What size tank are you talking about? But regardless of that, if propane is escaping when you turn the valve on, yes, there is something wrong with that valve! Get it serviced immediately for safety sake!
If you haven't already, next time put a bit of dish detergent in water and apply to the area where you suspect a leak. You will be able to tell easily where the leak is actually located.
It's a 20 pound grill tank. I turned it in for another and took the new one home, hooked it up and danged if I couldn't hear hissing when I began to fire up the grill. So I shut it off and waited, and then when I turned the valve back on I...