Is it the water pump ?

I have a 1997 300 tdi, And today i heard a funny noise and when i opened the bonnet the fan belt had slipped off one of the pulleys which is at the top just above the alternator, I was only a couple of mins from home so drove it back and had a better look and by this time the belt had come completely off and this pulley which is at the top was all loose and wobbling about but im not sure what this part is ?
Im thinking its the water pump but am not totally sure so could someone let me know as i cant find any diagrams anywhere on the net.
Cheers guy's......

sounds like the water pump to me, the bering has collapsed and you need a new water pump

Cheers yella, dont spose you know how easy it is to do, do i need to remove the other pulleys to take the pump off, because it looks like to me that the bolts may not come out because the others are in the way, if anyone knows HELP me please! lol

Hi kenny b, try this.
remove hoses and slacken water pump and power steering pump pulley retaining bolts. remove the drive belt.
remove centre nut from drive belt tensioner and manoeuvre pulley upwards and withdraw tensioner from retaining stud.
remove pullyes to water pump and power steering pump.
remove 8 bolts securing water pump. MAKE A NOTE WHERE THEY CAME FROM AS 3 OF THESE BOLTS ARE THROUGH BOLTS.
if its a bit hard to take off, give it a gentle tap with a BLOODY GREAT HAMMER eeeerrrr no, sorry, piece of wood.

make sure when putting on the new one the mating faces are clean and youll need a new gasket. bung back together, top up and bleed the cooling system jobs a good'en.

torque settings for the bolts im not sure on but at a guess no more than
20 lbf ft.

Cheers muddee, Il give it a go one day this week as it dont sound too bad a job to do.