I had my air filter housing off tonight and took off the two breather hoses to clean them out. The breather hose that connects with the air filter housing and goes to the passenger side valve cover has a little copper pipe (internal diameter of about 1.5mm). It inserts in the breather hose (part #116 094 0791) in the side. It has some white crud in it so I cleaned it out too. Where does this copper pipe go? It seemed to run under the fuel injector and I couldn't see it after that. Also, what does it do? I still have my rough idle after cleaning all these parts out. No choice now but to turn it over to the pros.

Thanks

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Jason Priest
1999 E430
1995 E420 - retired
1986 420SEL - retired

That hose is supposed to be plastic...It goes down to the fuel pressure regulator. Its purpose is to give fuel a place to go in the event the regulator diaphram fails. If so, the fuel will go into the crankcase and not on the ground or worse a hot exhaust manifold.

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Benzmac:
Donnie Drummonds
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS