From my CD manual it says

"On engine 6125, the pressure relief valve is screwed in or on, respectivley, main oil duct at engine face and on engines 616/617 at oil pump."

"If the is no oil pressure or if the pressure is too low, check whether oil pressure relief valve on oil pump has dropped or become loose. In both cases, coat threads of oil pressure relief vavle with sealing compound, part No. 02 989 94 71 and screw in."

Good luck
Don

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1980 300TD-T (82 Turbo and Trans) 159,000 Miles "Jackie-O"
1983 300SD 272,000 Miles "Aristotle"
1987 Jeep Wagoneer Limited - keeps the MB's off the ice and out of the snow
1994 BMW 530it