Overheating (according to gauge) minutes after starting - KV6

[ashy90]

I am trying to diagnose the issues my 2002 ZT V6 has.

The temperature gauge goes above half way when the engine has been running for just a few minutes.

There is hot air from heaters.
Coolant and oil look good.

If the engine is started with the expansion tank cap off, the coolant level rises almost immediately and will overflow.

I have tried bleeding air out. With the engine off, coolant flows nicely out of the bleed screw hole. When the engine is started, coolant pretty much stops flowing out of the bleed screw hole (but level in tank will rise).

What are peoples thoughts?