Hey there, we have a ~1990s Sumitomo LS-1600FJ2 excavator with about 5200 hours. It was sold to us on Facebook as a Link Belt 1600 CII (we found out later it was a grey market machine) with a bad pump and a box of parts. The guy we bought it from had tried to put the pump back together but couldn't quite get it. We were able to get the pump that had gone bad replaced (UCHIDA-HYDROMATIK A10VD43SR1RS5-992-1) with the parts he sent us home with, but he never gave us the old pump to inspect. After that its been nothing but issues. We did change the hydraulic fluid and air bleed to see if that would help. Right now we have two definite problems: 1) the tracks are very slow and weak. They will rotate when the machine is lifted up, but when weight is on them they are very slow or stall in forward or reverse. If you use both controls in tandem, you can get the machine to move slowly, but using just one track to move or turn is hit or miss. 2) the blade sinks down quite quickly.. We thought it was cylinder seals, but when we disconnected and cap the cylinder, it seems to hold itself. Interesting when we move the tracks back and forward the blade sinks down more rapidly than when we leave the controls in neutral position . The blade does lift the machine up, but if you leave the controls alone, it sinks by itself as if some slight pressure or a leak is causing the blade to be forced down. Also, the machine has to be run at maximum throttle for any functions to work, otherwise at lower throttle the digging functions seem to have no power. Is this normal? Our running theory is the main control valve is bad, or something with the rotating joint. Most of our previous experience is with gear pumps and open center in tractors not these variable displacement swash plate pumps, so we are second guessing ourselves. Finding parts has been next to impossible it seems. Most items discontinued or unavailable according to dealers. Thanks for any help you can provide. Jon
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