Noises coming from T-stat housing-WTF!!!!!

Guys-

just like the title states, After the heads/Cam and flushing the coolant from the motor, have been hvaing major noises from the T-stat housing, like metallic click clacks and some type of popping...Like somehting is rattling aorund in there...yet the fan still works.
My set up consists of a MKVIII fan with a thermal sensor inside the FMS T-stat houing 3/8 NPT sensor. The Mr. Gasket 180 T-stat when put back mustve been hitting it, So we took it out and replaced it with a stant 180 and it still makes this dayuuuuuuuuuuuuuuuuum noise? Whatta ya guys think about this? Anyone ever had this same problem? Could it be the PAINLESS Thermal sensor switch went bad and makes noises when going on and off maybe from making contact before? Yet the E-Fan works stilll-i dont get it!

Needdddddddddddddddddddddddddd Help please-any input!
Anthony

I was gonna do that, But when i took the T-stat housing off and switched my sensors around without having any interference with the automtere gauge senor in the T-stat housing, at all now, once i put everything back together tonight, i will see... I ordered a new T-stat, a new thermal sensro switch as well as switching the sensors without having any interfernec at all that i can see visually-because nothing can hit or interfere with the T-stat at all-Its too high in the housing.
Anthony