Describe how the manifold gauges and the 3 hoses were hooked up to the car/ vac pump and direct to vac pump . Include both valve positions. You have a leak somewhere.

I say don't take it to a shop, because you can't claim DIY anymore and you learn less.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked