adjust the floating bulb, it may be running over the top of the overflow pipe
because whatever is on the other end of that overflow pipe is overflowing
The overflow tank is either cracked or its overheating and leaking from the cap
Depends on the design - it could be over-loaded due to high RH, it could be defrosting, it could have a full condensate reservoir.
Yes, the gasket between the overflow pipe and the tub can go bad, or it can leak around where the pipe is attached to the drain.
The alternator oil pipe on combo van leaking does feed the vacuum and the return pipe.
Extend the overflow pipe underground to a point where it is above ground.
from your overflow valve
You may have a bad radiator cap.
bad radiator cap
Depends on what type of overflow and what it services and whether it is constantly happening or intermittent.
It does not necessarily indicate a problem. If the cooling system was over filled while cold, the excess will have to escape from the overflow when the pressure builds. This is normal. If it continues after several periods of the engine warming up, it may mean that the cap is defective.