I looked at all the cat 310 repair parts at KR and I could not find those O rings. Thanks a bunch for the links!!!You can get the o-rings from Kleen-Rite. They're pretty cheap, it's the backup ring that's really expensive.
Buna-N Seat O-Ring for 5 Frame Pumps | CAT Pumps | 43358
The CAT Pumps 43358 Valve Seat O-Ring is a nitrile seal that replaces the existing valve seat o-ring on 5FR pumps.www.kleen-ritecorp.com
Back-Up Ring Repair Part | CAT Pumps | 48361
Use the CAT Pumps part 48361 to swap out a worn or malfunctioning back-up ring on your model 310 or 5CP2120.www.kleen-ritecorp.com
These parts are metric - you likely won't find them cheaper unless you order 10,000. The backup ring can be reused as long as it looks perfect, especially where the ends meet up. They would have to be custom-made and won't be cheaper. I tried to find a Parker Parback ring to fit but no one has been able to find them in the right size and thickness. I feel like that might hold up a little better and would also be less expensive.
I'll take it apart again and make sure all the backup rings are on the bottom. Maybe I'll just use some old rings till KR decides to ship them to me with 15 bucks shipping.There is a special tool, but even that will damage the seat if you don't get it just right. Try putting the plastic top back on without the spring and poppet and pull straight up gently with needle-nose pliers while moving it in a circle.
It sounds like the manifold is washed out. The o-ring or backup ring will hang up in the eroded groove. Look in the manifold where the o-ring should seat and see if there's a groove. There's lots of info and pictures here:
Washed out 310 manifolds - With pictures
Odd to hear the Arimitsu service is better than Cat. Just curious...of the 20 Arimitsus how many were purchased? I don't understand why you feel it is odd that they have better service. Actually, Cat didn't place the bar very high. They seldom, if ever chime in here to help out. James (no...www.carwashforum.com
The backup ring goes on the bottom if the valve is sitting upright on a flat surface. I dip the assembled valve in oil before I install them to keep from cutting the o-ring.