Hydro-Gear PJ-12 pump

[bigsnowdog]

I am going to disassemble a Hydro-Gear PJ-12 pump because it is leaking from the output shaft seal. It also seems to have some radial play in it that the other pump does not display. The machine, a Ferris 3100, has 122 hours on it. Unfortunately, I am out of warranty.

The right side motor circuit stopped working unexpectedly while mowing. Interestingly, the left side motor circuit seemed to still work. I saw the reservoir was about half full. I picked the machine up with my loader tractor and took it to my shop. There I discovered a lot of surfaces were wet with oil. Further inspection seemed to suggest it was the right side motor.

I have gotten seal kits from the dealer and have downloaded a .pdf from Hydro-Gear on the motor.

I am wondering if any of you have first hand experience working with these motors. I have a good mechanical background, having worked as an automobile and truck mechanic, and did disassemble a garden tractor's hydrostatic transmission once years ago out of curiosity. But, realistically, I have no experience working on these.

I am interested in any helpful hints you may have before I begin this task. The dealer said that sometimes the bearing gets loose and causes the seal to leak. The right side pump has perceptible motion and the left side does not. Apparently Hydro-Gear's approach to parts is they want you to buy a shaft with bearings. The dealer said to just get them at a bearing house and put them on the old shaft.

Are there any holes I am about to step in here? I am thinking I should go ahead and do the other motor now also, since it is a fair amount of time and effort to get this far into it. The other motor is, of course, the same age, so it may go next.

Thoughts?

A first question; what is the disk at the top of the shaft? Does that require a puller?

 

[Carl_NH]

BigSnow.

Sorry I dont have experience in these pumps BUT, I have a Ferris IS2000 with the same 12CC pumps and like you have a decent understanding of hydros and pumps as I worked on many Cub Cadets and IH hydro tractors in my time.

As to the top fan mount hub - you can likely separate the bottom half without pulling that off exposing the bottom side and innards of the pump - two gear type motors I presume.

I will be following this with interest because my !S2000 has 60 hrs now, is out of warranty end of next month and my hydro oil is not clean (brown) and has a sort of burnt/used smell to it that I dont like.

I just ordered two 51563 hydro filters from Hydrogear on line and intend to change my oil and filter out as soon as they arrive.

The manual says 250 hrs before a change but what the hour meter registers on the Ferris is cutting hours ( when the deck is engaged) and mine was leftover that made many trips back and forth to the showroom without cutting a thing..

Anyway, keep in touch and let me know how you make out - BTW I agree with getting a bearing from the supply house and doing the seals.

I will stay tuned to see how you make out.

Thanks again,

Carl

 

[bigsnowdog]

I got the heavy washer-like part off the shaft using a battery terminal puller, of all things. It worked fine.

Once you get that small top cover off [which I punch-marked to indicate orientation], you will see a small spring and ball. Note their location and pull them out of their bore. I got the notion of orientation from a video on Youtube about rebuilding a different model Hydro-Gear pump. The video indicated a primary reason for improper operation was that top cover reversed from where it belongs.

Turning the pump over I removed a snap ring. The shaft is supposed to pull out the bottom. The seal is holding it in. I used a dead blow hammer to tap it out the bottom. A spring remained behind inside. For the moment, I believe it simply slides on the shaft. There is notable end play in the assembled pump. Given this reality regarding shaft removal, I conclude the end play is normal?

The bad news is that the bearing on the lower end of the shaft is bad. The cage is broken up in pieces, many of which were lying on top of the seal. That is why the shaft orbited and why it leaked fluid.

There may be more reasons, like a piece of cage is stuck in valve somewhere.

The symptoms again; I lost the right side function and the left side was not real good. The reservoir is about half full. Now I am wondering if the lack of function results from debris migrating somewhere in the system and either blocking a passage or interfering with a spring loaded check valve or other valve.

It makes me wonder how to flush this out. It also makes me think I should do the left side motor also. Bearing and seals.

The kits from Hydro-Gear seem to have too many parts. There are a lot of parts. Multiple model applications, perhaps?

I believe I will buy the bearings, as Hydro-Gear only services them as a bearing and shaft assembly. Why?

I would rather not disassemble the wheel motors to check for debris. Any experienced thought on that?

 

[Carl_NH]

BigSnow,

You have made good progress- thanks for the update, also, each side serves each motor so I would blow air both ways thru the lines to the right side motor. If you can get new oil into the line (sticking the one line in oil while pressurizing the other with air) should suck oil in as its a motor driven by pressure. Maybe use some lighter weight mineral oil then 15-40 synthetic.

On the left side since its more or less independent (after the filter) it should not be contaminated but I would disconnect the motor lines and flush, then do the same in the pump.

From here, I would put a magnet on the filter and run it (Wheels up/off) with the bypass all the way open and cycle the handles back an forth. Opening the bypass circulates the oil to the tank and back and not the motors.

On the bearings I agree, get them locally.

I apologize about my lack of specific knowledge on Hydrogear but hydraulics are pretty much the same and anytime this occurs your need to clean out as best possible which I think you know too.

Keep us apprised to your progress.,

Carl

 

[Carl_NH]

BigSnow,

I went out and did a detailed look over the plumbing setup on my IS2000 (by the way my pumps are labeled 070223 vs yours) when did you put yours in service? I can see the return lines come from the motors to the central tank and is recirculated/split back to the motor so there is a constant loop on the pump/motor with a portion to the recirc tank which is filtered. This should keep the bad stuff on the right side pump/motor and not impact the left side,

The concern you have is where did the pieces go? You could have pieces stuck in the inputs to the right side motor - if they went thru the motors I can imagine a replacement motor in the future.

As deep as you are try the air/oil flush as I suggested earlier both ways to flush any particles from the motors, or just remove the lines and check for debris.

Also cut the old filter apart (first) and see what you find - also the bottom of the resivoir tank for filings.

Most of the guys on Lawnsite forum replace the units ($450 ea for a pump and $400 for a motor) so $1600 for all 4 - the most $$ components after the engine IMO.

Keep us informed on your progress,

Carl

 

[bigsnowdog]

I picked up two new bearings today. One for the bad pump and one for the other pump. In talking with the dealer, he told me he had never seen a wheel motor damaged by debris, so I will hope for that.

I paid serious money to buy this new. I can't rationalize or accept buying expensive, new parts when the machine only has 122 hours.

 

[bigsnowdog]

Lessons learned.

It is possible to remove a snap ring and remove the seal from below. You have to have a way to hook the seal to pull it. If the bearing is fine, then that would be the way to go. The risk is in how you hook or pierce the seal to pull it. I did not have what I considered to be a viable answer there.

if you pull the shaft, or drive it out, to remove the seal, then you leave a spring and washer behind inside the housing. You cannot put that back on the shaft and slide it back in with the shaft. You have to remove the end cap and cylinder block assembly.

The cylinder block assembly looks somewhat like the cylinder from a revolver. There are seven pistons in this pump. When you pull the cylinder block out you will likely have pistons and springs come out of the cylinder block.

In behind, or below, the cylinder block there is a thrust bearing and race that rides in the swash plate. It is possible the swash plate will fall out once you have removed the cylinder block assembly. There is a small, square piece called a slot guide. It will probably fall off or out, too.

Hydro Gear has a great .pdf of a service manual available. It is long, covers many models, and initially is a bit off-putting, but it has a lot of good information and illustrations.

Assembly necessitates putting the shaft and bearing in the empty housing first, then retaining it with the seal and snap ring. There is a spacer between the seal and the bearing.

The seal seems a slip fit in the bore. I would expect it would have to be driven in, but..... apparently not. It is not clear to me why that does not leak, or at least weep.

I think [I have yet to do this] the hardest part will be to get the cylinder block back in the housing. You are supposed to lay the housing on its side. That is great because that orientation will keep the pistons from falling out of the cylinder block. The downside is that I am not sure how likely it will be for the swash plate to fall from its position.

Petroleum jelly is mentioned as an assembly lubricant for O-rings. I wonder if it would also be acceptable for retaining little parts.
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[Carl_NH]

With respect to pet jelly I would use mobil 1 15-40 synthetic during replacement of the pistons and swash plate and the same for seals just to make them a bit more pliable and prevent tearing.

Also a piece of plastic (saran wrap, or thin plastic) wrapped around shaft or threads you have to slide over minimizes chance of tearing.

Thank you for the well written update. Did the pistons or swash plate have any scoring?

Last I wanted to mention I changed my hydro fluid yesterday - removed the filter and drained the tank. I was surprised how dark the oil was - not as black as diesel oil, but it was dark as used motor oil.

I didnt drain the lines or wheel motors (60 hours on machine) but refilled with 1 3/4 quarts of Mobil 1 15-50 - I think the total system holds two quarts roughly? I then ran for about an hour and checked the temp -180F after running - shouldnt be burning the oil at that temp..

Thanks for the update and let me know how you make out on getting up and running again,

Carl

 

[bigsnowdog]

There was no scoring. Barely any even on the end cap.

Regarding the saran wrap, I was assembling the pump, watching the top seal approach its journal. I don't think there is enough of a risk/corner to need that. It is a good thing to observe, however. You would want to make sure you did not get any little bit of it torn free and left between a seal lip and its journal, however, so you did not get a leak from it.

Interesting about the temperature. I admit, I would not know what to guess as an expected temperature. That is pretty hot, isn't it?

I will keep you posted!

 

[bigsnowdog]

Some photos of the work. The first is the empty housing. The second is the swash plate, thrust bearing and race. The third is the cylinder block assembly with one piston and spring removed.