car overheating

First, do not take the radiator cap off when the car has been run or is even hot to the touch unless you want to risk getting scalding coolant on you. Very dangerous. Water boils at 212F and your car should typically run at 180-190F. The mixture of coolant and water you put in the cooling system will increase the boiling point of it to about 220-230F and the radiator cap will release at about 15 LBS pressure to expel hot coolant into the overflow tank. It will be recovered later when your engine cools down. So, no, the coolant should NOT be boiling when the cap is removed. Since you have changed almost everything in the system except the upper radiator hose, I would suspect that you have some trapped air in the system that is blocking the flow. Try removing the radiator cap with the engine cold and running the engine to purge any trapped air. The radiator may "burp" coolant out of the throat during this process but that is just the trapped air working its way out. When the system seems to be flowing freely, shut down the car, let it cool and add coolant/water mix to the rim of the cap. Install the cap and fill the recovery reservoir to the "Full Cold" line and you should be good to go. Final note, if you were not filling the system with a 50/50 mix of coolant and water, drain it before doing anything else and refill with the right mixture. Then proceed with this process. Good luck.

There's a plug on the thermostat housing. When engine is cold, fill radiator with coolant, close it back up, loosen the plug or remove it completelly, run engine for a while til it reaches normal temperature. You'll see some coolant bubble out of the plug hole, install plug back in place and shut engine off, should remove air out of the system. If u still have the same issue, check the cooling fans to make sure they're working