Yes, it's a lousy design. (There are many others in your Volvo that you will discover!) In the grand scheme of Volvo ownership, $500 is about a minimal-cost Volvo repair. Yes, I'd fix it because the pump is there for a reason, namely to reduce emissions, and because I and most everyone else has to breathe the air. Unlike some here (typically, and amazingly, it's usually the tree-hugging 240 liberals) who think it's a badge of honor to drive an ancient Volvo that belches smoke like a 19th century steam locomotive, I think this is a bad idea. If your state requires emissions testing your car will fail testing if the "check engine" light is on.

-Punxsutawney Phil