@H2O MAN,
I tightened the tri-guard too tight and cracked it (STUPID - tighten slooooow and when it begins to get tight, turn only enough further to align the brine refill nuts). Purchased a used tri-guard, a new brine injecter w/ o-rings, a new poppet assembly and o-rings for the piston. I figured I might as well replace the piston o-rings while I had it apart. I found the bottom piston o-ring was pinched outside its groove on the piston (I assume this was part of my problem and an indication I will need to replace the valve body or whole head unit in the near future). It's back together now - no leaks. I ran it through all valve positions in service mode without any issues. The tri-guard did have water running through it during this and appeared to be working properly. I just started the cycle and we will see.........
H2O MAN, I assume you will be able to assist me in replacing my Q2 valve with a Fleck 2510SE in the future? Thanks!