<< IMHO, this is really a non-issue.  If a water pump shaft seal lasts long
 enough for cavitation to cause erosion on the pump impeller, you have gotten
 you money's worth from that particular pump.   >>
 AH! yes indeed..except most people don't replace the pump they just replace
the face plate and impeller. the housing (the WHOLE pump) is the part that
wears. It's the BACK of the pump, the aluminum part on the block, NOT the
iron/steel impeller!
In it's life the van may have had 5-6 pump "faces" on 2 or 3 different engine
blocks..all with the same housing!...So, my point, if I may reiterate, if you
have reason to have the engine our or apart enough that the pump housing is
accessible ..it's time to replace the pump and if you are JUST doing the face
plate and impeller, CHECK the housing!
Your point about the nature of the cooling system in general gives all the
more reason to do this..

Or do as you darn please and I'll get *another* diesel westy cheap..  ;-)

BTW, anyone have an upper hose for a 83 diesel?..yes THAT hose..and no, DON'T
ask....  :*)

steve

"Hey! nice Jeep, Mister! "
"Look kid, it's NOTAJEEP! "