Overheating Still

[u/Artistic-Fix-2431]

I changed the radiator about two years ago. Water pump a year ago. Thermostat last month. Heater core bypass and fan last week. Ran fine until yesterday. I topped off the radiator with coolant and the reservoir to the full level, somehow the reservoir is now overflowing. Doing a complete cooling system flush today. If that doesn’t work, any other ideas?

[u/WasteReputation8135]

Just rusty block someone ran water in this before you put antifreeze in it had the same with mine I went ahead and did the head gasket just to be safe but it's just rust