Had the exact problem on my Gen 3 Coupe / Gen 3 Coyote build. Talked about it in my build thread. In case you didn't know already, those are Gates 28504 Heater Hose Connectors. Available from Amazon or Rock Auto. Two sources that I've used. Make sure they're the actual Gates branded products. The ones that came in my kit from FF were compatible but not branded Gates parts. Comparing side-to-side, the Gates appears to be a higher quality part. I replaced both on my build. The leaking one and the one that hadn't started leaking yet.