2016 Bobcat S510 RH Drive Issue

[skeleton]

Looks like this forum has some great info, so much that I signed up to get some help with my S510, any input would be appreciated.

Info on machine:

Got a new to me 2016 Bobcat S510 with ~1000 hrs. Supposedly already serviced.
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Problem:

I started to have intermittent trouble with the RH side drive, where it wouldn't want to move with either a load or say when in a ditch or where there was more force required to move the wheels. This issue eventually got worse and triggered an error code for low charge pressure.I stopped using the machine and ordered a new charge filter and parts to do the 1000hr service.
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Troubleshooting performed:

I did the 1000hr service. I found that the charge filter was plugged with debris (I cut it open). There looked to be some sort of sludge with a slight amount of metal particles, very small. When changing the main hydraulic filter, I found that the plastic bottom of the filter had broken off of the filter itself, and was sitting in the bottom of the filter housing.

I changed the tank oil and ran the machine up. Changed the filters again and found small particles in both filters, which looked to be more sludge type debris, not really any metal.

I then disconnected the top hose going from the RH pump half to the top of the motor (reverse), capped it at the motor and connected a gauge on the hose. Ran it up with the parking brake applied, when trying to move (reverse) I hit 6000 psi on the gauge and kept climbing.

Next, I disconnected the bottom hose going from the RH pump half to the bottom of the motor (forward), capped it at the motor and connected a gauge on the hose. Ran it up with the parking brake applied, when trying to move (forward) I could only hit 3800 psi.
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My thoughts:

At first I had thought the pump was failing internally, possibly due to residual debris stuck in the system after a component failure and not flushing everything out.

After looking at the filters, even though they were caked with debris, there wasn't much metal in them, just tiny specs, and not many of them. This is making me think that the debris found in the filters is actually remains of pieces of the bottom of the main hydraulic filter that broke off. Cooked plastic, or some other contamination? Perhaps the rotating group of my pump is good, just flooded with plastic debris, and my relief valves are not operating properly due to the debris being stuck in them.
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My Questions:

1) My engine is the Bobcat D24NAP, has anyone pulled the tandem drive pump out without removing the engine? It looks to me like if I get a short enough puller, say the OTC 6614, I can get the pulley off the pump with everything in-place, then pull the pump out.

2) I have to take a look at the pump again, but I'm thinking that I can pull just the RH half of the pump out, while leaving the LH half in place? Any reason not to do this other than the LH half already being contaminated and needing cleaning?

3) Anyone have any better tech data than the bobcat manual for rebuilding the pump? Judging by the logo on the pump housing, it looks to be a Sauer or Sundstrand. Its Bobcat PN is: 6687863​

 

[skeleton]

Got the pump out. I left the engine in place and used the OTC 6614, but had to cut the forcing screw down to ~4" to fit between the pulley and the frame. Since I wanted to clean the oil cooler, tank, filter housing and fan motor, I opted to pull the pump straight up and out through where the fan and oil cooler reside.

I'm about to tear down the pump, can anyone educate me on how Danfoss pumps are identified? I have the bobcat manual which includes the disassembly and reassembly, but I imagine Danfoss might have some tech data that's a bit more in-depth. Also, anyone have any advice about these pumps as far as anything that I should pay particular attention to?

 

[skeleton]

I disassembled the RH half of the pump, or at least part of it.

Judging by the amount of corrosion on the interior of the pump pieces, water got inside at some point then was never discovered or addressed. I still do not have a definitive conclusion as to the source of the contamination of my hydraulic system, but I would bet that at some point in this machine's life it, or at least part of it was submerged under water. Either plastic from a broken main hydraulic filter is the cause of my contamination/sludge, or while under water dirt and debris entered the reservoir.

Who know's, and does not matter now.

Aside from the corrosion, it appears that the broken spring on the FWD relief valve is the cause of my inability to build pressure.

 

[skeleton]

Rest of pictures:

 

[zlssefi]

great pictures. sorry i did not see this sooner. my gut tells me you are correct. broken relief spring would certainly cause this issue! nice job!

 

[skeleton]

In an effort the clean out the contamination from my system, I disassembled the gear pump, and cooling fan motor. The gear pump was clean. The cooling fan motor was caked with debris.

The reservoir had and still has a bunch of sludge caked all over the bottom of it. I was able to dislodge some of the debris, which looks to be the same stuff that I originally found lodged in the charge filter when I first started troubleshooting this issue. At first glance I thought it was metal of some sort, but crumbles under your finger when pressed. I'm thinking a mixture of cooked oil and plastic. I'm thinking a new reservoir is in my future.

I still haven't addressed the oil cooler, anyone have any great ideas on flushing it out?

 

[skeleton]

rest of the pictures:

 

[Clint485]

Did you end up getting the machine back together? I have a 07 s330 that has a similar problem but I didn't find a broken spring like yours not letting it build pressure. I haven't been able to get a code fault from it.

 

[skeleton]

Not yet, I'm waiting on parts to show up and my oil cooler to return from getting flushed.

I'll upload some more pictures later, took one motor apart and geroller looks good, but I had one broken spring on the shuttle valve. Springs on shuttle valve and poppet were rusted pretty well.

The combination of broken relief valve spring and the amount of contamination was my problem. It's not back together yet, but my pump still built pressure, just not in one direction.

 

[melben]

I have refaced many of the scarred up brass shoes with a piece of flat glass and 400 grit emery paper, using a light oil I do a figure 8 motion, stop, grab the shoe another location, repeat till the scoring is gone. I have saved commutator plates as well and you can redress up the end of the rotor face where it mates with the commutator plate. I have many like new with a minimum of expense. It takes a little time but the price of that stuff adds up quickly.

Your first clue would have been the good pressure in one direction and low in the other, the rotating group works the same for either direction and the high pressure reliefs control each side separately, a bad charge check valve could also let high pressure away but failure of them is rare.

 

[skeleton]

Good idea for cleaning up those shoes. Since time is in short supply for me, I opted for a reman pump.

I removed and cleaned just about every hose connected to the pieces I was working on, got my oil cooler flushed and cleaned up, got a new oil reservoir due to the amount of debris lodged in the old one, disassembled each drive motor and replaced all seals and o-rings and springs, the geroller sections of each were still in good shape. I primed the system, ran it until the oil reached temp., drained the reservoir and changed the filters. I ran it up again, drained and changed filters. Seems to run like it should now, which is good as I don't really feel like taking the pump out again.

Interestingly, the bobcat brand charge filter has no bypass. The Baldwin filter I was using does have a bypass.

This is the charge filter when I first noticed and started diagnosing the problem, pretty scary.

 

[skeleton]

Here is the element from the charge filter after my first flush:

Much better looking.

 

[skeleton]

The motors:

 

[skeleton]

I forgot to bring this thread to a close, so here it is for posterity sake:

I got a reman pump installed. There was no need to remove the engine, I was able the get the pulley off the pump by shortening the forcing screw of my puller.

The machine worked great with the new pump, for a while, then the RH motor started slowing down. I replaced the RH motor with a new unit from Bobcat and all is well.

After I got everything fixed up and running smoothly, I started thinking. I goggled the serial number of my machine, and after quite a bit of digging, I found an auction result listing for my machine. The listing noted that the machine had drive issues once up to temp. The seller was a bank. Well I now know where the guy that I bought it from got it. Lessons learned, do a better inspection, and don't buy used stuff on ebay even if the seller in FL has a 100% feedback rating.

Cheers!