Hello I am a solicitor with 20 years experience. I will try to answer this.
Did you buy this from a dealer?
No, it was a private sale
If you're buying second-hand goods from a private seller (someone who doesn't sell goods for all or part of their living), your rights are very weak compared with buying from a trader..
The only protection is that it's correctly described and the owner has the right to sell it (ie it belongs to him). Here, it really is a case of caveat emptor or "let the buyer beware".
So if the seller says nothing or little about the van and you buy it, then that's it. Even if it's shoddy, you weren't mis-sold, so have no comeback. Though if you were lied to you would have come back. The existence of a mechanical fault is not something you can use to claim money back from a private seller.
One thing I would say is are yo sure he is a private seller. If you bought it through an advert/ebay etc. have a look to see if the same person seems to be regularly selling vehicles then he may in fact be selling as a business and then consumer protection rights would apply.
Ok, I will check on this. Thank you