My 04 base mini is constantly overheating. This morning I had codes P0128 and P0117. I swapped out the Thermostat, and Coolant Temp sensor and the car continues to overheat with them minutes of starting it. When I bought car I replaced I replaced the PS cooling fan? Amateur YouTube mechanic, what else could be causing the over heating?

 

If it's overheating just a few minutes after starting it makes me think the head gasket is blown.

 

You should also check the flow of coolant in the radiator. It's possible that the radiator itself is clogged. Might try a coolant flush product from AutoZone, O'Reilly's, etc. It's also easy to install the thermostat backwards (spring side goes inside the block - see illustration below). If that's the case it will not open/close properly.