Car is over heating. Has been on computer -no codes showing anything wrong. The liquid flow has been tested as well as engine pressure. 2 different garages. Can't figure out what is wrong.

I think could be the thermostat,is stuck closed, as you don't have codes it's possible the sensor integrated in the thermostat has failed too, I had similar issue but my car engine was always cold, my thermostat was stuck open

It could be a thermostat, but usually, the car would throw a code over the thermostat. Then again, like the previous user said, the sensor in the thermostat could be bad as well. I would say the water pump, but if the coolant flow is okay, that's unlikely.

The BMW mechanic at the 3rd garage I've had it to said he can't figure it out either. Ugh! This is crazy. Water pump is good. Even checked the voltage and it's fine. Definitely not a cracked head or bad head gasket. This is soooo frustrating. Should I have him put a new thermostat on just in case?

Probably not a bad idea to replace the thermostat.

Thank you. I'll call the shop Monday and see if they will just do that and see if it fixes the problem.