Thanks for your inputs guys . Anyway, napalitan na ng copper and so far ok naman. Actually I prefer na palitan ng bago sana kaya lang wala pa pera ngayon. Kapag naka-ipon na.

Something interesting I found out by google-ing. May shop sa US na nag-rerepair ng radiator na ang ipinapalit sa plastic inlet tank ay plastic din unlike here na copper. I just wonder kung meron din dito sa Pinas na gumagawa nyan. Cause if CivicVTI is right, then replacing with plastic is the right thing to do. But Dest has point as well because the function of the pressure cap is to release excess pressure. *Dest, yung tank ba ng radiator ng car mo copper din?

So the question actually is, which is better? copper or plastic? Everybody who have experienced this problem is welcome to answer this question.