Has anyone seen a radiator fail like this?

• Just replaced my leaky radiator on my 4.0L with a mopar factory replacement


• While i had it out I did some preventative maintenance and added a new water pump (it looked like it still had the original), pulley, tensioner etc


• Ran cooler than it has ever run for a few days then all of the sudden it overheats... i pull over to let cool and check it and I see evidence of coolant spray under hood.


• I initially assumed it was the cap releasing pressure but just found this completely missing plug/endcap of some sort (can't find it anywhere, probably on street) Has anyone seen a brand new radiator fail like this? I don't see threads, it is a smooth surface like a plug was 'pressed in' at the factory...the opening is on the engine side of the radiator.
  


• also- i just pressure checked the radiator cap and it is releasing at ~18psi (it was a new cap that came on the radiator) -- thanks for any feedback anyone can offer--unless there is a common or reliable fix (i can't find a part/part# for this plug/cap if it exists) it looks like i'm pulling this thing back out. I'm open to suggestions however *sigh

Attached Images

end_cap.JPG (18.1 KB)