It sounds like it is the end......of your vacuum pump.

When it begins leaking it will pump oil vapor into the intake manifold which would cause the car to smoke and run roughly, and make your brakes not work. Try hooking up a vacuum gauge to the main line coming off the pump. You should get in excess of 20" (I think, can somebody confirm this).

Re-build the pump before you drive it any more. I have heard of them dumping their guts into the timing chain, which will totally ruin your day.

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine