Low oil pressure can also keep a lifter from pumping up.  Go to 20w/50
if you are not already using it, it helped keep my lifters from bleeding
down overnight.  Hydraulic lifters work by oil pressure filling the
space between the lifter body and the piston that is created when the
internal spring takes up the slack in the valve train.  Oil is not
compressible, but it can drain down if the engine is stopped with cam
lobe holding a valve open.  This is the most common cause of the morning
tap tap tap, and usually they pump right up again.

You are better off using these fixes rather than replacing the lifters.
It is always problematic to put new lifters on an old cam, especially a
VW flat four cam where the lobes do double duty.   If you do, use
assembly lube on the lifters and run the engine at 2000 rpm for 20
minutes to "wear in" the lifters.  2000 rpm keeps the lifter "floating"
off the lobes rather than keeping full valve spring pressure on them as
exists during idle, which can lead to galling of the lobes.

Good luck, I have 200,000 miles on my original engine using these
tricks.
--
Stuart MacMillan
Manager, Case Program
800-909-8244 ext 208

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