Once I get the car up to around 200-205 degrees the coolant starts to bubble and overflow out of the coolant reservoir. What's wrong?

 

Have you tried replacing the radiator cap to see if that fixes it...?

 

^ what Joe said.

 

Brand new radiator and cap. Thinking my problem may be that the coolant hose coming out of throttle body is going into the overflow tank rather than feeding back into the radiator. Sound right?

 

check hoses, thermostat, water pump, and if does are not it, then either a blown head gasket or crack head. Good luck.

 

Well shouldn't the hose at the cap be the return line to the coolant reservoir? Or is it correct that the hose from the tb is going to it?

 

lower port on radiator neck (below rad cap interface): steam vent crossover/TB.

upper port on radiator neck (right on rad cap interface): overflow reservoir.

 

My radiator doesn't have 2 ports. Just has the one directly on radiator cap area.

 

Can I just cap this off?

 

No...

the steam crossover tube has to vent to some low pressure side of the cooling system...

otherwise you will see overheating.

 

What radiator do you have...?

 

It's a Be Cool radiator

 

Be Cool radiator has the right ports on the radiator top one goes to overflow the bottom one goes to steam tubes

 

Mine doesn't. There is no bottom one

 

So without having the port on the radiator for the steam tube where should I connect it? I was told to get a t-barb and run it off the overflow port and connect the overflow tank and steam tube to it. I believe this would leave me with the same problem though..right?

 

well it either has a plug in it, or you have the wrong radiator. i know because i have a becool radiator. the port right below it had a brass barb fitting to run your rubber hose to for the steam ports

 

The radiator isn't a vehicle specific radiator. My ls is in a g35 so I went with a dual pass circle track radiator (this was suggested by someone with a 350z who did the same swap).
So any suggestions as to what to do with it from here?

 

Find some place to tap/install a fitting on the low pressure side of the cooling system.

 

Can this be in a coolant line or do you recommend on the radiator?

 

Either the low pressure side of the pump (see that flat circular place next to the outlet port) or just below the rad cap interface of the radiator.