Just purchased my first excavator, have run them for years for other people and decided to start out on my own... Bought a 1996 John Deere 160lc that has know hydraulic issues.. Previous owner said when weather is cold out like in the winters here in Oregon machine runs fine but as soon as warmer weather comes the hydraulics start to slow down... In warmer months it is fine for the first hour of operation but then slows down... I know a little on hydraulics , so I know that slowing fictions are usually cause by hydraulic flow issues so wondering why temperature is affecting the speed or flow per say? It has had filters changed multiple times and tank flush with fluid change also. If anyone can help I would appreciate it gonna start with seeing if there is a cooler somewhere and then maybe take a infrared heat gun to look for internal bypass issues.. Please help with any other ideas thanks
Some generic stuff: The cooler is in front of the radiator, common problems are air flow plugging, missing foam/rubber seals around the radiator, slipping fan belts, debris trapped between the cooler and the radiator. Some other things to check would be if the correct hydraulic fluid is being used, and pump settings are correct. Possible causes of excess heat would be internal bypassing of seals in cylinders, swivel joint, swing and travel motors, and especially weak relief valves that allow frequent bypassing of oil at high pressure. It sounds like the oil is thinning out and as it gets thinner it leaks more internally, which creates more heat, it's a bit of a death spiral at that point.
As lantraxco says, first things first make sure its the correct grade of oil. This is essential because there'll be a bypass valve in the return piping. When the oils cold and more viscous, the valve opens at a set pressure, usually around 4 bar, and lets the oil flow back to tank. When the oil heats up and thins out, the pressure will drop and direct the oil through the cooler. Another thing to check is the bypass valve itself. Remove it and check the springs ok and nothings sticking it open. But the most common issue, again like lantraxco said, is the cooler itself and the seals/foam that surround it and the airflow through it. If you get it right up to temp, say around 70 degrees C, check the oil going in against the oil out to tank, at full rpm i'd be happy with around 8-10 degrees C of a difference.
Usually when I diagnose excavator issues it is best to do a cycle time test and see if all functions are affected. I worked for JD for 16yrs. They have specs for each function. This will help determine if problem is isolated to a particular pump or is it in certain functions. Also are the pressures up to spec. they are gonna be up near 5000psi. Just some other questions, how is the tracking? Does it go strait? does the 2 speed work? Does the auto idle work. Wish you were near I still have an old Palm pilot that JD/Hitachi used to hook up the hydraulic system to check and adjust hyd. and engine rpm. That brings up another question is the engine going to the max rpm. The hydraulics will automaticly slow down if it is not seeing the rpm out of the pump speed sensor located in the hyd. pump it is in the front right corner if your looking at the pump.