heavy fuel/emmission smell in cabin and tagging noise from rear (not exhaust) on 2003 Audi A4

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Any help... heavy fuel or emission smell inside cabin while driving or stationary. Just replaced valve cover gasket and odor still persist? Also a ticking or tapping noise coming from the rear possible fuel filter /pump etc? I’m getting ready to change cabin filter is that a fix? Thanks in advance any mechanic in Frederick, Md area who can help with cluster replacement?
(1) Answer
i'm willing to bet the breather system has a leak somewhere. check the hose at the back of the valve cover which may become gummy or brittle and leak. also check the breather hose where it connects to the engine block between the intake manifold and oil filter. look closely and use your hands to move these parts as cracks may not be easily noticed. there may be some oily areas around a breather leak. the smell of breather gases can be compared to the smell at the oil fill cap when opened after shutting off a hot engine. is the tapping noise from the left or right rear of the car? pump and filter are on right (passenger side), leak detection pump is on left (drivers side).