1999 Dodge Neon Radiator Cracking

Since I changed the water pump in my car, it started having this problem. The car would run without problems, but when you parked the car, the coolant deposit started boiling fluid. Tempeture gauge never indicated overheat, but when turned on right after the boiling, the temperature would be to the red, but if I started the engine, it would go back to normal. A few months after that the top of the radiator turn yellow, it used to be black, and cracks started showing up. I was able to fix 2 of them, but another one just showed up, again. I am afraid that if I replace the radiator something in the engine is going to damage the new one. Your advice is greatly appreciated.