I didn't use any lubricant or sealer on my 190 e 2.6 water pump where it attaches to the engine block. I did use some petroleum jelly on the o-rings where the tube attaches. My pump doesn't leak a drop.

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1990 190E 2.6
1996 Grand Voyager 3.3
1985 Mustang GT 5.0 5 SPD
1982 Suzuki GS 750T