UK Car Repair: 75 Triumph Spitfire fan noise, noise question, rotation movement

Question
QUESTION: Hi There,

I drive a 1975 Triumph spitfire.  I recently encountered a new problem.  Its cold out now, i'll say that, but it might not affect anything.  Car drives fine.  BUT, when the revs are up (either by pushing the gas in, or by choking) it makes a terrible grinding noise.  I popped the hood, and stuck my ear in.  Its definitely coming from the cooling fan.  but it doesnt make the sound while idling.  I checked all the usual stuff, doesn't appear anything is caught in the belt, and the fan isnt rubbing anything.  Car has oil.
its the exact same sound that it used to make in the hot summer while choking when it was hot out, only then, it was super periodic, like one small grinding sound that would last half a second, every five seconds.  Now its constant, and louder. and does it when I apply the gas even slightly.

thanks, Dan

ANSWER: bearings in the fan are worn.. with engine off see if (that) there is play in the fan bearings? = replace the fan or just the bearing, whatever part is easiest to find.

---------- FOLLOW-UP ----------

QUESTION: how would I know there is "play" i can turn the fan freely with my hand.  and I can "wiggle" it perpendicularly to its rotation about 1mm, just barely really.

i looked on ebay, fan BLADES are available but no mention of bearings.  Would they go by a different name? Its not the viscous clutch/coupling is it?

Answer
Viscous coupling yes..
more than a few thou of wear in the bearings of this coupling and the fan can vibrate -

the coupling consists of an input, a clutch and an output, 3 separate bearings in there - a little play in one, a little play in the other.. the perpendicular-to-rotation movement becomes magnified, the fan is OOB and rattles around making a roaring grinding noise.