Rebuilding Hydraulic Lifters
This video shows the disassembly, cleaning, and rebuilding of hydraulic valve lifters. These belong to a VW 16V head but many are similar. A couple of these could be compressed by hand when they came out of the head. I decided to rebuild all of them. This takes a long time so you might want to consider just buying new ones, but if you have patience and don't mind the work, it's very rewarding.
remove/install hydraulic lifters without removing engine or head
how to remove/install valve lifters without removing head from engine
Replacing a hydraulic lifter on '86 Mercedes 190E
Can Follower tapping aka hydraulic valve lifter.