Hey there I've gone through 3 frost plugs/block heaters in about 2 months and it looks like I'm about to go through my 4th very soon here. I bought the truck with 172000 kilometers and got the thermostat housing replaced with an aluminum one at about 178000 kilometers and since then I've had 3 block heaters go out on me. I've had them replaced by independent mechanics first 2 times and the last time had it done at a ford dealership. I'm really at a loss for what to do here as I love the truck and other than this it is mechanically sound and has low kilometers. I've attached a photo of the leaking plug as well. Any help on what could be causing this or what to do would be appreciated thank you.

 

That is odd
Check the radiator cap, should be 14-16psi model, could be holding too high a pressure