1988 528e thwup, thwup, thwup noise at low speeds

["teborden2" <teborden2@xxxxxxxxxxx>]

This forum is by and large terrific... am learning a lot about heating system,
drive train noise, cylinder heads and things that go clunk.

When my v-hicle runs at low speeds (5-25 mph, say), I hear a mild flapping
sound emanting from mid dash/auto tranny vicinity.  Have had the noise for
35,000 of the car's 130,000 and it's consistent.  If it helps to know, along
the way I have replaced engine mounts, guibo, center support bearing.

Is anybody familar with the possible source? Did I once read that it could be
a warning sound when the catalytic or oxygen sensor goes?  I replaced sensor
myself back at 96,000.  Sound was there before and after.

Thanks.

Tom Borden

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