[Vwdiesel] Replacing the fuel filter/ bubbles in fuel lines

[Scott Kair]

>>Under the tank on the passenger side is what looks like a box with a
round thingy that can be turned. It looks like the fuel lines run in
this. What is under there?<<

    Serious headaches if you break it.  It's a water separator for the fuel
system, ingeniously placed where road gunk, salt and water can work their
magic.  Check in your trunk around the spare tire- you may get lucky and
find the original kit for it, which resembles an oversize colostomy bag and
tube.
    The usual failure mode seems to occur after attempting to drain it and
consists of fuel leaking from it when the drain tap won't close afterwards.
    Seriously, it seems to be a redundancy, since fuel filters perform the
same function.  Due to the possibility of not getting it shut after draining
it, I'd consider looking at it only if no other cause becomes apparent.

    >>Where is the most likely spot for the leak to be? I can see most of
the
line except where it goes through the sub frame under the passenger
seat.<<

    I should have mentioned this in the earlier post.  For some reason, with
the newer filter, I really had to crank the clamps on the filter lines down
tight.  If the only changes you made to the system were the fuel filter, I'd
look at them first.
    BTW, did you fill the new filter with fuel or additive and moisten the O
ring/ seal?
    Keep an eye on the top of the filter if none of that works.  The
thermoswitch is fairly delicate, and transplanting an older one onto a new
filter can crack it.   The one that came with my car leaked just a little
bit of fuel on top of the new filter, which was detectable only when dirt
repeatedly stuck to it. A crack elsewhere on it might let air enter the
system.
    It's also possible for the lines from the tank up to the filter to rot
or corrode, but if you weren't getting air before, look to what was changed
in the system.
    HTH,
    Scott Kair