accessories making noise 1998 gmc 5.7

I am back like a bad penny. I had a squeeky belt so I changed the belt,idle pully and the tension pully and I still had noise. today I also heard a poping sound like rocks hitting the wheel wells only it was comming from the engine/more from the front of the radiator. I decided to take it to a garage that could listen also. about six miles away the noise quit and now i can't get a squeek out of anything. I took off the belt when The new knock started just in case it WAS the engine and all I heard was the motor. there is nothing comming from the wheep hole in the water pump. The last thing I did was change plugs. (108Ks) this knock only happens when the engine is just warming up not when it is cold and apperntly not when it is really warm.