Art, we are getting restriction on return fluid or possible vent is too small for hydraulic flow
returning back to hydraulic tank. Next thing making a heater from your hydraulic system,
Looking at your hydraulic fittings coming off hydraulic pump and off the motor driving fan.
Where I'm going, connecting into new replacement hydraulic pump possible add on fittings
to connect up present hoses. Possible the ID. of hose fitting is smaller. Pushing hydraulic fluid
under pressure and pump has more volume than pump that failed ( now comes the back pressure )
and heat on return to tank. Relief valve that dumps pressure could not set up to correct pressure
and set to high. I am asking lot of questions but feel problem is, too much flow into fittings
that have smaller openings, too small hydraulic hose to handle present flow creating back pressure
In return back to tank. What you told me today extreme heat is being generated and above
is what is causing extreme heat. One thing, readjust relief valve which is part of this problem remove
castle nut on relief valve and turn outward 3 turns CCW and lock back down. The heat should be
cooler. In troubleshooting problem the use of a pressure gauge will not pickup on problem,
where a hydraulic flow meter will read hydraulic gallons per minute, hydraulic back pressure and
Fluid temperature. What your going find is a restriction in your system. Ran into this kind of
Problem several times with hydraulics. Last question is your hyd fan motor condition, a person
can tell if motor problems by removing the 3rd hose on motor body ( this is called motor case drain,
And you have stream of oil coming from this point you have a problem with fan motor. )
Dave Atherton Retired Cat Mechanic