30th December 2011, 04:47
Member, P500, DSC On (>600)
Join Date: Nov 2010
Location: Pendleton, NY
2000 M5 Anthracite
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The needle is suppose to be just left of center, or to be less exact - higher than the 1/3 mark, lower than the half way point. If you are questioning whether the car is running cold or not, disregard the gauge altogether and use the OBC secret menu to watch the temps. Anything below 78-79 at highway speeds is too low. What I have found, with my person experience, is that when the temp is only reading slightly low (77-78 all the time while driving) the thermostat is probably fine, but that inner seal that most people say you don't need to replace - needs to be replaced. The gasket part of that seal gets too hard and stays deformed in a position which allows extra coolant to flow past the thermostat body before you want it to... thus creating an over cooling situation.
Edit: Make sure you drive a good 10 minutes or more before you compare the OBC to the gauge. I have found that when the OBC first gets up to temp (79) the gauge will still be at the 1/3 mark. After a while longer the needle slowly moves up further, but the OBC temp will stay the same, or maybe hit 80.
Last edited by technician117; 30th December 2011 at 04:49.