It’s not difficult to rebuild centrifugal spray pumps like the Hypro pumps used on many farms. But there are things that ease the process:
- Before disassembly, use a center punch or scratch-all to mark both halves of the housing so you can maintain the correct orientation of the discharge port in relation to the pump’s mounts when you bolt the two halves back together.
- A conventional seal kit provides the basics to rebuild a pump: ceramic seal, gaskets and o-rings. It’s not a bad idea to replace the impeller at the same time, especially plastic impellers. The narrow little vanes inside plastic impellers wear at their tips. Also, the tapered nose of the impeller where it fits into the flare of the inflow housing must be a close fit. Damage or wear to that nose can impair the pump’s performance.
- The fast way to remove the old ceramic seal is to break it with a punch then remove the pieces. Be careful when prying out the fragmented ceramic seal to not mar the surface where that seal sits in the relatively soft cast iron housing. Ceramic, especially the sharp edges of broken ceramic pieces, is harder than cast iron.
- Follow instructions included with the seal kit about whether to assemble the ceramic seal “dry” or to use light oil between the lapped (super-smooth) surfaces. Don’t guess—depending on manufacturer and design, it must be either completely clean and dry, or lubed.
- Lube all rubber O-rings with petroleum jelly or white grease to reduce chances of damage during assembly.
- Do not over-torque the acorn nut that attaches the impeller to the drive shaft. Ten to fifteen lb./ft. is usually enough. Blue Loctite isn’t a bad idea.
- Final tip: to minimize future leaks due to corrosion, grease the threads of the small square-head air-bleed bolts before installing them in the cast iron housing.
