Pulsating and fluctuating cat pump.

[platoridge]

I have a Cat 5cp2120w pump on one of my self serve bays that started pulsating a few days ago. Today I replaced the 6 valves to find the back up rings were melted. Now its still pulsating and fluctuating (going back and forth from 500 psi to 1000 psi.)
I again took out the new valves to see if any of the old back up rings were caught in a valve; Nothing found. I ran water through the pump while the valves were out to "rinse" any dirt that might be in there.
I removed the head to see if the pistons were cracked or the o-rings were bad but everything appeared fine. I replaced one locking swivel that was looking a little shady.
But, its still pulsating / fluctuating! Is the pressure regulator the next step?

 

[MEP001]

If the backup rings were melted, most likely the low-pressure seals will be too.

 

[cleaning up mud]

the head is most likely washed out, you have a one time replacement from cat for a 5cp.

 

[I.B. Washincars]

My experience with washed out heads has been pulsating. The pressure pretty much stays steady, just the pulsating in the hose/plumbing. I don't think a 500 psi swing is from washout.

 

[MEP001]

No, and it usually runs fine for awhile after replacing the o-rings and will start to pulsate after they've blown out.

 

[platoridge]

When I said melted, it wasn't nothing like this mess!

 

[platoridge]

What do I look for to see if the head is "Washed out?"

 

[I.B. Washincars]

Check out the "Sticky" thread, labeled 310 Manifolds.

I may edit the title so it will be more explanatory.