i have had the same issue and resolved it..
The problem on mine was due to the seal the temp sensor sit on top..
The coolant ran down the hoses making it very hard to find the exact leak..
Dry off all the other hoses and run it.. while watching it..
More than likley it will be this seal is its becoming pretty common, the seals are only lasting around 7 years or 110k miles..
See photos below..