We have 2008 Express in our fleet that keeps breaking one of the lines going to the hydraboost. It has blown this line at least 4 times now in the last 3 years. This most recent time I had a local company make me a line and it lasted longer then the OE replacements. Any ideas on why this might be happening? 3 different mechanics have worked on this issue.

 

maybe the pressure regulator has failed. There should be a pressure test port somewhere.