04 Volvo VNL 670 heater core leak help

Hello, I am posting this for a friend who drives an 04 VNL 670 with the Cummins engine. The hose before the heater core is leaking, so as a temporary fix he cut the hose and reattached it. I'm not sure which hose is bad as he's still on the road, but I would be helping him replace both hoses when he comes back. The problem is, he said he can't see the other end of the hoses. I know this is a long shot but does any one have a DIY for the procedure or at least some kind of diagram of the cooling system? Usually the inlet hose will be coming from radiator and the outlet going to the block on most cars, but I've never worked on a Semi before, so I need all the info I can get. Thank you for your time.