Found a crack on top of plastic reserve coolant tank.

[Waterloo]

One thing I learned on these coolant bottles, the dealer prices are all over the map. I needed to replace mine and was quoted $200 to $745 from the dealers... I bought the $200 one from a dealer and had it shipped. I had no clue Dorman made these at that time, so shop around if you are going with an OEM bottle, check eBay too.