So this is an EA211 family engine? - of course it is if the water pump is on the other end of the head to the timing belt. It's driven off the back end of one of the cams (exhaust?) by a small toothed belt and has nothing to do with the main timing belt which is on the other end of the engine on the drivers side of the car. The pump has a black plastic cover which protects the belt which drives it. You can see it in the first picture in this article at the top of the engine:
https://uk.motor1.com/news/430137/3m-milestone-ea211-vw-engine/
When a timing belt is being done this cover has to be removed so that the locking tools which immobilize the cams can be installed but neither the pump or the little belt which drives it need to be dismantled, just that cover to be removed. All the "action" takes place at the other end of the engine. So you can see there is no need to disturb or replace the pump if it's running all right.
Here's an example of the pump and it's little drive belt (not the right one for our actual engine, but it gives you the idea):
https://www.ebay.co.uk/itm/New-OEM-...696562?hash=item1a9ab4e6f2:g:R2UAAOSw~tpfv7Bt
It's a modular set up and includes the two thermostats - yes, just to add to the complication, as if there wasn't enough already - our engines have two thermostats!
I've been giving a lot of thought to this pump as my timing belt is going to be renewed this coming spring. My immediate "gut" feeling was to get it done but I think that's because I've become so used to having engines where the water pump is part of the timing belt drive train - So if the pump bearings fail the belt is very likely to either jump teeth or come off altogether which is often terminal for the engine as the pistons and valves will become indecently intimate! However with the pump not being involved with the timing belt setup at all - to renew it the only shared operation would be removing that little black cover - I've decided to leave it alone with the one caveat that they carefully check the condition and tension on the wee "mini" belt when they've got the cover off. My only slight worry is that there have been a small number of reports of water leaks due to warping of the plastic body allowing leaks round the seals. I really have to ask why oh why make a component like this which is going to be subject to repeated heat cycles (and maybe excessive heat if something goes a wee bit wrong) out of PLASTIC? They (all the manufacturers) have been making engine parts out of plastic for years and warping remains a big
problem. But I suppose it's saving them at least half a crown on every engine so they'll carry on - as long as it gets out of warranty before it becomes troublesome eh? I tend to have a regular weekly regime of under bonnet checking, inherited from years of running bangers when I was younger and my interest in older vehicles to this day. So I think, as long as I carefully keep an eye on coolant level, I'll catch it if a leak starts, before any harm is done.
PS At least we can rejoice in the fact that they didn't saddle us with a dual mass flywheel (or that is to say my 1.0 litre 3 cylinder 95hp CHZB doesn't have one.) Anyone know if any of the petrol variants do? - And those of us with the 3 cylinder engines don't have balance shafts either! just that "clever" intentionally out of balance flywheel.