My 2001 Jetta 1.8T is throwing a PO442 code (evap system small leak). I've done a bunch of searches and figured out what this means; I just can't figure out how to fix it (A new gas cap didn't help, and the N80 purge valve seems to hold pressure if I try to blow through it). And I have cleared the code many, many times and it always comes back.
I'd like to see what others think of my methodology: I read the write-up here on how to do a home leak test, which gave me the idea of simply blowing smoke into the line and seeing where it comes out. So I disconnected the evap line inside the engine compartment and blew smoke into it. It looks like smoke comes out at the intake air filter (cylinder-shaped part on the bottom) on the leak-detection pump back in the right rear wheel well.
I'm thinking that I shouldn't be able to blow air through the pump like that; that it ought to hold pressure. So does this sound like a likely cause of the leak? Would it make sense to replace the pump? I don't want to keep replacing expensive parts if it's not going to fix the problem, but I'm not wild about paying the $950 my mechanic wanted to work on it either. Any thoughts?