Water Leak

2011 Cruze Eco and I just had to add to the overflow. Took almost a half gallon. A little concerning since the car is only 1.5 years old. I looked and could not find any visible leaks but am not able to get the car in the air since we are 500 miles from home. I need to change the oil next week and I'll look under it then. If memory serves the water pump is only covered for the first 36000 miles? Ours has 61000 on it right now. If it's the water pump are there any how to bulletins? I will do it myself before paying a dealer.

Thanks in advance.....