[pdude1]

Recently changed the water pump and thermostat. When I bled the coolant it ran for about 9 minutes before I was out of battery. Drove for 2 days limited driving.

I now put a charger on it and trying to re-do the bleeding and I don't ever hear the pump turning on/off. At least not how it did earlier. Is it smart enough to know maybe it's already bled? Or is something wrong?

[Efthreeoh]

If you ran it, it's bled.

[pdude1]

wasn't sure if was done since I lost power at around 9 minutes (heard 12 min).....so maybe it was done and shut off before my 335i ran out of battery...wasn't sure if the process got hosed. I'll assume it was good then!

[Efthreeoh]

The purpose of bleeding is to get air trapped in the head out of the cooling system. The small diameter line that goes from the upper radiator hose over to the reservoir tank is in the system to give a pathway for the air to separate from the coolant flow and go back to the reservoir where it will bleed out through the cap vent. After 9 minutes the air should have bled from the head. After you ran the engine to temperature the air definitely is out of the cylinderhead.

The cooling system acts just like a bottle of water, the air is always on top of the water. The highest point in the cooling system is the top of the reservoir. The highest point in the engine is the cylinderhead, so that is where the air gets trapped when refilling the system. The bleed process moves the air out of the head and into the reservoir.