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The Arkleyologist
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Discussion Starter #1 (Edited)
This query is a spinoff from my previous post. I recently installed a new 92*C (197*F) thermostat into my Z3. After installing, my obd reader said I was consistanly running at 213.8*F. (My obd reader was consistant with the repair shops more sophisticated reader) I then installed an 88*C (190*F) thermostat. I am now running at 202*F as measured by my reader.
My question to the group (who have an obd reader) is this: Are your actual obd readings consistant with the value stamped on your thermostat?
 

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Warning - Thin Air
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Isn't the thermostat temperature the temperature at which the thermostat opens, not the operating temperature of the water in the system?

Also, 92C is 197.6F, not 97F and 88C is 190.4F.
 

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The Arkleyologist
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Discussion Starter #3 (Edited)
Thanks for pointing out my typing/brain error on the temps...I made the corrections..I have owned over thirty British sports cars, all of them registered on the water temp gauge within a degree or two of the value stamped on the thermostat..not sure I understand your point.
 

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Thanks for pointing out my typing/brain error on the temps...I made the corrections..I have owned over thirty British sports cars, all of them registered on the water temp gauge within a degree or two of the value stamped on the thermostat..not sure I understand your point.
You put in a 92C thermostat. It will open when the water (coolant) reaches 92C, but that does not stop the water from getting hotter. The thermostat stays closed when you first start your car in order to help the water get hot quicker. Once it reaches the design temperature (say 92C) then the thermostat will open. After that the water will keep getting hotter until it gets to the design operating temperature of your car (if everything is working properly) then it will stay near to that temperature. You may see the temperature go up a bit with hard driving, but your thermostat will stay open until the water temperature goes below 92C. But that shouldn't happen until you shut off your car for some period of time. I hope this explanation is understandable.
 

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The Arkleyologist
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Discussion Starter #5
Thanks khammack...given that explanation, what are others seeing as compared with my experience? Again...only those that have ancillary obd water temperature measurments need paticipate..
 

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A friend of mine had a water pump issue and was using an OBDII reader to keep track of his coolant temp. He was tracking how much hotter his coolant was getting above his normal temp so that he could limp home without over heating his engine. He was looking at 203F as his normal temp.

Here is a good description, from Blacklane, of the check points the car uses - https://www.bimmerfest.com/forums/showpost.php?p=7792427&postcount=4
 

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The Arkleyologist
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588 Posts
Discussion Starter #7
That is a great explanation from blacklane..(met him once..only lives @ 25 miles from me!) Gives me peace of mind after reading his post...my car with a 92*C thermostat was running consistanly at 213.8F and occasionally reaching 220*F. Guess that was unecessarily worrying me...now running 88*C thermostat and running consistantly @ 202*F. Thanks for the information khammack! Would still like to hear from others about their experiences...
Cheers
 

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This subject has bothered me for a long time because I don't understand why everyone thinks a colder engine is better. Heat is good when it comes to complete combustion, the hotter the cylinder the easier fuel will vaporize. A cold engine is a less efficient engine, basically I'm trying to understand why would the manufacture use a certain thermostat if it was harmful to the engine? This excludes extreme climates and racing applications.
 

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The Arkleyologist
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Discussion Starter #9
Aboismenu...just call me paranoid I guess...thoroughly agree with your logic...my problem is with the many horror stories on this thread about engines so quickly overheating and destroying the aluminum head..I am simply trying to do all I can to avoid that. I am now running the 88*C thermostat and am very happy with it as I seldom ever go over 202*F. I have owned five Z3's and the one I have now has zero rear differential noise (the other 4 had this issue to one degree or another). I want to do all I can to make sure I keep this car on the road as long as possible. Once I internalized the notion that the coolant temp is relative to where the measurement is taken, I feel much better about the entire situation.
 
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