in my experience water pumps fail a bit and leak out of weep hole and progressively the bearing gets worse.
my wife was driving and said there was a big puddle of coolant beneath car. the water pump spins and doesnt make noise , looks like theres supposd to be some sort of cap right behind the pulley on the pump; its not there. when engine runs theres no pressure on the top hose going back to radiator. i have changed tstat and refilled the block there but it still doesnt seem to be applying pressure to top hose. any ideas?

 

Do you see any wet spots on the engine? How much coolant?

 

A picture of your pump and the "cap" you are referring to might help. The only thing I can think of is the water bypass from the tstat housing to the pump. There should be a short hose from one to the other. If this isn't what you are talking about, please specify. As to why there is no pressure on the return hose, it may be that when you replaced the thermostat you put it in backwards, or it is faulty, or the engine didn't warm up enough. Just some guesses on that.

 

replacing the thermostat did the trick ,so odd.