Okay, so for the past few months, my car has had a problem with overheating 
Sofar what I've done was flush the coolant and ran a cleaner through the cooling system then replaced it with some new coolant. The problem is that when I idle for a little while, the coolant starts steaming out of the overflow reservoir and if I pop the hood it sounds like the coolant inside the reservoir is boiling as steam comes out of the cap. Usually, when steam starts coming out of the reservoir, my temp gauge shows normal operating temp 
so i'm not sure what that means .. But today it was different. While I was driving today, I saw the temp gauge start creeping up so I turned on my heater as I usually do, but this time it didn't help. The temp gauge just kept creeping up, so I decided to pull over. When I pulled over, the coolant reservoir was not bubbling or anything, and it didn't feel hot at all. So I got back in the car and started it, and the temp gauge read normal again. I drove for maybe a half of a mile and it started creeping up again, so I turned on the heater again. I noticed that the heater didn't feel hot, instead it was just warm. Then all of a sudden, it blasted hot air, and the temp gauge started to go down. After about a minute more of driving, it started heating up again, but I was luckily near my work so I could just pull into the parking lot and freak out without having my car on.
So now, what would cause it to act this way ? I think I'm out of coolant, but I'm not sure as there's nothing in the reservoir. Also, why would the coolant boil and steam out of the reservoir ?
Sofar what I've done was flush the coolant and ran a cleaner through the cooling system then replaced it with some new coolant. The problem is that when I idle for a little while, the coolant starts steaming out of the overflow reservoir and if I pop the hood it sounds like the coolant inside the reservoir is boiling as steam comes out of the cap. Usually, when steam starts coming out of the reservoir, my temp gauge shows normal operating temp so i'm not sure what that means .. But today it was different. While I was driving today, I saw the temp gauge start creeping up so I turned on my heater as I usually do, but this time it didn't help. The temp gauge just kept creeping up, so I decided to pull over. When I pulled over, the coolant reservoir was not bubbling or anything, and it didn't feel hot at all. So I got back in the car and started it, and the temp gauge read normal again. I drove for maybe a half of a mile and it started creeping up again, so I turned on the heater again. I noticed that the heater didn't feel hot, instead it was just warm. Then all of a sudden, it blasted hot air, and the temp gauge started to go down. After about a minute more of driving, it started heating up again, but I was luckily near my work so I could just pull into the parking lot and freak out without having my car on.So now, what would cause it to act this way ? I think I'm out of coolant, but I'm not sure as there's nothing in the reservoir. Also, why would the coolant boil and steam out of the reservoir ?
How would I find out ? Also, how would I find out for sure that the radiator cap is busted ?
