My 01 Dodge Stratus is having overheating problems. We have replaced the radiator, thermostat, and the water pump. We ran the car for 15 minutes with no problem but when we gave it gas and idled it at 1500 rpm for 2 minutes it started spewing water out of the overflow. The fans are kicking in. The water is a rusty brown color however there doesn't seem to have any water in the oil. I am at my wits end as to how to fix this.