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E90/E91/E92/E93 (2006 - 2013)
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  #1  
Old 02-02-2007, 06:48 AM
jelliotlevy jelliotlevy is offline
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How do our E90/E92 thermostats work?

I am on another tear to figure out how the sophisticated subsystems in our Bimmers work. I first checked out How Stuff Works:

http://auto.howstuffworks.com/question248.htm


That link describes the conventional wax thermostat, which has appeared in most of the cars I have owned, including my original, and much beloved (for sentimental reasons only) 1953 DeSoto. I am not sure how many 2006/7 model cars still use that old approach, but I seem to recall reading somewhere that our thermostats are electrically controlled. I can certainly imagine a combination of temperature sensor, actuator motor or solenoid and movable valve working in concert. To be candid, that is merely a guess, and Idon't really know how our Bimmers do it - and How Stuff Works seems to have let me down.

Surely, someone in this august and supremely knowledgable Bimmerfest group knows the real answer, and will lead us to it. Please do not respond in this thread unless you are august and supremely knowledgeable.
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  #2  
Old 02-03-2007, 03:57 AM
killcrap killcrap is offline
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i am only modestly knowledgeable.

the n52 thermostat and water pump are 1 unit. the water pump is fully electronic and not driven by a belt. the thermostat is conventional mechanical. when the coolant temp is high enough, the dme will activate the electrial porition of the thermostat to open the thermostat further.
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  #3  
Old 02-03-2007, 06:28 AM
jelliotlevy jelliotlevy is offline
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And I am old enough to remember those days when you could, for a couple of bucks, buy a thermostat, a gasket and a small bottle of gasket goo, and change the thermostat yourself with about 10 minutes of labor. Of course I also remember my 1964 SAAB, which came with two thermostats: one red and one green. The thermostat went in line in a primary hose. You had to undo two clamps, insert the proper thermostat (165 degrees, green, in the summer; 180 degrees, red, in the winter) and re-fasten the clamps.

Having the water pump in a non rotating mode during warmup must certainly speed up that process. Changing an E90/E92 thermostat is most likely a job for those high priced auto surgeons in their white coats.
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Old 02-03-2007, 07:24 AM
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move.over move.over is offline
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Quote:
Originally Posted by jelliotlevy View Post
And I am old enough to remember those days when you could, for a couple of bucks, buy a thermostat, a gasket and a small bottle of gasket goo, and change the thermostat yourself with about 10 minutes of labor. Of course I also remember my 1964 SAAB, which came with two thermostats: one red and one green. The thermostat went in line in a primary hose. You had to undo two clamps, insert the proper thermostat (165 degrees, green, in the summer; 180 degrees, red, in the winter) and re-fasten the clamps.

Having the water pump in a non rotating mode during warmup must certainly speed up that process. Changing an E90/E92 thermostat is most likely a job for those high priced auto surgeons in their white coats.
Here is interesting thread http://forums.vwvortex.com/zerothread?id=2993477 on how to change a electronically controlled thermostat.
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  #5  
Old 02-03-2007, 08:23 AM
jmonier jmonier is offline
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Quote:
Originally Posted by killcrap View Post
i am only modestly knowledgeable.

the n52 thermostat and water pump are 1 unit. the water pump is fully electronic and not driven by a belt. the thermostat is conventional mechanical. when the coolant temp is high enough, the dme will activate the electrial porition of the thermostat to open the thermostat further.
The electric coolant pump is actually controlled to adjust the engine temperature. It doesn't even run until the engine is warmed up. Under these conditions I'm not even sure that there is need for a thermostat.
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  #6  
Old 02-03-2007, 10:19 AM
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spots spots is offline
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Originally Posted by jmonier View Post
The electric coolant pump is actually controlled to adjust the engine temperature. It doesn't even run until the engine is warmed up. Under these conditions I'm not even sure that there is need for a thermostat.
That would be my view on it as I believe they would duty cycle the pump to achieve the desired thermostatic effect.
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  #7  
Old 02-03-2007, 12:16 PM
jelliotlevy jelliotlevy is offline
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Quote:
Originally Posted by move.over View Post
Here is interesting thread http://forums.vwvortex.com/zerothread?id=2993477 on how to change a electronically controlled thermostat.
.......

That thread makes scary reading. I am sure everybody knows that the VW Phaeton and its incredibly expensive and complicated W12 engine no longer can be bought in the USA. Quite an operation to change that thermostat, and the part apparently costs about $400. That Phaeton was VW's notoriously unsuccessful attempt to compete with Mercedes high end.
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  #8  
Old 02-03-2007, 01:39 PM
jmonier jmonier is offline
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Quote:
Originally Posted by spots View Post
That would be my view on it as I believe they would duty cycle the pump to achieve the desired thermostatic effect.
There's a lot of info in the documents in this thread:

http://www.e90post.com/forums/showthread.php?t=38856

They actually adjust the head temperature in four different increments according to how hard you're driving.
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