The aux water pump from my '88 started leaking.
#1 pump in the pic is the original unit. I replaced the O-ring,
sealed the interior seam with RTV and "upgraded" the fasteners.
It still leaked.
#2 pump is one I bought at Hershey this summer since I knew
the original unit was on its way out. Bought bunches of parts on
eBay, never had a problem. Look the guy in the eye and shake
his hand and get sold junk. The electric motor is failed.
Doesn't leak though.
#3 pump I bought from my local Porsche junk yard guy for $90.
It''s very, very quiet. I was not aware they updated the pumps
on the later cars.
I'm getting very good at removing & installing these without removing the intake!

 

i had good luck with resealing mine with rtv. I coated the inside seams and a light coat on the old o-ring and its holding up great

 

One of mine is a little noisy, is there anything I can do; or just plan on replacing it? Bruce

 

The impeller housing on the supersceded version seems
to be much more beefy than the earlier version.