Noisy hydraulic lifters

[gfl@cc.bellcore.com (grant f lenahan)]

re: lifters

The hydraulic lifters in Audi 5-cyl engines are notoriously
noisy - but work just fine that way.

Most cars will tap some when cold, particularly if the car has
not been driven for 2+ days.

However, I've put megamiles on engines with original lifters,
and ones that tapped to boot.

Since the lifters operate on oil pressure, the oil drains out of them
at shut down.  The better oil filters (Mann, etc) have a valve that 
keeps oil from draining backward through the filter.  Fram, purolator,
etc do not.  HOWEVER . . . I used Fram for 150k+ miles with no
consequences in my last car.  Tapped at startup, then ran fine,
for a LONG time.

If the noise concerns you, DO use the german/audtrian filters,
but I wouldn't spend $500.-+ to fix anything until more
serious symptems (eg: lost power due to reduced lift)
showed up.  I can;t see where it will do lasting damage,
anyway.  Others?

Grant
gfl@cc.bellcore.com