[Efthreeoh]

Originally Posted by kkasson

Has the Z4 ever overheated on you? I'm curious what the gauge did if so...I'm assuming that the gauge is buffered like it was on the E46. Did you have much time to react?

The E46 gauge wasn't super helpful because by the time it started to move the engine was basically overheating already. The N52 runs hotter than the M54 under normal conditions, so I think that having a coolant gauge would be even less useful. That's my best guess as to why there isn't one on the E90...it just wouldn't really be any more helpful than the warning light.

Seriously dude are you trying to jinx me!?! No the Z4 has not yet lost it's pump. I'm sure it will peg the needle like any car would when it overheats.

Again I'll suggest that the E90 doesn't have a water temp gauge merely because of real estate issues. The gauge cluster in the E90 is small relative to past BMW 3-series designs, which I think is the result of incorporating the I-drive screen into the dashboard. Additionally, I'm sure the engineers were of the mind that a water temp gauge was not necessary given the level of cooling system control that most modern cars have. IMO I think it is the opposite of what you guys are speculating about the variation of engine temperature. I think with the use of an electric variable-speed water pump and an electronically controlled thermostat, the engine temperature can be actually more precisely controlled.

[chris7520]

You can read the actual water temp in the test mode. N52 runs at around 200-220 F. if your in sport or manual and pushing the car it will drop to around 180 or lower at times. I've heard that the reason there is no actual dash gauge is that since the temp varies so much depending on what you are doing. that they didn't want to freak out owners with the gauge moving that much so the Z4 that has gauge only moves if things are really wrong. you can take that last bit with a grain of salt because I can't confirm that with BMW

[Three_thirty_I]

Originally Posted by chris7520

You can read the actual water temp in the test mode. N52 runs at around 200-220 F. if your in sport or manual and pushing the car it will drop to around 180 or lower at times. I've heard that the reason there is no actual dash gauge is that since the temp varies so much depending on what you are doing. that they didn't want to freak out owners with the gauge moving that much so the Z4 that has gauge only moves if things are really wrong. you can take that last bit with a grain of salt because I can't confirm that with BMW

Even the older M54 motors from the E46 had a similar temperature management like this, push the car harder and the coolant temps comes down, yet they have a temperature gauge, so it's not that, and as mentioned on the previous page, some E90 models, the E92 for instance, do have a temperature gauge in place of the econometer. So it's literally down to BMW deciding if it's important for us to have a temperature gauge or not - clearly not. And BMW is not the only car maker that uses mapped temperature controls, and I doubt that all of those other cars don't have temperature gauges. Therefore, the "middle" reading is simply covering the min and max range of temperatures based on typical operating temperatures, it's only outside of these readings that it would then fluctuate.

[Meeni]

The car actively works to get the temperature in the 95-98(c) as it is the most efficient for fuel consumption.

If you plug-in the INPA diagnostic computer, you can track what the DME does with the electric water pump and the thermostat. It will close the thermostat at lower temperature to make it raise, and it will turn on fan and ramp-up the pump speed when it reaches 98 to return to 95. The water temperature is almost constant whatever the external condition or load.