Water Pumps - 986 vs 987

[Deserion]

Clearly I think there has to be a difference for Porsche to use a different part number without superseding the old one. Visually they look identical, to me at least, but can they be used interchangeably? Both are readily available through Porsche or Pierburg.

996-106-011-57 versus 997-106-011-06

It’s not a cost or availability issue, rather I’m curious and figure someone here knows for sure.

[JFP in PA]

As the Porsche parts system specifically states not to use them interchangeably, there is probably a difference in the engine case where it fits, or some other small but significant difference that limits the later part to the later engines.

[Deserion]

That’s what I had figured, appreciate the info. Now my curiosity is sated.