Noisy Engine?

I have a 1991 Explorer XLT w/183,000 miles on it. My problem is when I start
her up.She makes a high pitched squeal that is sort of rythmic. I can tell
it is from the belt or the bearings. It stops after the engine is good and
warm. I wonder if I should replace the belt, but upon inspection it looks to
be in order. I replaced the water pump about 2.5 months ago, along with the
upper radiator hose. The hose has a slow leak between the Therm cover and
the hose that I am trying to sort out. Could the liquid from the hose be
causing this sound and how worried should I be. She runs as smooth as a
14-15 year old truck should, little to no oil loss and noCEL's.

Thanks in advance.