Brake fluid if leaking from the port on top of the master cylinder.
Front left caliper was dragging. Replaced the caliper and the master cylinder but brake fluid is leaking from the port on top of the mc. The original mc had silicone plugging the port.
Any suggestions as to what would cause it?

 

I've never seen fluid come from there. As far as I understood, that is a sealed port. Sealed by press fitting a ball bearing into the port. If it is leaking, I believe it's a manufacturing error if new.