its not connected to the radiator
it is not needed for operation of the car
it can be removed
it DOES improve startup by enriching the air intake vapors
it DOES present serious problems of vacuum leakage with age (sounds like what you have is a large vacuum leak)
the tube connected to the valve goes directly to the throttle body, the other side of the valve is connected to the canister, and the other tube from the canister goes to the gas tank.
the canister also has a drain cap on the end, so if the valve is stuck, you have a bad intake leak. you can remove the vacuum hose end from the valve and plug it up. that should solve your problem in the immediate while you determine the course of action, which is:
A: ditch the whole thing.
B: get new valve and canister and fix it.