M5 Thermostat - The Unofficial BMW M5 Messageboard (m5board.com)

raland9 · 11th June 2001, 01:55

Since I am convinced the M5 runs far better in cold weather or at least when the car operates with a water temp gauge less than at 12:00, and since I have had great luck in getting 745's to run better with lower temperatures, I would like to try a lower temp thermostat. I simply can not find one over here and wonder if anyone from the message board might check in Europe for availability. The current one is 79 deg. celcius and I would like to use a 71 deg. thermostat. In the 745, I first tried a 75 deg thermostat before settling on a 71 degree unit (OEM was 80 deg. cel). I'll be the "guinea pig" and try it. I wonder if Nowack uses a lower temp unit.

Rick

greg · 11th June 2001, 04:45

Just an educated guess here, but the water temp should make very little difference in the way the engine runs. The outside air temp is a MUCH larger factor, because it determines how much oxygen is available to be mixed with gas in the cylinder for otimum combustion. Hot, humid air simply has way less oxygen per unit volume than dry cold air.

raland9 · 11th June 2001, 05:49

You're right in part, but I have less control over the air temp. This one is easy and on other cars, it seems to work. Remember, our air temp (particularly in Texas) is far warmer than in Germany (typically) so on these other cars, BMW even offered sub-tropical radiators to lower water temp.

Rick