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E46 (1999 - 2006)
The fourth generation 3 Series (E46 chassis) was introduced in 1999 and set the standard for engineering and performance during it's years of production including being named to Car & Driver's 10 best list every one of those years! ! -- View the E46 Wiki

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Old 05-03-2015, 08:42 PM
alcian18 alcian18 is offline
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Location: seattle
Join Date: May 2015
Posts: 3
Mein Auto: 2002 325ci
New member, long time reader-first question regarding thermostat wide open

Hi everyone,

I love coming to this website for the plethora of information that it contains! I really appreciate all the hard work that everyone has done, as well as taking the time to post it. It really helps people like me when deciding to do it yourself!

I know there is a ton of threads regarding the thermostat being wide open. But I feel that my car doesn't fit the same symptoms. My car is a 2002 325ci (193,300 miles) and I've had bmw look at it twice, the first was last year, and again this year in march. Both times they have said my thermostat is stuck open. When I have read other threads regarding this issue the symptoms seem to always include slow to heat up, inconsistent temperature of the engine etc. The only reason that I found out my thermostat was open was when my AC started going out, I took it to BMW to get it recharged. My heat takes about 5 min to get hot, and my engine temp is directly in the middle of hot and cold never wavers. AC is the only thing that isn't consistent, I don't use it often since I live in seattle but it can work and then go out (where it's no longer AC air). Does my thermostat being open consistent with what I'm seeing? should I still plan on replacing it?

Also as another side question does anyone know what the average life expectancy of the engine? Lower bearings have been replaced, it just started burning oil but I haven't tried switching to 0W-40 as has been recommended on here to see if that stops the oil from burning.

Thanks for the help!
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Old 05-03-2015, 09:07 PM
forzam forzam is offline
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Location: east coast
Join Date: Mar 2007
Posts: 449
Mein Auto: 04 325Ci
The temp gauge will be in the middle position between 75 and 115 celsius, so it's basically worthless until you reprogram it. You can view the actual temp using obd or the onboard readout on the dash (secret menu).

I don't know if your tstat is stuck open, but if two different bmw techs tell you it is then..... Changing the thermostat can be done by you in about 10 minutes and should be done, along with the rest of the cooling system, as preventative maintenance.
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Old 05-03-2015, 09:31 PM
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bluebee bluebee is offline
Seek to understand,^Value
Location: San Jose, California
Join Date: Mar 2008
Posts: 24,226
Mein Auto: 02 BMW 525i M54 auto 130K
The first step in any debugging procedure is understanding how the system works, and fails.

To that end, this thread has a LOT of information that may be useful...
- How the thermostat works, including what the normal temperature of the coolant is when the thermostat opens under normal conditions (1)
Please read the suggested threads, where the best always add value to those threads, either by pictures or by descriptions, so the next person with the same problem stands on your shoulders.
See also: E39 Bestlinks & How to easily find what you need
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Old 05-03-2015, 09:38 PM
alcian18 alcian18 is offline
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Location: seattle
Join Date: May 2015
Posts: 3
Mein Auto: 2002 325ci
Thanks for the help, I'll look and see if the engine temp is normal. I'm worried about doing too much preventative maintenance that costs money if my car is going to crap out soon. I may get a new car soon, and if I do my boyfriend might take my car and sell his ford taurus. However do you think longevity in my car is feasible? or should he keep his car and I should sell mine?
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Old 05-04-2015, 02:32 AM
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jcjdavis1 jcjdavis1 is offline
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Location: Paisley Scotland
Join Date: Feb 2010
Posts: 218
Mein Auto: E46 1999 323i auto
Hi. I would swap the thermostat first then you will know the engine is running at the proper temp. Run the car with the CC on auto and see how things are, might be you need the aircon. re-gassed. If in doubt about keeping the car forget about all the preventative maintenance, just keep up with routine maintenance and go from there. Jim
The older I get the wrong bit gets stiff!!
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Old 05-04-2015, 03:18 PM
alcian18 alcian18 is offline
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Location: seattle
Join Date: May 2015
Posts: 3
Mein Auto: 2002 325ci
okay, I may do that since a thermostat online isn't too expensive! I'll also see what temp my engine is running at, because I am definitely curious. I may pass the car along (keep it in the family) so small fixes are doable. Not things where bmw charges me 500 for it.
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Old 05-05-2015, 08:12 AM
marcozandrini marcozandrini is offline
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Join Date: Feb 2014
Posts: 709
Mein Auto:
Search for "E46 hidden obc functions." Unlock the obc using the procedure. Then go to test 7: coolant temp. The obc will show a temp range of 95*C to 100*C with a properly operating thermostat. If the temp doesn't get above 90*C the thermostat needs to be replaced.
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Old 05-05-2015, 09:54 PM
GoForthFast GoForthFast is offline
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Location: New York
Join Date: Jul 2004
Posts: 2,768
Mein Auto: '04 330Ci 6-speed
Here you go
Attached Files
File Type: pdf OBC Hidden Functions.pdf (47.3 KB, 8 views)
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Old 05-06-2015, 05:01 AM
KiLisH KiLisH is offline
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Location: Africa
Join Date: Apr 2015
Posts: 8
Mein Auto: 3.28i
Smile Coolant indicator and temperature rise

Hi guys, this is my first post on bimmerfest. I have to say its been very helpful figuring out what's wrong with my 328i(2000). Coolant indicator shows and water comes out from the radiator cover. Thought my head gasket was worn out but after reading comments on this site, I changed the thermostat and BAM' problem solved. Thanks to u ALL!!
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ac, burning oil, thermostat

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