Employee obsessed with a buying new company van?

Hey, so we are a family business and there's a nefarious employee that needs dealing with.

I’m concerned as one of our employees (he's a thief and greedy for money) has been trying to convince my dad to buy him a new van. Even

two years ago he damaged the front of it and i'm sure he crashed into a wall hoping try and get a new vehicle. A week later one of the other employees told me hes desperate for a new van.

Now you have to wonder why he wants a new van so badly?

He must be taking it to his own mechanic, and swapping the clutch over etc and selling parts.

With the vehicle he had before, it was ridicious we had to change 2 clutch within 3 years, coolant always leaking, tyres always being swapped, transmission issues, new gear box and loads of other issues over the years.

He takes the van home with him.

I'm sure he doesn't just destroy the vans because hes a sadist… Sometimes its as if hes doing black magic :L

So we have ordered a new van, surely he cannot change clutches or ANYTHING as its under warranty, and they will examine if there is any problems. Our company mechanic recommended stamping everything under the bonnet and everywhere.

I need to find some hard evidence, and as this new van will be in my possession for the next 2 weeks which gives me time to prepare and gain evidence to show my father how stabbed him in the back all these years.

Could anyone advise what he's trying to achieve or anyway I can prevent him getting away with what seems like stealing vechicle parts on the new one please.

Any advice would be much appreciated.