I have the W123 series on CD and I can't find a diagram of the vaccuum system. Trust me, I looked since I have a engine shut off problem with my '83 TD. The manual tells you how to troublehsoot, but no actual diagram. I found a diagram in my Haynes manual of the central locking system, but that was it.

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member