the E38 uses an electronicly controled thermostat. it is not oporated by the use of a wax thermostatic element. and just for the record, putting an old fashioned thermostat in boiling water still does not tell you if it opens at the correct temperature. water not under pressure boils at 212 degree F. most modern thermostats are supposed to open at 182-190 degrees F. if it is opening after the correct temperature, like in depressurized conditions in a pot, thats not telling you the correct opening point. also the pot would radiate heat into the thermostat, and again is not correctly telling you anything. possibly would do more damage that way too.
sometimes a bad thermostat on BMWs will show a engine code, possibly and engine light will come on too. but not always. to test the thermostat on your E38 properly, you would need to use a scanner tool that connects under the hood. they are expensive though. the OBDII port in the car will not tell you about a faulty thermostat, just basic things, sensors and whatnot.
color: anthrecite metallic
wheels: style 89 E66, 19X9F 19X10R
ext. lighting: 8000k D2S & LED plate light
*want to get sport rear diff*