Komatsu pc40-7 had a slow swing issue and lack of power in blade. I changed the hydraulic pump and it fixed the problem, but there was track deviation and lack of power in one track. Ran machine for two hours and the final drive locked up I tore it apart and found the planetary gears were tore up. I installed a new final drive/travel motor. I still have severe deviation and track has no power. I checked all other function cycle times and they are to spec except the arm. It is 2 seconds slow. The arm and the travel in question work of the same control valve and the same pump section. Cable linkage is fine, stroke of spool is normal. I swapped main relief valves with a known good one and no change. Please help me
First guess for the travel would be seals in the swivel joint bypassing. The arm could be a weak port relief, restriction in the lines, cylinder needs repacking (does it drift in either direction with the lever in neutral and weight on it?). What else works off the same pump section?
Doesn't drift at all. What is "weak port relief" That fact that it doesn't drift does that mean that the packing doesnt need to be redone? Nothing else works off the same pump. I did find metal shaving I assume from the old pump stuck in the relief valve for the other control valve for the boom bucket and right travel. Could some of that be restricting the lines?
Port relief valves are used at either end of some valve spools to allow an overloaded cylinder to move rather than overpressure the circuit or allow some metal component to fail. Some do get weak over time if they are often opening, the heat created weakens the springs, etc. Sometimes when you shift the valve spool the port relief will open for a second or two until things get moving and the pressure to move the load drops. The fact that the cylinder doesn't drift in either direction probably means the seals are fine. Sometimes you can have a bad piston seal on the back side of the piston and you don't get drift unless you have a heavy load on it, full bucket of mud or the like. Hopefully if there's any metal in the system it's finding it's way to the tank were magnets and suction strainers are catching it. Normally metal debris won't cause a restriction but it sure will cause a lot of damage. I'm still thinking that your travel issue is bad seals in the rotary joint that passes the hydraulics down through the center of the unit to the travel motors and the blade.
Thats just so much of a coincidence that I changed the pump and now the swivel is bad immediately.
Oh, okay, I thought you had the travel problem before you changed the pump. If it was fine before you changed the pump and defective after, my first inclination would be to suspect a bad section in the new pump, flow meter would tell the story there if you have access to one. Are the hoses, if it has hoses, from the main pump sections long enough to swap them? See if the problem changes sides or not?
They are not long enough to change to the right hand pump but I did change it to the swing/blade pump. Slightly better and I mean slight still a horrible deviation. Swing had slight slow down on the travel pump but not much.
The blade pump should be significantly less flow than the other two, so if it improved I would say you may well have a defective gear section in that pump. OR the suction strainer is partly plugged or some such, some kind of restriction on the suction side of the pump, but that should in theory affect all the pump sections at higher rpm's and there should be some unpleasant noise from the pump cavitating. Was the pump you installed new?
It was a reman from the komatsu dealer
I'm guessing it's warranty time, but without testing there's no way to know for sure. Does your komatsu dealer have a test stand for hydraulics?