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manant

hydrostattic pump and motor assembly

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manant    9

I have a 1977 c160 auto that stopped working after mowing for a while.  The lift had been getting sluggish, but one day when I stopped for fuel I did not come to a complete stop before engaging the brake.  When I started up again I had no hydraulics - no forward, reverse, or lift.  With help from this forum I removed the pump and motor and inspected the check valves and push valve.  They looked OK to me - none seemed stuck open or closed.  I could not get the acceleration valves taken apart but used penetrating oil to see if they were working and they seemed to be.  The forward and reverse check valves were very difficult to remove but I finally got them out. I also noticed that there was no shim on the implement valve plug, but the lift had been working for years with no problem.

 

I then opened the pump housing and inspected the cylinder and sliders, and they seemed OK.  The sliders did not have deep scratches but were darkened a little.  I removed each piston and gently polished the sliders with Brasso on a hard smooth surface. The Gerotor looked OK to me.  When I reassembled the pump the finned housing would not go all the way to the end plate unless I pushed it in hard to get the bolts started.  I now assume I was compressing the spring in the cylinder.  Once together the shaft was hard to turn by hand unless I put the pulley on.

 

I did the same with the motor, except I did not remove the cylinder.  I just removed the pistons one by one and polished them as I did with the pump.  I reassembled the motor, connected the pump and mounted on the c160.  After filling with oil I started up and no forward or reverse.  I had slight forward rotation but with no power at all and no reverse.

 

Upon reflection I do not remember applying pressure to the motor housing to connect the bolts like I did with the pump. Could my problem be with the spring in the motor piston assembly?  After reading the repair manual I do not remember anything about compressing the housing with the bolts.

 

In any regard I am a frustrated camper right now, and realize that I have to remove the pump and motor and start again.

 

I am also curious about the torque values for the various check valve plugs and connectors between the pump housing and plate, between the pump and motor, and mounting to the gear box.

 

Any thoughts or suggestions would be appreciated.

 

 

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pfrederi    2,906
Posted (edited)

Sorry for your pain...it isn't fun.  Does your hydro lift function?  Does the engine labor when you try to move forward or backwards?

 

If you have to pull it again just be thankful it isn't a D series...

I am not awareof any torque specs...also several us have struggled to get the valve caps removed they can be super tight.

Edited by pfrederi
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manant    9

Thanks for the quick reply.

The engine does not labor at all.

I do not have anything on the lift right now and the cylinder is fully extended.  It is difficult to push the cylinder rod into the cylinder with nothing on the lift.  I do have a minor leak in a hose connection on the lift control valve.  After turning the engine off, I made the mistake of taking the high pressure hose off of the cylinder and shot oil all over the place when the hose popped loose, so it looks looks I have pressure at the cylinder.

I have not found anyone who lends or rents a high pressure gauge to check the pressure.

The local TORO dealer does not work on the Wheel Horse any more - he says the parts are hard to find.

 

I still wonder it the motor piston spring is the problem.

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pfrederi    2,906

From a quick read on reassembly of the motor it should push back me.  Page 45 item 11.

 

Did you press the piston block off past the spring clip...most the ones I tried I broke the spring clip and had to get new ones.:(

 

The hydro pump should be able to turn with your bare hands but it should take some effort.

 

I have a pressure gauge set up.  PM me your address and I will send it down to you   I am not planning on tearing into any hydros in the near future..

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Are you sure your drive belt is fully engaged? You said it broke when putting on the parking brake, right? Have you checked all your linkages to ensure they are all functioning? Maybe it's stuck in parking mode.

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manant    9

I read the section you mentioned but could not tell that  I had to compress the piston spring.  The first line of your note was not complete so I am not sure what you were saying.

I did not take the piston off of the shaft.  I did not know how it was held on, but now know about the spring clip. I probably have to take it off the shaft to check the spring and spring clip.

I can turn the pump shaft by hand but it is tight. Easier to move with the pulley on.

I may have found a local guy to work on the hydro system and will check on Tuesday. I would rather do it myself if I can just for the satisfaction.

 

pfrederi what branch of the Army?  I was in the Corps of Engineers.

 

To FATJACK, I did not break the belt.  The belt and pulley are working.  What I said was that something broke when I engaged the brake.  It was a mild crunching sound. All linkages are ok.

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pfrederi    2,906
Posted (edited)

The way I read it you had to push the cover on and tighten down the bolts to leave 3/16" gap before the next step.  it has been awhile since I took my last one apart but i thought there was resistance pushing it on.  Perhaps the sudden stop did damage/break the spring inside of the piston block.

 

The reason I asked about laboring the engine was to make sure part of the parking brake hadn't locked up the transaxle if it jammed it the engine would labor. You should be OK there.

 

You can do it yourself, don't let it get to you...

 

Medical Service Corps

Edited by pfrederi
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manant    9

Paul, I received the gages today and very much appreciate your sending them. 

Unfortunately, I have almost no charge pressure - at most only about 15psi.  If I put it in forward or reverse it drops to 5 -10 psi.

I tried the implement gage as well but figured that if I had no charge pressure I would have no implement pressure.  I had no reading on the 1000psi gage.

Back to square one.  I will take the pump and motor off and go from there.  Any suggestions?

I can return the gages immediately or hold on to them for the next step - whichever you prefer.

Again I appreciate you help.

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pfrederi    2,906

Hold on to the gauges.  First step is make sure the charge pump and implement relief valves are functioning correctly.  Make sure the springs are in place, not broken and the right one is in for each valve (Light Charge heavy implement) and that they are on the correct side (charge on the left implement on the right as you look at the end of the pump unit.)  I believe you can do that with out removing the hydro unit...again be thankful you are not working on a D series.

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manant    9

I am sure the valves and springs are correct.  I did get the plugs mixed up but caught the error before I made the assembly.  I do not think there was a shim on the implement plug, but I think that would just make the Implement psi higher. I will look closer to see if it is in the bore when I take out the plug.

My drive belt is old, but that should not have caused an immediate stop in the hydraulics when I applied the brake.  I put a new belt on but it was one from O'Reilly Auto and not Toro. It was the proper width and length although it does look a little loose when the drive pulley is not engaged.

I next plan to put the old belt back on and try the pressure test again.  If still no pressure I will check the charge and implement valves again.

You are right that I can take most of the valves out without removing the hydro unit.  The only ones I can not get to are the acceleration valves.

Thanks again.

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953 nut    14,230
3 hours ago, manant said:

only ones I can not get to are the acceleration valves.

We will cross that bridge when and if we get to it. If forward and reverse control was strong and smooth before they are probably not a problem.

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pfrederi    2,906

To have that little charge pump pressure would to me mean one of two things  A;  The charge pump is in terrible shape (I think you would have seen that when you had it a part  or B:  Something is letting the charge pressure bleed off too fast  (Summarized bin teh captures...

 

Good Luck!!!!

 

pressure.JPG

pressure 2.JPG

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Oldman    17

Say, I found a section the manual about the internal plug , referred to as "b" in the diagram page 50.  That's my two cents? I just had the exact same failure on on a "D". I am still working on her this day! I had a second pump, still going back together though.

 

Internal.png

Internal plug.docx

Edited by Oldman

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manant    9

I saw the p.50 diagram with the loose plug note.  I think that diagram is for an earlier pump ( pre 1973).  My pump (1977) does not have the external plug on the side of the end cap.

 

The more I think about it, I think/hope the problem is in the spring load on the motor cylinder.  As I have said I do not remember any force needed to assemble the motor housing as I found with the pump housing.

Regardless, I have put the old belt back on and plan to pressure check again today.  If no pressure I will remove the hydro system again and check the motor cylinder.

 

Thanks for the help.

And thank you all for your service to the country. I have seen Army, Marines, and Navy respondents so far.

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manant    9

I ran it with the old belt and no change - 10psi.

 

I have removed the unit and started taking it apart.  I still have not gotten the motor cylinder off.  I want to read that section again about using a hammer.  I know it might break the retaining clip.

I will get back to it on Tuesday.

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pfrederi    2,906

Even using a press as suggested I broke the clip.

 

LJ Fluid power has them

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manant    9

Here is the latest.

I did not know where to find a press to remove the motor cylinder.  After some thought I remembered the screw jack on my cider press and used it to remove the cylinder. When it came loose it really popped.

 

I got the motor piston assembly off and there were metal bits in with the cylinder spring.  The clip was broken, perhaps by me when taking it off. I do not know if the metal bits are from the broken clip.

The spring and Spiroloc retaining ring look OK. However the retainer itself was also damaged, maybe when I broke the clip.  I also saw a broken needle from one of the bearings - probably broken by me in the process. The big problem may be the valve plate has deep scratches - can feel with fingernail.

The Implement valve, Charge valve, push valve, forward and reverse valves, and acceleration valves appear to be OK.

 

I also dismantled the pump to look at its spring and cylinder. They look OK, but that pump valve plate is also scratched - not as bad but still able to feel with fingernail.

So far it looks like I need:

 1. Motor valve plate No 69 on the diagram

 2. Retainer No.73 on the diagram

 3. Retainer clip No 74 on the diagram

 4. Pump valve plate No 24 on the diagram

 5. New needle bearing No.84 on the diagram

 

I am sure I can get the needle bearing locally but am lost on where to get the other parts.  If you can salvage them from one of your parts units I will be happy to pay you for them.

 

I am still puzzled why the hydro unit stopped suddenly.  I understand the gradual loss of power or pressure as the valve plates wear or become scratched, but the system stopped as soon as I applied the brake.

Any help would be appreciated.

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pfrederi    2,906

Does your unit have a brake band (Physical Brake) on the end of the hydro motor shaft??  Mine are all to old to have that feature.  I wonder if it is possible to apply that brake while the pump was still pushing fluid into the hydro motor.  Maybe the counter force broke something???

 

I would try resurfacing the valve plates.  Fine wet sandpaper on a sheet of glass  I started with 400 and worked up to 1200 the some crocus cloth to finish.  (any in my parts units would have to be resurfaced)

 

I will check later to day to see if I do have #73 and 74

 

If you want to go new contact LJ Fluid power.  The are nice people but be prepared for sticker shock.  A couple years ago he had pump valve plates but didn't have motor ones.  Apparently the standard Sundstrand motor plate has to have some machining done to it to work on WH hydro motors???

lj.JPG

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manant    9

Thanks.

My brake is a simple toothed cog in the gear box.  The external lever rotates the cog into place.  I too thought the sudden stop could have broken something ( thought perhaps the motor cylinder spring, but the spring looks OK) In fact I have not seen any broken items other than those encountered yesterday and probably caused by me in removing the retainer clip.

 

I had wonderd about "polishing" out the scratches on the valve plates.  I do not know how much bronze one can take off and still get the compression needed.  Regardless, that will be my next step before checking on new replacements. I did some minor polishing of the pump valve plate with 1000 grit emery cloth on a hard level surface and finishing with Brasso on a cloth on the same surface.  I will do the same again and also work on the motor valve plate which is in worse shape with scratches.

 

I think I can take a Dremel tool to the retainer (No 73) and clean up the burrs that the clip gouged out.  That part should have a fair amount of tolerance since it just hold the clip in place. I will  remove the burrs and polish the gouges.

I will definitely need a new clip and will contact the local TORO dealer or L J Fluid Power if you do not have one.

Thanks again

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Did you check your woodruff keys between shaft & gear? Or a twisted shaft? From what I understand of your description, I would also check the gear train.

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manant    9

I have not taken the gear box apart but looked in and saw that the gears all turn as they should and the brake cog engages the gears when the lever is actuated.  I think my problems are in the hydraulic pump and motor.

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