Bobcat 331 - Slew not holding, bucket not overpowering thumb, foam in reservoir

My Bobby was acting odd today...while holding a log on a slight incline, the machine wanted to slew very slowly downhill while in idle. Normally, it holds position. Also noticed bucket curl couldn't overpower thumb...
Lastly, noticed a little bit of foam in sight glass...it was hot, and while letting machine cool down, the foam dissipated.
Bad section in pump? Relief valve?
I keep the oil fresh, albeit I went with a no name big store bucket of 46.

All of these problems might be related to an air leak sound I had a couple of weeks ago through reservoir cap. I cleaned the cap...didn't appear to be the problem.

melli said:

My Bobby was acting odd today...while holding a log on a slight incline, the machine wanted to slew very slowly downhill while in idle. Normally, it holds position. Also noticed bucket curl couldn't overpower thumb...
Lastly, noticed a little bit of foam in sight glass...it was hot, and while letting machine cool down, the foam dissipated.
Bad section in pump? Relief valve?
I keep the oil fresh, albeit I went with a no name big store bucket of 46.

All of these problems might be related to an air leak sound I had a couple of weeks ago through reservoir cap. I cleaned the cap...didn't appear to be the problem.

Click to expand...

Nobody got nothing?
Well, after pouring over schematics, I figured I ought to try looking at build up valve on manifold. A - It is the easiest thing I can pull out and B - it actually might be the problem. It might be dirty/stuck open, and it is connected between pump and swing motor (sits on manifold).
Apparently, it keeps the line charged at 150psi. If stuck open, it would allow fluid to backtrack to pump...and when at idle, the house was creeping downhill. Not sure if it would contribute to foaming in the tank....
Not sure what is happening with thumb (aux) overpowering bucket...could just be a port relief valve not doing it's thing...
Just odd everything happened at once....they must be connected.

Actually made up a test kit to check pressures at ports on manifold, but it appears I have the wrong quick connect...rectify that tomorrow I hope.

I was butting in on another thread about my home made pressure kit. Got it up and running...

Got all the pressures (FYI - using different hydraulic functions uses different stages of pump - I have a 3 stage pump P1, P2, P3)... Everything is within specs, albeit on low side, except Main Relief on Manifold block (P2 & P3) - 3300psi (range 3400-3550)). Was hard to get swing over relief as I couldn't get lock on swing to engage, so I used blade as a stop, and arm was fully over relief. Looks like I can adjust main relief to get some more oompf. P1 was 2600psi (boom offset at full relief gets me that number). (range 2550-2700psi) Swing motor (P3) gave me 2650psi going both ways (2650-2950 range). So, generally, all looks good...other than Main Relief has some room to play with. Looking forward to actually adjusting that, as it may give me more oompf on swing and arm. To tuckered to pull out tools and adjust right now...will update once I adjust. Really glad it appears I have no major issues.

I am wondering if the ISO 46 oil I got (no-name) is causing some issues. Once I get some good oil in there, and adjust the main relief, I bet I'll have some more bite.

GSP2 Box 14R uchida hydraulic pump

Seems I have a Uchida pump...no idea if it is OEM or not. Was hoping a Bobcat pro could tell me if there are any bulletins on the main pump (GSP2 Box 14R Uchida hydraulic pump - made in Japan) and if there is a cross reference to another pump, in case I need to get another one, one day. Seems Rexroth and Uchida are merged?

Finding information on the main pump is like a black hole...like what ISO oil it likes, for instance.

The reason I ask is I'm about to adjust the main relief on manifold block and it would be nice to know what the specs on pump are...
If I am digesting this hydro maze right, if one adjusts the main relief valve, it brings up all pressures on P2 and P3 section of pump. Consequently, any functions using those pump sections will increase also?

I am 150psi shy of target psi on main relief...it is the only value I measured that is shy of specs.

BTW - the diagnostic tester I made is fairly cheap (less than $200 all in). I changed a couple of things from pic shown...I hardwired line into T, and used the quick disconnect for the 1000psi gauge, so I can disconnect it when testing the higher psi's. Plus, I have the proper diagnostic female coupling (not shown).

Uchida builds pumps using Rexroth designs under license, it's a common arrangement for Japanese manufacturers. Not all Uchida pumps are Rexroth compatible though.

I think that pump number is just for the gear section? The older 331's had a three section gear pump I think, the newer ones are a combination piston with a gear pilot/third section? Should be a model AP2D18 I think. Pictures of the pump?

lantraxco said:

Uchida builds pumps using Rexroth designs under license, it's a common arrangement for Japanese manufacturers. Not all Uchida pumps are Rexroth compatible though.

I think that pump number is just for the gear section? The older 331's had a three section gear pump I think, the newer ones are a combination piston with a gear pilot/third section? Should be a model AP2D18 I think. Pictures of the pump?

Click to expand...

Yep, your right...thanks! (number for gear section only - three section pump).

Can't make out number on other two sections as it is covered by gear section, and backside is covered in crud...need to wash it off to see if there are numbers there....

I've never seen a pump with a grease zerk in the side of it before, gotta wonder if that's original......

There should be a tag riveted on the piston section somewhere out of view.

lantraxco said:

I've never seen a pump with a grease zerk in the side of it before, gotta wonder if that's original......

There should be a tag riveted on the piston section somewhere out of view.

Click to expand...

That is just to bleed air after draining reservoir and refilling.
Yeah, I'll clean up backside and see if I can see something.

Haven't gotten around to cleaning backside of pump yet...not in a cleaning mood...lol
But I did adjust the main relief valve on the manifold! My first play with hydraulics. I don't count the myriad of hoses I've replaced or ram tinkering as hydraulic work.
I'll admit, I was a bit daunted by all the hoses and valves everywhere...slowly, I am starting to understand how it all works.
Was cool being able to adjust pressure...and it was ridiculously easy. Might even move Bobby into a new weight class....lol
Ok, maybe not...
On mine, the main relief is just behind the main diagnostic port. Loosen locknut, and use an allen key clockwise to increase MR pressure. One full turn equals 500psi, so I didn't have to turn it much to get back in the zone (bumped it up 100-150psi).
The result was the bucket now overpowers the thumb (back to normal), as it should. It didn't before, and that was my first clue something was wrong.

no name fluid can spell disaster for hydraulic systems if it doesnt meet spec..I only use fluid that meets or exceeds manufacture specs , I try to use either new holland or John Deere fluids...

Yeah, my manual states that 10w-30 engine oil (assume 2003 best oil of that day) was fine for my system.
I don't have all the bells and whistles newer machines have...
Once I can get specs on pump, that will tell me which ISO oil it likes....

Finally cleaned off backside of pump to see tag:
Uchida - Rexroth
EC023S9666-2
Model AP2D12LV1RS7-966-2

If anyone has specs, manual, whatever...sure appreciate it.
I have no idea what it is...I'm guessing AP stands for axial pump...after that...no idea.

Great posts Melli, this is the kinda stuff I need. Every tidbit of info helps.
I long for a thumb on my TB-016 but first I want to fab up a coupler to get rid of the Waine/Roy setup.
I fussed around looking for oil a few years back & found a local industrial supplier with the correct ISO in clear,seems everything else is amber colored.
Now their gone & had to get some amber colored juice @ the Auto-Zone.
My slew never did hold so it's either a tension adj. or more likely worn linings.Dare I hope to find the hydraulic relief setting wrong? Nah,not on a former rental unit.
Thanks again
Jay

AirBorneOne - `I long for a thumb on my TB-016 but first I want to fab up a coupler to get rid of the Waine/Roy setup.`
You have a fixed thumb?
You'd be surprised what a little adjustment to main relief can do, if that is the problem. Everything seems to be back to normal on mine. Slew seems to be holding while idling. After playing with diagnostic rig I made, I think everybody should have one in their tool box. Kinda guessing if you don't...lol
My thought was crossport relief valves (can't adjust those - two on swing motor) were on their way out, but with diagnostic gauges, I could see that pressures were good there...
The only pressure out of spec was the main relief on manifold. That's the beauty...you can pretty much check EVERYTHING with gauges through diagnostic ports.
Even check pilot pressures (joysticks). Surmised all three sections of pump were good (by checking all controls). Although, I don't have a setup to check flow rate on pump sections....that setup is expensive. Nonetheless, I feel I can peer into the internals, and know what to play with, if something goes wrong. Before, I had no clue.
I broke down and bought Bobby oil...I still have some left, so I plan to do a viscosity test on Bobcat/10w-30/ISO 42. My feeling is ISO 42 is too heavy. Won't be a full on lab test, but it doesn't really need to be...just see how fast a unit flows/time. As long as they are all at same temps, it will tell me what I should be using in lieu of bobcat oil. Not against Bobcat oil, it's just I live an expensive shipping distance away, nevermind the cost of it.
Have to give props to the Bobcat manual...they give you a chart, and with gauge in hand and a pen, you just move each control to full relief pressure, and jot down the number on chart. Once your done, you know where the problem is....best.
Suggest getting a diagnostic hose long enough to reach into cab from diagnostic port.

I was yapping with a pro on another board, and was wondering why these machines don't come with a diagnostic panel...like driving a car with no gauges. I suppose it would add to the cost, but my setup was $150...

Melli,
I have no thumb at all.
Decided to convert from Wayne/Roy coupling ($1,000.00 quote for tool side 'box' !!! ) before adding a thumb.
I'm a simple homeowner/operator so no rush to change.I pin on an auger setup when I need a posthole.
Definitely need to setup a hydraulic test gauge kit.
I suspect my rental unit was 'de-tuned',I would like to at least check.
Maybe Bob specs 10w-30 to allow for operation @ working temps.?
J

Well, the story I've been hearing, is older manuals, including mine, state:
If Bobcat fluid is not available, use engine oil
SAE 10W-30 or 10W-40, Class SE or better.
However, newer manuals do not give this as an option. I guess too many folks were taking the non-Bobcat option, depriving Bobcat of extra cash.

There is nothing in manual that states if one uses 10w-30 or 10w-40 to ease up on operation temps.
I've just been trying to find a manual for my pump....that will likely tell me the oil specs required. The pump is the key. Cannot even find manufacturer specs on pump, nevermind parts. Ironic, manual even has instructions how to do a complete rebuild. I called my Bobcat dealer to order a part for it, but they had nothing...

Although, my manual does have pump flow control specs, etc., I don't have the money to buy a flow control test kit. That would be handy, but the pressure kit I have indirectly measures the pump's health.

melli said:

Finally cleaned off backside of pump to see tag:
Uchida - Rexroth
EC023S9666-2
Model AP2D12LV1RS7-966-2

If anyone has specs, manual, whatever...sure appreciate it.
I have no idea what it is...I'm guessing AP stands for axial pump...after that...no idea.

View attachment 160166

Click to expand...

HEy melli, what year machine do you have. I just blew a hydro pump and The pump they sent me is the same pump you have but mine is a 966-1. the suction port is bigger than mine and my port block wont work. so im looking to find the right port block from bobcat.