Idling issue

Vehicle has been fine until this morning. We did have to replace the radiator a few months ago but doing nothing out of the ordinary this morning it stalled at a stop. So I turned it off and started it again and was fine at a stop. Under 2000 rpm it's fine. But if I go over 2k and stop it will stall and shut the engine off. If I go 15k its fine. I don't know what the issue is. I'm going to have my shop look at it but they think its a hose of some kind just hearing about it. It passed inspection recently and has its fluids topped off recently. no visible leaks but it's been wet lately and our communal garage has a lot of liquid on the ground, but the liquid that appears while parked at the garage does not appear parked at work, so I don't think it's leaking.