Cat 310 issues

[QuickshineCW]

Hello everyone, I'm looking for some insight on this issue with a pump for my Self Serv. Out of the blue I started losing pressure and was getting some knocking or chattering in the pump, so I ordered a full kit for the front end put it together and had steady pressure but still a very light knocking sound. I figured it must be some minor air/cavitation so I replaced the unloader/bypass valve and checked all of the inlets for the water supply. The pump draws from a tank below and the float valve keeps up fine.
Now the real problem, completely at random on any high pressure function the pump slows way down and starts slipping at the belt. Will come back after like 45 seconds like nothing ever happened!
Possibly a main bearing or something else I'm missing? I am totally ok with buying a new pump but I would hate to spend $800 and it was something

 

[MEP001]

Now the real problem, completely at random on any high pressure function the pump slows way down and starts slipping at the belt.

Tighten the belt.

 

[Greg Pack]

Reassess after tightening the belt. Could be something internal. A couple Years ago I had a Cat pump throw a rod and fracture the side of the case, dumping all oil out. Even with a broken rod and no oil in the crankcase It was still running and producing pressure, just pulsating a little.

 

[QuickshineCW]

Will try this and update if anything changes!

 

[QuickshineCW]

So I finally got around to tightening the belt, it wasn't exactly loose but I used a bar to put some more tension on it and will hang around to see if I still get slippage.