Would a totally collapsed lifter allow enough clearance for the pushrod to escape the cups that hold it at both ends?
The instructions for checking the valve clearance is to bleed one down a lifter by pushing on it and then check the clearance between valve and rocker for betwee, .060 and .210. I assumed this was with the lifter totally collapsed. That isn't enough space for a pushrod to escape.

If it was caused by collapsed lifters, are new ones required or can the old ones get back on their feet?

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13