The difference between Html.Action and Html.RenderAction

Try:

@{Html.RenderAction("Breadcrumb", "Navigation", new {SeoUrl = Model.CarlineBucket.SEOURLName});}

@Html.RenderAction() generates a write call to output something on the page and in your case you are not doing so because RenderAction renders the result directly to the Response.

Instead of

@Html.RenderAction()

Use

@{Html.RenderAction();}