So when I take off my radiator cap, it has like rusty water along the cap and around the radiator neck inside, I haven't had any problems with it though, I know my old engine had it really bad the water was even rust and junk inside, but I've had a new rebuilt engine put in AND a new radiator so what can it be?

 

well the rust is from not running enough antifreeze and too much water .My guess it is coming from the water pump . I would pop the drain plug and put a hose in to the top and turn the car on and flush it out good and do a 65 /35 % water mix and drive it for a week and see if that clears it up .

 

Boston1931, you need new fan motors AND a thermostat. Without fans your car cannot cool.

 

reaper18769, drain and replace coolant, remember more yellow GM Dexcool than water.