Spectra Watermakers Clark Pump Check Valve Cleaning

 I was having issues with my water maker, and Spectra Watermakers suggested I check and clean the check valves in the clark pump. The thought was that there may be something caught behind one of the check valves. There are four check valves; two on each side under the cylinders where they attach to the center body.
Here's how I did it.
My watermaker membrane housing and clark pump was located under the boards of the aft bed. To remove the clark pump, I closed the sea water intake and removed the two low pressure hoses and the two high pressure hoses. Then removed the four screws holding the mounting plate and then the clark pump can be removed.

To the right is the clark pump removed and ready for disassembly. I first removed the the base mounting plate held by four bolts. That helps with with allen key use of the allen head bolts at each cylinder end where it joins the main body in the center.

Undo the four allen head bolts at one end and carefully rock the cylinder to remove from the center body. There are three O ring seals; two around the check valves and one around the large round locating piece that has the piston rod going through the centre. The piston rode pushes against the white plastic looking piston in the cylinder.

Using a Q tip cleaner, insert to clean the interface of the top check valve against the seat of the valve.

The lower check valve can be removed with a pair of needle nose pliers. It's the one that has a cross piece. There are washers and springs which full apart, but it is easily assembled and placed back. Clean with a Q tip as well before re inserting.
Make sure all O rings are in place before presenting the cylinder up and reapplying the four allen head bolts. Repeat for the other side.

In my case, I found no debris around the check valves, but found instead the piston rod that drives the pistons to be badly corroded. You can see the surface eaten away on the picture to the right. This has seals that runs on the surface of that piston rod, and I suspect that is where my problem lays.  The unit has been returned to Spectra Watermakers in the USA