One thing (among many) to suspect is the viscofan operation. My manual states, "Temperature-controlled viscous fan couplings must be transported upright. Fot brief periods e.g. for installation purposes, the couping may be placed on the flange side, but never on the front side".
It also states, "The bimetal strip must not be bent or damaged".
I take this to mean they may no longer function properly.
My question would be, if one of the above occured during the first pump replacement, could that lead to a mistaken belief that the pump failed?
Just a thought.
86 300 SDL