I have a 2000 mitsubishi it looks like its leaking antifreeze

There could be many causes for a small leak, including foreign debris, small crack or loose hose. Using just water with no antifreeze can damage your radiator in sub 32 temps so always mix with coolant/antifreeze. One temp solution is buying stop leak from a auto part store, another remedy I've heard work is putting black pepper (finely ground) in your system to stop small leaks and it actually works. Good luck.

Check the water pump.. Check the pullys

Very likely a bad head gasket. Be sure to get it checked and fixed. If your engine over heats or if the gasket is also leaking into the cylinders then you could cause serious damage to your engine.
More info

That would be a leaking heater core.It will need to be replaced.

No , but whoever did your A/C probably put a Dye in the system to detect any leaks, an it is green, which is the same color as most coolant/antifreeze.. But if your coolant level is not getting low, i wouldn't worry about it, because it is probably the Dye. Now if your coolant level is getting low, you may want to have the system pressure checked.. Good Luck.. Also it may be your Heater Core.. On some vehicles, the heater core, an the evaporator( where a/c leaks), or sometimes in the same casing unit. But again, you will need to have your coolant system pressure checked..

if its colored and smell its antifreeze so its the heater core, if its clear like water then its just condensation from the evaporator and that is normal

Use a 50/50 mix of antifreeze and water. You can go to any auto parts place and purchase the pre-mixed 50/50 blend to put in the van. The next time you look in the coolant recovery jug on the van, you will see the color of antifreeze. (Do not purchase a pink antifreeze and mix it in with a green antifreeze) Stay with the same color you have in the van. Hope this will help you.

It probably wasn't the thermostat in the first place. Sounds more like a head gasket. Check the oil to see if there is antifreeze in it (green color or sweet smell or high oil level) this could cause problems, but brakes locking up? That wouldn't be caused by antifreeze.

If the air coming from your heater smells like antifreeze or your passenger side floor is wet with antifreeze, then your heater core is shot.
Till then it's fine as it could be a $700-1000 job.
Report those Bozo's

If you are smelling antifreeze then there is going to be a leak.
Look at the drain hole for the A/C drain pan. You may not be seeing it because it is mixing with the condensation from the evaporator. Sounds like a heater core or hose connection at the heater core.
Good Luck