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hey guys , just finished 50k servise yesterday . my friend works as a mechanic in one of the indy shops in chicago and he helped me with the job. everything took about 8 hrs to complete including 2 hrs of trying to get the thermostat gasket out of the housinggrrrrrrr.
new parts: serpentine belt, ac belt, fuel filter, micro filters,air filters,ngk sparkplugs, thermostat, gasket, bmw coolant, bmw oil, oil filter and new fan clutch.

now my thermostat was replaced about a year ago and i always thought it was running opened because only on hot days would the temp gague reach mid marker. computer never threw any codes.when cold outside it would always be like 2 milimeters on the cold side. i always thought the new thermostat would fix this. i was wrong ...i even made sure to buy original bmw one because there was some talks how the generic ones are a bit differend. well new coolant, new thermostat and a gasket and my car still runs the same . when cold it never reaches the middle on the gauge.
2nd my fan clutch was working fine but after a bmw mechanic suggested me to change it because while changing my oil the last time i was at the dealer he said that if the car is all wormed up you shouldn't be able to stop the clutch with your hand...he said mine was going bad and i should change it.....well i did last night and guess what....it still does the same thing...2nd part i replaced for nothing!!! i am so pissed off !

the only thing i am really happy i replaced was the spark plugs and the fuel filter ..boy when i drained the fuel out of the old one it was black! and the stealer claims it's life time filter...yeah right.
anyway just thought of sharing my exp. with you guys and see if anyone else replaced thermostat and saw no results....should i look into something else?i mean if it was the temp sensor there would be no variations in temp at all right? my oil temp seems to be fine (about 175 180 when driving normal to 200 dregrees when driving hard). no codes at all when driving. is it possible my temp gauge on the cluster is set like that? on my old m3 temp would always be in the middle no matter if the temp outside was -10 or 90, is this normal for m5?

any suggestions would be much appreciated
 

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Based on the recent behavior of my coolant temp gauge I thought the thermostat was the culprit and replaced it...didn't solve the problem of low readings and replaced the temp sensor next. Voila, problem solved, now the gauge needle is always vertical.
 

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my coolant temp gauge has always been a bit to the left of center on a cool day, gets right to the middle on a warm day. My oil temps generally run a hair under 210 when it's cool, at or a little over when it's warm.
Sounds normal. Do a search for "unlocking the obc" and you can monitor real time temps on the instrument display below the speedo/tach. Coolant temps should always be >79C when the car is warmed up. If you're seeing less than that either the thermostat isn't closing or the sender is bad.
 

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there are 2 diff. temp sensors...one that mounts on the lower radiator hose or the one for fuel injection and temp gauge. one is Part # : 13 62 1 433 077 and the other one is Part # : 13 62 1 703 993 . which one should i replace you think? ...or both just in case?...will i need to drain the coolant for this?

thanks for your input on this
 

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Until you see something abnormal on the OBC a la mottati, or can tell us that it takes way too long to get the gauge to mid-range, put me in the camp of people who think neither the old nor new thermostat was/is malfunctioning. Love hearing about DIY'ers, though. Kudos.
 

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Adding to others, I wouldnt trust the dash guage to diagnose a thermostat. You need to verify with the OBC. Also, as I understand the gauge is buffered to only show large changes in temperature. It is not a true guage like the older BMW's...one step better than an idiot light.
 

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my feeling is people jump the gun and forget about basics the temp sensor is alot eaiser and cheeper to change and see that fixed the problem. if not no biggie then go for thermostat
 

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My coolant runs to the left of straight up in winter and striaght up in summer. Same goes for oil temp. Ambient temps have to 75-80 to get the gauges to be straight up. The M5 is different than any of the other BMWs I have owned (which operate just like emccallum stated).
 

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Kudos for the DIY. If you do a search, you'll see that it's quite common for these cars to have the coolant gauge read on the cool side.

Michael
 

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Thermostat housing is known to fail on many BMW V8's. When the M60 3.5 got upgraded 11hp, they changed the lid from plastic to alloy. Not for show!
 
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