S4 and S5 N/A water pump and housings
 

Is their a diff between the S4 and S5 water pumps and housings? Do they both use the shims? I have both types in the garage and only diff i see is the S5 has the fan sensor on it also. Are the water pumps interchangable? The parts store list them with diferent part #'s.. Thnaks for any help

The water pumps are not a direct swap. The S5 pump is a better pump designed for a bit higher RPM. It also has a larger pulley meaning it'll spin at a lower RPM than an S4 pump. An S5 pump will fit an S4 motor if you grind some material off the front cover and the pump body. Without doing this they make contact at the bottom and won't seal at the front iron. As far as I can tell the thin shims are used with the S4 irons only. Meaning that if you use an S5 pump on an S4 iron you'll need the shims. If you use an S4 pump on an S5 iron you don't need the shims. That's just my own thoughts and have never had it proven otherwise.

Just re-read you post. If you're looking to buy just a replacement pump you're better off getting the correct pump for you model. To swap pumps you'll need the housing and upper neck that goes with that housing. Not something you're going to pick up at your local parts house.