2009 X5 35D ---91000 kms
So finally changed both main thermostat and transmission thermostat.And also cleaned the carbon out from the intake manifold and head intake ports as sgrice described in his DIY.
Now engine temp stays 85~86 deg C while idling and 87~88 while driving even the ambient temp is just 7 deg and before it was staying 70~75 degrees!!!
Now my question is about bleeding the air out of the cooling system.I think i put back approx same amount of coolant that i drained out before opening up the thermostat.So after finishing the job, i just filled the expansion tank with coolant and i ran the cabin fan at max high heat settings to start the aux water pump and then i started the engine and went for drive.I was watching coolant temp with bmwhat app and it stayed at around 56~57 degrees for first 7-8 mins of driving.My concern is that is it possible that in that period of time ,engine block and head was running dry? because coolant temp sensor was not hitting coolant and that's why it was showing just 56~57 deg until thermostat opened and coolant started to circulate and temp rose to 86~88 degrees.But even after the temp got stabilized and coolant started circulating, expansion tank didn't take much coolant.I would say just 100-200ml.
Do you guys think if there is any chances of heat damage to the cylinder liners and head in first 8-9 mins of running due to air pocket in the system?