2010 Hyundai Elantra Q&A

2010 Hyundai Elantra Question: my coolant light came on,

about a month ago, my coolant light came on and the coolant was low, I replaced it and ran it for a few mins with the cap off to get any air bubbles out, it was fine, a month later my light came on again, and the coolant was low again, I had a pressure test done on it, and it started at 18 and about a half hour later it was down to 11, can you tell me what might be wrong? -
Answer 1
YOU HAVE A COOLING SYSTEM LEAK SOMEWHERE. POSS WATER PUMP. IS IT STILL UNDER FACTORY WARRANTY? -
Comment 1
not that i know of, someone said a head gasket, im hoping not, but what do you think, i put a new radiator cap on it, and there isnt any place inside the engine that appears wet, and its such a slow leak, i cant tell where its coming from on the ground -