Ok, Probably everyone knows this.
When I first took off my 300TD cover I marveled at the rubber gasket thinking that unlike the cheap cork ones..I can use this again! When I adjusted my recently acquired 300D's valves and noticed it's gasket was brittle and cracking with the slightest bend
I pulled out a used one I had....still felt soft and looked good.
But...after installing it, the thing leaked like a sieve!
I applied a .0025" feeler gauge and managed to easily slip it between the seal and the head at engine rear. Mercedes limits the amount of squish with bosses on the valve cover, so depending on the flatness of your cover and head surface there is just so much available compression of the rubber seal.
.....so just pay the man the $10 for a new one. At least there is no scraping involved

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