I always use the gasket and a thin application of sealer on BOTH sides of the gasket and always make sure that BOTH surfaces are clean. I HATE doing a job twice. But I have on many occaisions which all lead to experience NOT to do THAT again.

I hope you didn't reuse the old gasket? that is a no-no too.

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1986 Euro 500SEC "RUF" 9:1CR, "Rose"
1985 Euro 500SEC Cabriolet AMG Widebody
1982 Euro 500SEL "Blue"
2001 Texas Heeler (Aussie/Queensland X) "Sulphie",
2012 Queensland Red Heeler "Squeak"
Best dogs I've ever had.