Sorry to resurrect this thread but if anyone wants to know I recently bought an EFFBE repair kit for my 617 vacuum pump. It had the thin check vlave o-rings which didn't work. I replaced them per this thread with the original thick o-rings and fixed the problem. The original failure was due to a check valve diaphragm which cracked.

Do not use the EFFBE repair kits...

Jim
'82 300SD