I too have had bad experiences with the aux water pump on my 84 190E. Okay, parts wear out, but when the replacements are consistently bad, I get annoyed. (But since I have owned a slew of British roadsters, I am used to it)

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Patrick Leber
'84 190E 2.3
'83 Porsche 944 (track car)
'84 Porsche 944 (parts car)
85.5 Porsche 944 (sled)