Brown water in water jug
If its rusty you need to flush it and replace with new coolant with active anticorrosives, likely brown coolant was just water or mostly water. The commercial coolants with ethylene glycol colored green or red are mixed 50–50 with water but will help prevent rust
is the car over heating? is there white smoke out the tail pipe??
Definitely pull the oil dipstick and see if you have similar "goop" on it. If you have an automatic transmission check the transmission fluid. Same deal, look for "goop" on the dipstick. If you have an oil cooler in the radiator it could be rotted out and allowing oil into the cooling system. Same deal if you have an automatic transmission. There's a transmission fluid cooler in the radiator. If that checks out ok, you may be looking at a blown head gasket. HTH. -Jim
How many miles on her? Do u or someone else drive her hard? Has it been over heating at all?
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