hello to all my friends.
you have helped me through a month long battle with oring replacements caused by the new ultra low sulfer diesel fuel.
have replaced many orings, shutoff box, orings in the injection pump and the pre filter. today it was a new fuel filter and ring.
no more leaks. but a bubble still appears in the fuel line on top of the pre-filter, immediately after shut down, that is longer than an inch.
starts and runs good.
thank you again, have saved at least $2k on this repair because of you.

That's perfectly normal, mine does it too. It's just fuel draining back into the tank after shutoff.

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99 E300 TD -- sold
01 540i 6 spd

thanks for your fast reply. never noticed that before.

b100 for 3 years and no fuel related problems; untill the first freese and the switch to ULSD happened at the same time.
aparently biodiesel swells the orings, and the lower aromatics of ULSD hardens them. a bad combination. just waiting for my truck to start leaking and i'll be at it again.