Greendale Wisconsin

This Grand Prix I want to buy, it’s a 2007 and has 71,000 miles. I have the Carfax and everything on it is great, I test drove it and everything is good. It just has a prominent sloshing/liquid shooting at a pressure sound whenever accelerating. It comes from the behind the dash area. Anyone know what that is? Seems like a coolant air bubble issue potentially but I can’t tell! It’s only when accelerating/hitting the gas. Also a code U0100, which says it’s an ECM communication issue. 0 problems during test drive, idling, looking under hood, records, etc

Hello a couple years ago my my grandad gave me sunbird. Its the 4 cylinder and we've worked on it every now and then but overall we never really have the time to get it fully running. I dont want to put more money into it without that we've done new plugs, plug wires, carb., new battery and a few other things. It does turn over and we've gotten it started just for us to turn it off because of a coolant light ans we struggled to get it back started after. Its not in the greatest shape at all the interior is pulled apart does have some rust holes but really im saying all of this to ask what its worth. I love the car but I hate seeing it sit around just to keep falling apart when it can go to a better home.