ·
M52B20TU 102 C at idle, but when driving it drops to 96-98 C. I thin the problem is with the thermostat. I would be happy if I were you, because even 96-98 C is too high and negatively affects the plastic under the hood and rubber seals. My advice to you is to add a mod for the coolant temperature gauge so that you do not miss the momen the temperature suddenly starts to rise.
View attachment 965940
Actually, the last couple of days I've been playing around with the gauge settings for that exact reason.

I'm trying to make the red light at the top end of the gauge to turn on based on the settings.

So far I've been unable to trigger it, I know the light is functional as it turns on during a cluster test, but it somehow always stays off even when I make the needle go heavily into the red during test...maybe the light gets triggered based on a completely different setting/logic/input (and not based on the temp gauge relative needle position).
 

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2013 X1 M-sport
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I'm trying to make the red light at the top end of the gauge to turn on based on the settings.
Read this post.
 

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Discussion Starter · #9 ·
Read this post.
Thanks for the link, but I've read the whole thread probably 4 times so far, that is why I'm "playing around" with the settings 😆
 

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2005 330xi Auto, 2006 330ci Vert Auto
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Got maybe a hint what could be possible causes?🤔
I would have to guess it's the thermostat. I have seen thermostats that open at different temperatures even from the same manufacturers. You can remove the thermostat and place it in a pot of boiling water on the stove and monitor when it opens with a kitchen thermometer in the water.
 

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Discussion Starter · #16 ·
Mine's standing steady at ~90 celsius these days. usually ~95c when the weather is warmer.
Which thermostat do you have?

Mine is a Mahle one and now in colder weather, it sits at 90°C (didn't really pay attention to coolant temperatures during summer as the gauge needle was always perfectly in the middle)...any chance yours is Mahle too?

I've found some thermostat reviews, and there are people saying the Mahle thermostat opening lower than other manufacturers...
 

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Discussion Starter · #17 ·
It will be hard to tell if it regulates at 90C, or 93C which is normal
Haven't tried the stove experiment but I guess it would be still hard to tell.

To really make most of such an experiment, one should very slowly, degree by degree increase the temp., hold that temp. for a long enough time and make notes of any observable changes...

You are more likely to sweep over a temperature range in a shorter time period during the experiment which will make it a lot harder to draw strong and concrete conclusions about what exactly happens at which single temperature point rather than range.

I highly doubt that the thermostat opens instantaneously when it reaches a certain temperature, therefore, a very gradual temperature change would be the most revealing into the workings of the thermostat. That is something I can't currently replicate in my kitchen.

I might be wrong in my assessment though.
 

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I highly doubt that the thermostat opens instantaneously when it reaches a certain temperature, therefore, a very gradual temperature change would be the most revealing into the workings of the thermostat. That is something I can't currently replicate in my kitchen.
It opens gradually as temp increased, and so it is very hard to tell if yours will regulate at 90C or 93C by watching it alone. It might show the slightly difference when cooking a known 93C side by side with yours, but I still think it's hard to tell.
 

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2000 320Ci 2.2 vert MT
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mine is around 97, but flows between 89 in highways and 102/103 in heavy loads when thermostat opens and goes back 89.
Original thermostat, temperate climate (Italy)
 
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