My car thinks it's overheating for 30 seconds every cold start then goes back to normal
Got a really weird one with my 2018 530i that's been happening for about three weeks now, every single morning when I start the car the iDrive throws up a yellow overheating warning and the temp gauge spikes toward the red for maybe half a minute before slowly settling back down to dead centre like nothing happened and staying there perfectly for the rest of the drive no matter how long I'm in traffic. Coolant level is fine, no visible leaks on the garage floor, the electric fan isn't running constantly like it's trying to compensate for anything, and the actual engine temperature feels completely normal when I check under the hood. Part of me wonders if it's just a faulty coolant temperature sensor sending a dodgy reading when the engine is still cold, but the other part of me is terrified it could be an air pocket or the early stages of a head gasket issue that's pushing combustion gases into the cooling system. I've been searching for a BMW Garage that can do a proper cooling system pressure test and maybe a combustion leak test on the expansion tank rather than just scanning for codes and shrugging, because the intermittent nature of it makes me think a generic OBD scan won't catch anything useful. Anyone dealt with a similar false overheating scare and had it turn out to be something simple like the sensor or a thermostat that was sticking briefly.
