hydrostattic pump and motor assembly

["Manic-Mechanic" 1,195]

There is a post here in this section, that explains the whole rebuild process, very well done post too. The post does state to make sure not to run the pump dry be sure to have oil in this pump.

 

[manant 57]

I read the section on hydro rebuilding and am happy to say my unit was not in as bad a shape as the one shown.  Mine is clean inside.

I also read about the mating of the gerotor gears.  I did not see any reference to that in the hydro manual. I also did not make note of the specific orentation of the gear sets. I know I removed the inner gear to check for scratches and may not have put it back in the proper location.  It seemed to rotate properly.  How do you figure out where they should mesh, or are they unsalvageable now?

[manant 57]

I mounted the hydro unit and the pressure gage only showed about 25psi at full throttle and belt engaged.  The implement gage did not show any pressure.  I do have forward and reverse motion on the wheels.

I had previously removed all seven of the check/push/acceleration valves and inspected them and they looked OK.  I guess one of the valve seats could be damaged and not letting the ball seat properly. The other guess is that I have not worked on the slippers and pump valve plate enough to get them completely scratch free.  I thought they looked pretty good. The pump and motor do not make and loud or grinding sounds, in fact they are relatively quiet and seem smooth running.

 

 I am still puzzled as to why all hydraulic pressure was lost instantly.  I know my lift pressure was dropping as the unit heated up, but I still had lots of forward and reverse power until I engaged the brake.

I have noticed that the brake lever arm that the drive pulley engages is worn, but I can press down on the drive pulley to apply more belt pressure and I see no difference in the gage pressure.

 

Back to square one and frustrated.

 

[pfrederi 17,887]

When you put the motor back together did it resist the last 1/2 inch or so??? (springs inside the piston block)

[manant 57]

Yes.

I used a bolt and washers as the instructions said to remove and examine the spyroloc ring, washer, spring, and retainer. The spring was OK and I got rid of some burrs on the retainer.  Everything went back together OK.  I assembled the motor as the guide said.  Tightened to about 3/8 inch, then put on the snap ring, o-ring and end cap, and then tightened the bolts the rest of the way.  I did have to press down on the housing to compress the spring as I tightened the bolts.

[pfrederi 17,887]

I am stumped.  The sudden failure when braking would I thought indicate something snapped or broke like the springs in the piston blocks or the keyway in the input pulley.

["Manic-Mechanic" 1,195]

Really interested in seeing what the issue is? I have yet to remove the hydro motor on this machine. Even though it's a divorced system perhaps something similar is going on?

[manant 57]

I do not think my pulley has a keyway.  The shaft has splines as does the pulley. The pulley definitely turns the pump shaft.

There may be a broken key in the gearbox, but that should not affect the hydro pressure.

I do have a minor leak in the lift control where the hose hooks on.  Oil does not spurt out but it does drip.  That should not affect the pump pressure very much.

Both the motor and pump pistons had to be compressed to assemble the units, and the springs looked OK when I had it apart.

[pfrederi 17,887]

Grasping at straws a bit here.  When you did the implement pressure test with the cylinder at full extension you got no reading at all (or just not enough to register on the 1000 psi gauge)  Try it with the 300 psi gauge do you get the same reading ad the basic charge pump test?

[manant 57]

I did not try the implement test with the 300psi gage, only with the 1000psi gage. I think it was just not enough to register on the 1000psi gage

I have been using the side port to hook up the gages.  It should not matter, but I think I will try hooking up to the port on top of the pump end cap.  If I only get a 25psi charge pressure there, I will try the implement test with the 300 psi gage.

 

Since I do have some minimal pressure and wheel rotation, I am thinking about putting everything back together and just try riding around some to see if something loosens up.

 

Have you received my mail package, and if so what did you thing about the pump valve plate?

[pfrederi 17,887]

50 minutes ago, manant said:

I did not try the implement test with the 300psi gage, only with the 1000psi gage. I think it was just not enough to register on the 1000psi gage

I have been using the side port to hook up the gages.  It should not matter, but I think I will try hooking up to the port on top of the pump end cap.  If I only get a 25psi charge pressure there, I will try the implement test with the 300 psi gage.

 

Since I do have some minimal pressure and wheel rotation, I am thinking about putting everything back together and just try riding around some to see if something loosens up.

 

Have you received my mail package, and if so what did you thing about the pump valve plate?

 

 

Sorry yes i got teh package.  That 2 tiny scratches in the plate wouldn't cause that big a drop in pressure.  It wouldn't be like new but I doubt you would notice anything.  My D200 ran decently with much worse plates..just got hot.

[manant 57]

I went by the local John Deere dealer seeking help and a man gave me a lead to call a precision hydraulic shop about 65 miles away. I did so and was able to speak to a man who knows about Sundstrands.  He said the slippers and valve plate specs are for flatness to be about 5 millionths of an inch. Since the lift had slowly lost power as the oil heated up he suspected that re-lapping the slippers and valve plates might fix the problem.  My polishing by hand "probably" did not meet specs. Since the pieces are a lot smaller than what they normally work on he said it might cost me $40-50 for them to lap both motor and pump piston assemblies and valve plates. 

I am now going up to the shed to drain the oil, remove and disassemble the hydro unit and package them to take to them on Tuesday.

Hope it works.

[pfrederi 17,887]

Could you take a picture of your slippers and valave plates before yu take them in...and after??? Would like to see how much difference professional work makes.

 

Good Luck

 

I am still stumped on why the sudden failure....

[manant 57]

Today I took the motor and pump cylinders and valve plates to a hydro shop. The guy at the hydro shop put my valve plates on an optic flat machine and showed me how out of flat they were.  He said if they are not perfectly flat the piston cylinder would “wobble” enough to lose charge pressure.

He is going to lap the bottom of the cylinder. the valve plates, and the piston slippers. He also called the company you mentioned and ordered an new retainer ($20) and a new retainer clip ($20) plus the internal washer and spirolock ring.  Looks like I am about up to $100 in parts and service.

[meadowfield 2,595]

tried to read through, I'm a little late to the party, isn't the charge pump a gear pump on this unit?  there aren't really any plates to wear or polish are they?  Assuming the main drive is a piston pump and that would explain why you are discussing grooves in the valve plate.

 

If you have no charge pressure then it can either be the pump isn't turning, the relief valve is broken or the oil is leaking from the charge pump cavity.

 

I have a diagram to show the oil flow on a sundstrand piston piston unit

 

Edited August 30, 2017 by meadowfield

[manant 57]

I really do not know much about these.  The gerotor pump is inside the pump cavity and feeds the pump cylinder/piston assembly. Those pistons, cylinder, and valve plate were scratched which I assume causes a loss of pressure.  The same with the motor, both pistons and valve plates were scratched releasing oil into the motor housing and back to the gearbox sump.

I also thought that the problem might be a loose ball valve.  I took them all out and they look undamaged, although the valve seats may be the problem.  I do not know how to check the seats.

The gerotor pump does turn.

Thanks for the input,

[manant 57]

Here is the latest news.

When I removed the motor shaft again I broke the new retainer ring, the spiroloc ring and the washer.   What I did not realize until yesterday is that when I pressed out the ring the shaft also pushed in too far and ruined my new needle bearing.  In removing the damaged bearing I also ruined the other bearing and seal.  I have ordered two new bearings and seal.  My hydro shop had already ordered a new retainer clip and retainer,

spiroloc ring and washer.  He will finish lapping the slippers and valve plates and reassemble the motor cylinder for me.  Will get them next week.

 

While I am waiting I plan to replace the needle bearing in my pto housing.  Anyone know how to get the old one out?  I found a thread on this site but the photos do not show up because of photobucket. I think the ball bearing is OK but the needle bearing is missing one needle.

 

I also want a c160 right hand tie rod. Mine had the ball slip out.  I pinged around it to keep it in but I am sure that is only a temporary fix.

Thanks for all the help.

Marshall

[BOB ELLISON 2,981]

WHEELHORSEMAN PARTS and more

In the vendor section has the ball joints.

I've ordered from him and they are the same replacement for the C160's. 

 

[manant 57]

Here are the photos of the refinished valve plates and slippers.

The guy at the hydro shop said that the motor valve plate was warped and that alone could have caused me to lose charge pressure.  The parts were also scratched badly.

You can see that the refinished parts are completely free of scratches.

 

I also learned that

 1. The pistons are completely interchangeable  even between the motor and pump cylinders.  You do not have to put them back in the original holes.  I know the argument about the wear patterns etc, but to lap the pistons he removed them and put them into a special cylinder for the operation.

 

2.  You do need to fill both the pump housing cavity and the motor housing cavity with oil before running the transmission. Both piston cylinders are supposed to be completely bathed in oil. I assume the filling will be a tedious task since the only way to do it is through the top ports like where the test gage is mounted.

 

3. The Gerotor teeth do not have to be in any particular recess in the outer pump ring.  The outer ring has one more slot than the Gerotor has teeth and as the Gerotor turns each tooth switches to the next recess so that each tooth enters all of the recesses in the outer ring. So it does not matter where it starts.

 

I will complete the transmission assembly on Saturday and mount it to run the pressure test.  Wish me luck!