Here's the o-ring that you need - sold through this web site: http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=25D0QUJAO26V1DT5OA&year=1986&make=MB&model=300-E-002&category=A&part=Timing+Cover+O-Ring&appEngines=10-002577-

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1986 300E (3/2002) Rear ended and totaled (10/2009)
2000 Xterra (5/2000)
1992 400E (11/2009) -Sold
1986 300E (12/2009) - Sold
2004 E500 Wagon (6/2013) - Sold