Case 580 ck extendahoe Hydraulic

A friend has the backhoe and had pump go bad. I got him a new replacement pump. I pulled the old TRW pump apart and found the pressure plate and seal had a 1/2 inch chunk missing. He just called and said pumps bad. I think it's a problem with where the old pump parts went. What should I have him or us check? Could the loader control valve be blocked?

Case 580 ck extendahoe Hydraulic