Its a lot more complex as it seems. At least 3 different pumps designs + different timing chains during the years...
A bit of summary of what I have found so far. Hope it is helpful.
1. The very first water pumps appear to be the seriously flawed ones - 1 seal / 1 gear/teeth design
Leaks from seal or from gear shaft.
2. Somewhere in the 2011-2012 there is the 2 seal design / 1 ?? gear/teeth water pump
Not supposed to leak from seal since there is a hole after the first seal for leaking out.
Still the gear shaft is problematic so it appears to be leaking from there directly in the engine.
Plus the gear shaft appears to be stressed by the timing chain.
3. Later they add a redesigned (2013 ??) - 2 seal / 2 gear/teeth water pump and as we see in the posting.
5.
2015 Explorer has water pump part no. DG1Z-8501-C
Replaces: AT4Z-8501-A, DG1Z-8501-A, DG1Z-8501-B, PW-515-, PW-533-, PW-566-, AA5Z*8501*C, PW*518*
6.Sometime 2016 may be... the very latest one -
Explorer 2017+ - water pump part number AT4Z-8501-B
which replaces AT4Z*8501*CA, PW*531*
From what it seems Ford is at least trying. Every few years they try optimize the pump to mitigate the issue , given the fact the design (internal water pump) cannot be changed.
It appears on the latest Explorer 2016+ things are much better from that perspective.
got me wondering ...do we have somebody with leaking water pump (less than 120K miles) on the latest models 2015+...because from what I could see anywhere in the forums and on the Internet, seems only the first generations Explorers/Edges, etc are complaining so far. Don't see anything from 2016+ where the very latest design is incorporated.
Kind of reminds me of back in the days when we had to change the timing belt and we always changed the water pump at around 100K. Except here its a lot more expensive for labour