C-5's are known for the cowl drains to fill with debris and then the
water from rain storms or washing that would normally drain from the
cowl builds up and it will eventually flood the wiper motor assy and
it usually ruins the entire assembly. So replaceing the wiper motor
might fix your problem for the time being but next time your in the
rain same problem again. So you have too keep the cowl drains cleared.
the drivers side has two drains and they can be reached from the
engine compartment if you just feel around with your hansd sort of
under and to the rear of the hood latch. the passenger side I cant
reach them so I have to remove the pass front wheel and then open the
access panel in the lower rear section of the wheel well. Inside you
will see the rubber tubes coming down from the cowl. the end of the
tube has slots in it to allow them to drain. Clear the debris from
them. If you have never done this then start with the pass side that
way you can see what you will be feeling around for on the other side.

there is also a similar drain on the HVAC system that likes to plug up
if it cant drain then you can flood the cars fuses and computer with
water, because they are located right under where the a/c water drains
to if the usual drain is blocked this drain is harder to get to
because of some electrical wiring and the passenger side exhaust
manifold limiting the space. the drain sticks through the fire wall on
the passenger side by the exhaust manifold. I was able to get to mine
from the botom of the car.I used a razor knife to slice the end off
the drain valve so it would not plug up any more. the reason I did
this was when I bought a 2004 spiral gray coupe for the wife, I saw
that GM no longer used a closed off drain valve there it was just a
rubber elbow to direct the water down. Mine is a Navy Blue Met. 2001
Convert. M-6   2 vettes for every garage.