1998 VNL Question ?

I'm looking into buying an older tractor, it's a 1998 Volvo VNL, D12 with 10Spd 877k, i never owned a volvo and need info before buying this thing, what should i look out for, are these trucks known for a specific problems ? any info would be great thanx

 

the one i'm looking at has a ved12 @425, has been sitting over a year in a yard, was a backup.

 

hey pablo i got this truck a few days ago and drove it home, it was 150 mile everything looks to be ok i guess, good oil pressure and engine temp, but i do feel like the truck runs kind of harsh, it doesn't really sound like a misfire but maybe its just how this motor runs ? when i stood next to the intake opening on the pass side it makes a strange sound almost like an old air compressor running, it's kind of hard to describe. what do you think of these motors ??? (the dash shows "engine timing sensor" message, could this be the problem ?)