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E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.


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Old Mon, Apr-22-2019, 01:13:02 PM   #1
tedavis01
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Default Conflicting data over cooling problem

Hi Folks,

I have a strange cooling issue that seems as though some people have experienced before. I have a 2005 e46 m3 conv. with 75k miles

Data
Oil temp - The issue that was first noticed was a low oil temp gauge usually between the first dot and 210. The temp will hit 210 if in traffic but not on the highway. The oil used to hit 210 or very close and not really move much now it is fluctuating between the first dot and 210.

Coolant temp gauge - As i did more research i started noticing some other issues - the coolant temp gauge would move a couple of mm to the cold side from straight up - it would get nowhere close to the first hash mark though. I took OBC readings during a drive and the coolant stayed between 80 - 84 C degrees which coincided fairly close to what the oil temp was.

Aux fan - I also noticed that the Aux fan was also on after a 20 minute drive which was strange to me since I did not have the AC on and the outside temp at the time was at 70F.

Main fan - I checked the fan clutch when the car was cold and there was some resistance but not sure how much there should be to know if it was gone.

Car does not have any codes or lights on the dash. All clear.

Causes:
1. Thermostat
2. oil temp gauge
3. fan clutch
4. aux fan temp sensor/switch

Where I am confused is if it was the thermostat why is the aux fan on? A soft fail on the thermostat would explain the slight coolant needle movement and oil temps. I am nearly eliminating a bad oil temp sensor because the coolant temp matched the oil temp. I am assuming that if the fan clutch was bad i would get additional cooling from the main fan but the thermostat would close which would increase the temp. Also, i am not sure how much cooling the aux fan contributes.

The best I can come up with is that I have may have a soft fail on the thermostat and a bad aux fan switch.

I guess i am looking for some feedback. In reviewing the forums it would seem that all of these are potential causes from looking at what other people experienced. I am trying to get to the root cause of the problem as i dont want to just start replacing things since I can go to the stealership for that.

thanks for the input,

Tim
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Old Mon, Apr-22-2019, 03:09:54 PM   #2
Kenny167
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Default Re: Conflicting data over cooling problem

I'm really not sure what the issue is here, this all sounds completely normal minus the oil temp fluctuating. The aux fan turns on if it needs to, it's possible that your fan clutch is wearing out so the aux fan is being used to compensate. But since you have no overheating and no codes, I see nothing to worry about here.
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Discussing Conflicting data over cooling problem in the E46 M3 (2001-2006) Forum - Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)