[Woodz428]

Didn't see the previous post (maybe I did,don't know), but in answer to whether Hydraulic lifters collapse the answer is YES. They make a hell of a racket as well when they do,like a loose mechanical lifter. It is virtually impossible to get them to pump up in a running engine as well. If it is a collapsed lifter,trace which one and replace it, once it's collapsed it will probably do it again. You should be able to tell which one by pulling the valve covers and turning the engine over so you can check each cylinder, the one that is loose is your culprit. It could be more than one.