Make sure the diaphram in your vacuum pump is not leaking---engine oil will get into the intake manifold by way of the return line to the manifold and cause rough running, smoke, and a noticable increase in foot pressure to apply brakes (because of decrease in vacuum to the brake booster). Best way to check is with vacuum guage; however, you can also remove the vacuum return line (line that goes to the intake manifold) at the vacuum pump and check for engine oil at the fitting. If you see black engine oil, you have a leaking disphram.

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K. Weimer
300SD (1)
300D (5) [Plus 1 parts]
300SEL 4.5 (2)
280SE (4)
280 (2)
250 (1)
250SE (1)
240D (7) [Plus 1 parts]
220D (11) [Plus 3 parts]
200D (2) [Plus 1 parts]
180c (with sunroof)

1995 Nissan UD1800 rollback
"If I can't fix it, it don't get fixed"