What is this part and what does it do?

[SMIT]

What is this part and what does it do?
The part does not spin freely like it should and needs to be replaced. Any ideas?

[SweetWagon]

Thats the Waterpump, it will need replacement, not too bad of a job, there is a how-to thread on it. looks like your belt tensioner is shagged also.

[VTS5]

What is this part and what does it do?
The part does not spin freely like it should and needs to be replaced. Any ideas?

Thats water pump pulley.Sounds like the bearing is stuffed.

[SMIT]

thanks allot people. Much appreciated.

[AttaBoy]

Don't forget to bleed the system once you replaced that.

[ryand]

whats happened to your idler pulley on the tensioner...looks like somethings hanging off?

[Harvs82]

What is this part and what does it do?
The part does not spin freely like it should and needs to be replaced. Any ideas?

As others have suggested, its the water pump. I was just looking at your photo there... a couple of alarming things to note, firstly being that it looks like the tensioner pulley is totally buggered... but also, have a look at the idler pully between the aircon compressor and the harmonic balancer... From the looks of the photo, you can see that the belt has only been sitting on about half the pulley.. and that the pulley itself looks like it is sitting on an angle... might want to check that out ASAP!