i recently had a 2001 1.5L accent and never had this problem but ive been riding in my dads 1.6L 2002 accent which has a constant hissing sound while the engine is running. sounds like a rotary hiss. im not sure what it is and were hoping its not something drastic but he doesn't want to think about it b/c he doesn't have the money to replace anything right now so he put it in the back of his mind but i don't want to see it to lead to bigger problems. he was thinking water pump but i know nothing about water pumps so im not sure what to think. next time i get a chance ill check under his hood to locate the sound, but if anyone could help that would be great.