Q: Coolant problem

It sounds like there was a coolant leak but coolant leaks can be either a cause of overheating or a consequence of overheating. In your circumstance, you hear noise. Check the level of engine oil. If there is not enough oil, that can cause both noise and overheating. If the coolant has leaked out, of course don’t run the engine. If you want to get the car running what I suggest is request a leak diagnostic and repair. In the course of, the mechanic will probably try re-filling the cooling system first (assuming any leak that exists is small enough that not all the coolant immediately flows out) and then briefly run the engine (after making sure there is adequate oil) to determine the likely source of the knock. The reason for that strategy is to determine the extent, if any, of the damage. If there is engine damage, it will be pointless to fix the cooling system because obviously the engine will have to be repaired first. All in all, best to just request a leak diagnostic and the mechanic will evaluate the entirety of your situation and guide you from there with the least cost repair strategy. If you have further questions or concerns, do not hesitate to re-contact YourMechanic because we want you to make the most of your repair dollars and help you to get the best possible results.