BMW

About 3 days ago i notice my car was semi overheating.. (going past middle mark) and i stopped at a place and got some coolant and put new coolant and water in there.. ever since then my car is running okay but its when i idle that it likes to get hot again.. when im actually driving it stays cool.. anyone know what it could be?? i hope its not a major radiator problem or anything because i dont want to put money into the car.. (i plan on buying a new one soon) but for now its crucial that i keep thsi car running.. so any ideas?? please! ! its not the fan i dont think because the fan turns on when the cars on.. | thanks!

Check the thermostat in the engine and all the hoses for leaks. most likely the thermostat is sticking partially closed. you can test it in a pot of boiling water. drop it in and see how long it takes to open. it should open quickly in boiling water. if it stays closed, change it. easy and cheap to do yourself. good luck.