What is high pressure overflow on radiator

there is a 1" or so plastic elbow at the end of an about 1/2" hose that comes from the overflow tank and goes into the top of the plastic part of the
radiator. this appears to be called a high pressure relieve. There appear to be two clips (from radiator) that hold on to this elbow. Can this part be repaired? seems a difficult item to remove/check. I assume there is a o-ring inside .... sure hope it's not my rad.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.