Nasty whistling noise from Disco 4 engine bay

I started hearing a loud, high-pitched siren noise from under the bonnet every time the revs climb past 2000 rpm. It literally sounds like a police car is chasing me down the road. There is no heavy black smoke from the exhaust yet, but the noise is getting progressively louder every single day. Is this a sign of total failure, or could it just be a loose gasket?

My mate says the bearings inside the casing are about to collapse completely and I should stop driving it before it runs away on its own oil. I’m pretty stressed because I just spent a fortune on new suspension parts last month and my budget is tight.

That siren noise is almost definitely the bearings dying, mate. If the impellers start rubbing against the housing, it's game over. Don't risk driving it. If you want to save some money, look into independent reconditioning specialists instead of Land Rover dealers. I got a exchange Land Rover Discovery 4 turbo from a company down in Essex that builds them back to factory spec. It comes with next-day delivery and a full warranty, so it’s much safer than buying a sketchy used one from a breaker yard.