I got called out on an excavator pump last summer and posted some photos of the mess inside. Owner complained that the Komatsu WA600 would not pick up the boom or steer. This one I had to pull on my own and tear down to assess. This pump has lots and lots of hours on the meter and I'm not sure it is original. The photos show the suction side of the gears and you can get an idea of how they start to eat themselves up. No grooves or the kind of damage that would indicate something went through it.
First photo is the pump complete. Second photos shows the center section of the implement pump and last photo shows the steering pump.
That is why gear pumps are often throw aways. Only the ends and couplers between sections are reusable for rebuild.
This one has bushings for the gear shafts but the clearances measured out at the end of their range. I don't have the adapters for removing and installing the new bushings so we are looking for an aftermarket pump right now. I'll know a little more in the morning. Komatsu has exchanges now for these and I was quoted a little over $10K for that and all the hoses and O rings to put all back together. I know from experience these pumps are not good for much more the 5K hours and this machine is not going to be a big production machine anyway.
Try www.flinthyd.com . If they cant do anything, they may be able to steer you in a direction.
Would the lack of paint be an indication that it had been replaced at some time in the past.? If it was original wouldn't it be painted the same colour as the machine.?
I don't recall that these ever had any paint on them when new. It does look like the suction hoses have been changed at some time in the past which is an indication that the pump stack is not original. The opposite pump stack has the transmission, torque converter and switch pump and might be original. It doesn't have any paint on it either and one of the suction hoses is just decrepit.
I'm trying to recall if the WA600 they have at the quarry had painted pumps. I know we had a problem with one or both of them pulling the threads out of the pressure hose side. I'd have to do some digging to see which pump that was on but recall we fixed that with some helicoils and that fixed it. Also we did have to replace one, again need to do some research to be sure which, but last I knew there was a new/rebuilt pump in a crate in the store room. That's another one of those things I have no idea if anyone even knows it's there! For some reason the pump above does not look exactly like the one on our WA600. Don't think the pump on the right side of machine had the small third section. "Right side being as you sit in operators seat"
Dealer used parts guy has a new one coming for about $6,500. I've got to go get the other pump out tomorrow. The owner had bought a bunch of WA600 parts at auction and had a transmission and switch pump in that bin. I'll bring that back with me and tear it down for assessment. If it's bad we will get another one of those. I talked to an operator who ran this for awhile about five years ago and said the transmission pump was putting oil into the engine. I had noticed that the engine was over full and the transmission was low. I'll take some photos of the tranny pump tomorrow when I get it apart.
Here is the other pump. The front and middle sections run the transmission while the last pump feeds both the steering and implements. The outlet goes to a demand valve that shoots oil to which ever function needs more oil. This was a used pump that came from a scrapped out machine years ago and I dismantled the back section to see if it was usable. If you look at the scratches you can see where it ate some material. Anyway this pump will end up in the scrap barrel. The Komatsu used parts guy in Missoula has a new pump sitting on the floor that is getting sent our way.
Also note that you can see brass on the end plate. That should all be a silver color. You can also see some black on the right side on the plate. That is where oil was bypassing and getting so hot it burned.
I seem to recall that for any of the hydraulic gear pumps the critical parts were the end plates. Think if there is wear in them the oil pressure holds them open from the gears instead of being behind the plates holding them tight to the gears. Might be a bit of oversimplification but that's what I recall.
This reminds me of a pump problem I had with an athey sweeper. Swash plate style hydrostatic pump dropped dead so we replaced it with a rebuilt pump and motor from fitzsimmons hydraulics. A week after the replacement the same symptom came up, loss of charge pressure. We removed the swash plate and some piece of trash went across the plate, so small you could barely grab it with a pick but it was enough to dump all of the charge pressure. Gotta have REALLY good eyes to find this stuff!!!
These aluminum body pumps are different in the pressure pushes the gears to the low pressure side as the bushings wear and the teeth start biting little bits out of the body. You can see the leakage is also happening at the end plates as well. New end plates have some kind of overlay which is gray in color. That is mostly worn off in the photos of the second pump. None of the seals on the back of the end plates showed any damage.