I think most will agree the pulleys on these units get pretty noisy over time - I know my wagon certainly was.
Today I pulled the tensioner off my wagon, and unbolted the two pulleys.
You can use a couple of small flatblade instrument screwdrivers to pry the bearing seals off - be careful, they'll come off without puncturing.

You'll most likely find the original grease to be crappy and crystalline(if there's any left), so you can wash it out with petrol/metho, etc and a brush. The bearings were only noisy due to dry or no lube. I found the ball races to be quite okay with no great sideplay/looseness, so I repacked the bearings with High Temp bearing grease and pressed the seals back in. Put the tensioner back together - make sure you put the smooth pulley back in the correct orientation (mainly for wear purposes - if you look at this pulley you'll know what I mean).
Installed the tensioner and installed the drivebelt . . . . . . boy, what a difference, bugger all noise - only normal engine noise.

It was certainly an hour well spent - if your bearings need replacing, they are NTN 6203LH.
I would only attempt bearing removal with a press, and be careful as the plastic wheels might split.
Of course you could buy a new tensioner, but I don't think they're cheap . . . . .

...good advice - but if you don't have a press or access to one - another good solution is to purchase metal (afterarket) pulleys - they'll outlast the crappy Ford plastic ones many times over

They pulleys off of the early e series arent adaptable are they? They're metal ones!

What noise does it make when its on its way out?