I have a 2008 BMW 528i (E60). Recently I had most of the coolant system replaced - water pump, thermostat, hoses, etc. The only things that were not replaced were the radiator and the coolant temperature sensor.

A couple times recently I got a high water temperature warning while driving. Both times I pulled over, waited about 10 minutes, restarted the car, and was able to continue driving with no further issues. My mechanic said it’s likely the water temperature sensor, so I bought one and plan to replace it myself.

I have two concerns:

1 - Torque on the sensor

From what I’ve read, the sensor is easy to damage if overtightened and it doesn’t require much torque. Some people say it basically just needs to be lightly snugged. Does anyone know the proper torque spec, or is “light snug” the correct approach here?

2 - Bleeding the coolant system

The procedures I’ve seen say to remove the expansion tank cap, turn the ignition on, and run the water pump with the engine off using a special procedure which is initiated by pumping the accelerator ten times

My concern is that this runs off the battery and can drain it. Many guides recommend using a battery charger or power supply during the procedure. I don’t have one, and I’m also worried my battery might be a bit weak.

Can I just run the engine for 10 minutes with the expansion tank cap off instead of using the battery-powered bleed procedure? Is there a reason BMW specifically recommends the electric pump method instead?

Thanks very much in advance for your help