I think the check valve just got old and contaminated. Making the valve work by blowing and sucking on it (can you say bad taste). I did this without cleaning inside it, just wiped the oil away from the outer ring that the lips touched. I wanted it to be in the same condition as when it was installed. I found that it did not operate as smooth as the new one. It also seemed that small particles may have gotten in it. Those small particles were probably causing the valve to stick. I have not even driven the car since the "operation". It was a great day here so we drove the SL with the top down.

Dave

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1970 220D, owned 1980-1990
1980 240D, owned 1990-1992
1982 300TD, owned 1992-1993
1986 300SDL, owned 1993-2004
1999 E300, owned 1999-2003
1982 300TD, 213,880mi, owned since Nov 18, 1991- Aug 4, 2010 SOLD
1988 560SL, 100,000mi, owned since 1995
1965 Mustang Fastback Mileage Unknown(My sons)
1983 240D, 176,000mi (My daughers) owned since 2004
2007 Honda Accord EX-L I4 auto, the new daily driver
1985 300D 264,000mi Son's new daily driver.(sold)
2008 Hyundai Tiberon. Daughters new car