Hydraulic Lifter Noises

Replacement of hydraulic lifter cartridges - IF noisy, sounds like a bucket of ball bearings rattling around, at startup after sitting for a day or two; if car sits for an extended period such as a month and the sound presents on the first startup but disappears thereafter and does not return on a subsequent restart this is a sign that the lifter cartridge seals may leak a bit but have not progressed to the point where cartridge replacement is indicated.

This seems to be a chronological age-related issue as the cartridge seals lose elasticity and slip off causing the cartridges to no longer retain their oil or proper function at initial start-up. This issue presented for me about the same time as the need for clutch replacement at 80k miles on my car.  Replacing them involved removing the valve covers and presents the opportunity to replace the valve cover seals, plugs and wires at the same time incurring minimal additional labor to do so.