remove the pump. next throw the center bolt away that came with your rebuild kit and reuse the old one. The one in my kit was short by 1/2 inch. You need that 1/2 inch.Have a friend compress the springs while you tighten the center bolt on the pump. they say you do not need anything on the gasket which does not come with the repair kit but why not a little gasket seal?

Check valves . If you forget while you are changing them out they go Right one crown down and left crown up.
I hope this does not add to your confusion.
One more black and stormy doctor

during my process, i didn't notice where one of the plates was during removal. attached are pictures of my reassembly process--does this look right? especially pic #2? and convex side of diaphragm to the front of car? thanks! (i'll post more pics as i get this reassembled.)

Attached Thumbnails

       

__________________
1980 300D (non-turbo, 421k miles)
1984 300TD (turbo, 305k miles)
1985 Vanagon (170k miles)

Vacuum pump diaphragm replacement pix

__________________
Sonny


86 190D N/A 2.5L Auto 265k "Ruby" -Sold-
79 300D 242k "Condi" my first -sold- RIP
2013 chevy sonic hatchback - had to for work

thanks sonny--
so it looks like i've got the plates right--after checking convex and concave "out," i liked concave. also wondering how much to torque the center bolt?

__________________
1980 300D (non-turbo, 421k miles)
1984 300TD (turbo, 305k miles)
1985 Vanagon (170k miles)

do not over tighten!

__________________
Sonny


86 190D N/A 2.5L Auto 265k "Ruby" -Sold-
79 300D 242k "Condi" my first -sold- RIP
2013 chevy sonic hatchback - had to for work