Coming back from a 2 hour drive today as was driving through my neighborhood at around 20 MPH noted a faint "tapping" noise. Got to house and let idle - tapping coming from injector side of engine most noticable around first third (#1 or 2 cylinder) of the head.

Strangely it taps consistently and faintly, but noticeably, for about 30 seconds then cleanly stops, then starts again for another 30 seconds ... follows engine speed but not noticable as the speed increases as the engine noise covers any potential noice ...

Was thinking lifter? But, why would it cycle ...

Anyone had this happen before?

Thanks!

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George Stephenson
1991 350 SDL (200K and she ain't bent, yet)
former 2002 E320 4Matic Wagon - good car
former 1985 300 CD - great car
former 1981 300 TD - good car
former 1972 280 SEL - not so good car
a couple of those diesel Rabbits ...40-45 mpg