After replacing hydraulic pump seal & o-rings hitch not raising correctly - JD 850

[Smedium C]

After replacing hydraulic pump seal & o-rings hitch not raising correctly - JD 850

After replacing the seal and the 6 o-rings in the hydraulic pump the 3-point hitch will only raise about 1/4 way under load. Raises all the way up if nothing is attached. The pump is the 9cc model.

After replacing everything I noticed the hydraulic pump shaft was a bit tighter when spinning it by hand but the seals were in bad shape and assumed this is how it should be with fresh seals.

The lift worked just fine before I opened the pump I just had a nasty leak. Nothing has been altered on the tractor other than the pump.

Anyone have an idea of where the error might have occurred or something I'm overlooking? Any help would be greatly appreciated. This is a John Deere 850 older model but seeing as the only JD thing about it is the green I figured this forum would probably be the right place to post.

Thanks

 

[winston1]

Re: After replacing hydraulic pump seal & o-rings hitch not raising correctly - JD 85

Have you cracked a line assuring you are even getting much flow. Possibly not primed? Just something to ponder.

 

[majorwager]

Re: After replacing hydraulic pump seal & o-rings hitch not raising correctly - JD 85

What about the lift cylinder itself. Pressure/flow worthless if cylinder has failed.

 

[rScotty]

Re: After replacing hydraulic pump seal & o-rings hitch not raising correctly - JD 85

I assume you bled the lines and confirmed that you have flow everywhere. I haven't done any 3pt work on Yanmars, but I do have access to some shop manuals.
What is happening when it quits lifting? Does it sound like the engine is laboring? Will it lift a full load, but only partway? It sounds like it won't lift weight.
Yes, I agree that the JD850 is a Yanmar in all but color.
Does it have the cleanable hydraulic filter down at the bottom of the transmission case in addition to the spin-on filter like the other Yanmars? That cleanable filter is notorious for needed to be cleaned.
rScotty

 

[Smedium C]

Re: After replacing hydraulic pump seal & o-rings hitch not raising correctly - JD 85

I just pulled the inlet line off and there was fluid in the pump. I added a little more just in case and tried again. No luck.

I'm not sure how to check for flow throughout the system and following the manual I have requires the purchase of a few tools/gauges which I may have to do.

Everything worked fine before replacing the seals, other than the leak, so I don't see why the lift cylinder would be out.

As for bleeding the lines, the manual doesn't state a process or recommend doing it in the hydraulic pump section. From what I've read, working the lift lever back and forth should cycle the oil and let any air escape in the reservoir. Also, the fluid was changed and screen cleaned about a month ago. I would say it's definitely something to do with what I've just done.

After priming the pump and attempting to work the lever again I noticed the pump got pretty hot in just a minute or two. It was still doing the same thing. It will only lift the shredder a couple inches from the ground. There may have been a slight noise coming from the pump area but I'm not familiar enough to say for sure. When I had the shredder off the lift would raise 100%.

I'm wondering if either there's a slight error in how I reassembled (everything looked correct and only difference I noticed is that once I tightened on the back plate the coupling became quite a bit tougher to turn - but still turned each direction fine), or I didn't properly seat the pump when mounting (very difficult spot to see into so I arranged the coupler as it was when I pulled it and it seemed to slide right in after a wiggle or two).

Thank y'all for helping out. If I need to come up with some equipment for further diagnosis I'll see if I can borrow or purchase if necessary.

 

[winston1]

Re: After replacing hydraulic pump seal & o-rings hitch not raising correctly - JD 85

Another thought or two. Possible left the shaft key out on the pump coupling? Possibly left keys out on pump gears?

 

[Smedium C]

Re: After replacing hydraulic pump seal & o-rings hitch not raising correctly - JD 85

#4 was in place when reinstalled. I never saw #7 or a place where another would go. The diagram is pretty ambiguous with that shaft key and not sure what to make of it.

 

[kenmac]

Re: After replacing hydraulic pump seal & o-rings hitch not raising correctly - JD 85

well, worked fine before you took everything apart. I'm going to assume (something I don't like to do) that you have installed something in the pump incorrectly.
You shouldn't have to bleed anything as this is an open system.
You should be able to check flow by removing the fill cap and look inside to see fluid flowing.
Not an indication of how much flow , but you should see if circulating

 

[winston1]

Re: After replacing hydraulic pump seal & o-rings hitch not raising correctly - JD 85

Pretty mysterious. At this point I would pull the pump, set it in a container with fluid, turn with drill or something and assure what is going on. The heat build up you earlier spoke of indicates a problem, either lack of fluid, something broke or binding. Evidently something in the pump is turning or it would not get hot.

I do notice on the John Deere sight there is also an 11cc pump available but assuming that is not what you have as your drawing is showing the 9cc pump.

 

[Smedium C]

Re: After replacing hydraulic pump seal & o-rings hitch not raising correctly - JD 85

I pulled the pump off yesterday and tore it apart again. It all looks just fine to me. Again, the only thing I find strange is that once I put that back plate on that presses against 4 new o-rings it gets a heck of a lot harder to spin by hand. I'll try spinning it in some fluid as it's still on my table.

Is there any possibility that I have some flow restriction somewhere but since the o-rings were worn to **** and it was spinning so easily that it was compensating for the blockage but now can't?

Yes, it's the 9cc pump.