Sorry I can't answser your question. I assume the check valve is the PCV valve? I have heard that if the PCV valve goes then you get what you have there. I don't kave the Kompressor so I don't know much about it. My friend has the '99 C230K. He asked me to find the PCV valve and I looked around the engine compartment and didn't have a clue. I am interested also since he needs to change his as preventative maintenance.

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra