2004 Impala coolant problems

Need to figure out this coolant problem....

I have a 2004 Impala that recently has been overheating. I found a rust-colored film inside the radiator and cap, though the radiator was full. I bought this car used from a dealer and they had been using standard coolant, NOT DexCool. Should I just flush and switch to DexCool? I also found a leak in the radiator, though I'm not sure if that's caused by the wrong coolant.....any help?

Need to figure out this coolant problem....

I have a 2004 Impala that recently has been overheating. I found a rust-colored film inside the radiator and cap, though the radiator was full. I bought this car used from a dealer and they had been using standard coolant, NOT DexCool. Should I just flush and switch to DexCool? I also found a leak in the radiator, though I'm not sure if that's caused by the wrong coolant.....any help?

I flushed my 2002 base model (bought new) about a year ago, replacing Dexcool with standard "mixes with anything" green stuff. No problems yet. I also had the brownish sludge buildup on the rad cap (level OK), but the oil looked ok. The plastic tank was pretty oily-looking, too, so I used brake cleaner and water to clean that out. Looks showroom clean now. Never any overheating problems with my car, although it seemed to be creeping a bit higher on the temp guage than it originally had. Since the flush, it always runs cooler, but no performance issues. Things SEEM to be OK, but I'm watching it closely (intake gasket problem suspected). Regarding your car, you say it's overheating, but do you mean creeping up over 200 degrees before the fans knock it back down? That's what my Impala was doing. I'd try the simple stuff first - flushing and re-filling with fresh coolant. If that doesn't help, try a new T-Stat.

I'm told by the dealer this is normal, it protects everything from rusting. I complained anyway and they flushed it free. That was a year ago. It looks that again.