I recently bought a well used Komatsu PC40MR-2. There are a few hydraulic drips that I am working through. The issue is a ticking sound from the area at the back end of the motor where the main hydraulic pump is attached. The person I purchased it from said he changed the hydraulic fluid and filter. I have adjusted the valve lash when I first got it. A master mechanic friend said it sounded like the injectors so I bled those by loosening and tightening them one at a time at low idle. No help. Google says it could be several things in the pump. The fluid is full, I have bled, or attempted to bleed the air from the hydraulic pump. I'm not sure where to go next. Any insight would be appreciated.
If the valves are set and none were way out of adjustment, have you cut open the engine oil filter and checked the paper to check for metals. If there is none maybe your problem is coming from the pump or pump drive. Cheap things to check before diving into it. Did you get to see the hydraulic filter and the paper media inside of it. That is what I would like to see. Start with engine filter first. Simon C
this likely is not the problem... but the isuzu engine in my mini would make a popping/cracking noise around the 1600rpm range. Turned out to be a shield between the exhaust and the pump since that's how Deere routed the exhaust. I took that shield off, welded it along the crack and put it back. no more noise. So... I guess check some other simple things in addition to what Simon says.
Had a Toyota Camri years ago with the exhaust shield rattling like you mentioned. New shield and no more noise. Simon C