Take look at the picture and tell me what would cause this. It is the brass(?) valve (one of two) that directs the flow within the hydrulic pump. When running the machine it will noisily let pressure by back into the return. Replaced this on pump 2 a few months ago which fixed the issue. Now it came back and both valves on one and two pumps are pitted out this way. This is getting expensive fast, with no apparent cause! The swing has been giving issues as well, so we are pulling the swing motor apart to find what is causing it to be weak after it warms up.
Don't know the cause but I'd diagnose the issue before throwing parts at it. Your system is probably contamented now and needs filtered.
First glance...restricted case drain.
Case drain? Elaborate please!
I just don't have a clue what would cause it to pit out like that. When the 1st one went bad we thought maybe it had gotten too hot at some point, or maybe even a factory defect in the material. But now since both have gone bad in a short period of time, there must be something causing it. An idea is that the swing motor has been putting metal shavings into the system. Which is why we are going to pull it in the morning to take it apart. Over the past 6 months the swing has gotten weaker and weaker.
What do the slipper shoes look like? Damaged too? From here https://www.machinerylubrication.com/Read/748/hydraulic-pump-motor-case-drains
Are you using zinc free hydraulic fluid? When I worked at Deere, they were constantly harping about the negative effects of zinc on yellow metal parts. I doubt it would cause that much damage in such a short period of time. I’m also going to have to say inlet vacuum or high case drain pressure.
I would say oil with very high moisture content.
I would call that a seal plate and believe it rubs together with the piston and barrel assembly. You can't just change that part without lapping it together with the piston and barrel mating surface. Any damage on either surface will cause those two parts to chatter when high pressure forces its way through the defects going back to the lower pressure side. How many hours are on the machine and pump.
Ive been using Cam2 aw hydraulic oil. Probably not zinc free...
I think that's the same outfit that has a pending lawsuit against it for dodgy oil. Maybe not necessairly the particular oil you're using, but still............
We pulled the inlet screen for the 1st time today. It was pretty clogged, and coated with black residue. Also pulled the swing motor apart, the piston and cylinders look alright. No scarring or scratches. So were pulled out the cross relief valves, one again nothing bad wrong there. But were going to go ahead and replace a few of wear items related to them. So at this point, it looks like the screen was causing restriction and causing these valve to pit out? Would also explain why all hydraulic function are a little slower then most.
Well we changed the oil out a few months back when we first replaced this valve piece. And sense then weve had the oil plenty hot at times to boil any water out. The machine runs on the hot side if your working it.
Close to 10k on the machine, assuming the pump has the same. When we pulled the pump apart last time we fully inspected it and the only thing that we could find wrong was this valve (or seal plate). At that time, the valve on pump one was in perfect condition. We only replaced the valve on pump 2.
Yeah for their 303 line of oil.
Those wafer(valve) plates can be damaged due to cavitation, but that is severe. Is there a charge pump on this machine and if so, what is the charge pressure?
It does not
If there is no charge pump and it depends on some kind of head pressure to supply the pump, then the oil type is critical and also there can be no supply(suction) restriction. I would only use the oil that the manufacturer specifies
If I'm remembering it right those hydraulic reservoirs are supposed to be pressurized. Not uncommon for the pressure relief valve/vent on top of the tank to stick open so that there's only atmospheric pressure working on feeding the pump.
All the excavators that I know of now days uses the up and down movement of oil in the reservoir to pressurize air above the oil to about 15 PSI. The cap on the reservoir is like a radiator type cap that allows air to be sucked but not let it out. Many brands of excavator use a dedicated valve with a filter on it for clean air going it.