If you dead head the oil, you can blow the pump apart because there's nothing to stop it from building pressure. You would know that real easy and it can happen in a matter of seconds. There'd be oil all over. My Cat with quick attach hoe has warning labels on both the hoe and the machine. If the oil goes through the loader valve first, then most likely the relief valve would save catastrophic failure if it was noticed quickly and the machine shut off. That being said, relief valves can sometimes stick. I wouldn't let my brother borrow a screw driver if he did something like that to your tractor. Then I'd give him a shot upside the head and if there was a lot of damage, congratulate him on his new tractor purchase. Amazingly the same price as your new tractor. Some people just shouldn't run equipment. I'd tell your brother to leave it parked and you'll check it over before you take it home.
I know someone(never had a tractor) who bought a new Kubota and complained the shuttle would grind. I told him to talk to the dealer but first read the manual and see what it says. I saw him about a month later and asked if it still grinds. No, he just pushes the clutch every time he changes direction. I asked if he read the manual, no! Talk to the dealer, no. I don't know how a Kubota shuttle works but you can't fix stupid. For sure the manual and the dealer would know the proper way to use it. My best hypothesis is he didn't want to feel stupid asking, figuring what can be so complicated about driving a tractor. This about a 50 HP tractor with a loader and I think a cab so it's a pretty serious chunk of money to guess how it works. He talked to the dealer about it being light in the back when picking up round bales because the dealer told him it would lift them but not a word about the shuttle. Sometimes you just have to shake your head and think WOW, how can people be so dumb. This isn't a toy and you can get seriously injured or killed if you don't what you're doing.
