I replaced the black plastc impellar pumps on 2 1995 V6s. Both were prior to disintegration, and one had cracks. My theory is that Ford molded the impellars from glass filled nylon. What got to the pumps over time was the water. Nylon has great properties, but will degrade over time in the presence of moisture. I think the term is hydroscopic. The white plastic could be one of many newer polymers,(maybe not as cheap and easy to mold as nylon) and never have a problem. I replaced mine with the GMB DuroPro metal impellar type from NAPA, yet NAPA's standard variety has the white plastic and costs more.
