ZD21 lift deck works briefly when cold

[Mr. Lawrence]

Hello to all.

I'm new to forums in general....and I did search past forums before I started a new post....found some of the past links were dead.

I'm new to Kubota. I bought (from a dealer) a 2002 ZD21 with 1450 hours, but it has a deck lift issue. Seems it only works for a few minutes directly after startup.
Motor is a D782, it's clean, all original. Dealer had all the service records, seemed to be well taken care of. Both transmissions pull evenly, are strong, no noises, fluid is clean. Yet, the deck only works briefly when cold.

I pulled the lift cylinder and changed both seals. I installed a used (working) hydro lift deck unit off Ebay. I haven't changed the hydraulic oil and filter yet, but plan to do so sometime soon.

I let it run for several minutes before trying the deck lift, but there really wasn't any movement....by then it was already hot. I'll try again in the morning, but obviously it's still not working correctly. I'm not sure if there is a bleeding procedure.....my neighbor has several Kubotas and said the air will work itself out as it runs.....just let it idle awhile.

I did see in past forums, suggestions on cleaning or inspection the hydro strainers, or internal screen filters, but I didn't see any follow up if this resolved their issue.

I don't mind changing o-rings or seals...if I knew what i was looking for.
If anyone has resolved a similar issue, I would appreciate suggestions and link to some thing I missed in the past forums.

Respectfully,

Lawrence

 

[Bee-Positive]

Page 4-S1 of the WSM found HERE.

I would check the strainer first. Have you checked the pressure? Could be a bad relief valve.

 

[Russell King]

Try checking flow of the pump if you can disconnect some pipe or hose on the pump discharge. Don’t let it run long or you can pump the sump dry.

If you want you would be better off checking the pressure in that system instead of flow (but you might not have a gauge).

 

[Mr. Lawrence]

Page 4-S1 of the WSM found HERE.

I would check the strainer first. Have you checked the pressure? Could be a bad relief valve.


View attachment 177960

Thank you for the quick reply. The manual was a nice touch.
I'll pull the strainers when I change the hydraulic oil.

 

[Mr. Lawrence]

Try checking flow of the pump if you can disconnect some pipe or hose on the pump discharge. Don’t let it run long or you can pump the sump dry.

If you want you would be better off checking the pressure in that system instead of flow (but you might not have a gauge).

Thank you for the quick reply. I'm not sure how to do this yet....I have a service manual....and member Bee-Positive just sent me a more detailed manual.

This is my first commercial mower, and diesel engine... I'm still figuring things out.....what things are and where. I think I have a cylinder compression gauge...somewhere... Maybe I could put it on the end of the hard line to the deck lift hydro unit. I'm guessing that is what you mean by the pump discharge pipe.

I'm guessing I'll find the pressure specs in the manuals somewhere.

 

[Russell King]

See post #31 in this thread for the type of pressure gauge that you need. The gauge needs a 3000 PSI upper range. The one in that post is mounted to a manifold for easy connection into a system but you can just use fittings and hydraulic hose.

M5700-loss of power steering after running awhile

Are you operating it with the three point in a full up position? Go to the tractor and start it, raise the rpms to where you normally work with it. Lower the three point wait a min, then raise the three point to the top, does the hydraulic noise change, and do the rpm's drop slightly? If so then...

www.orangetractortalks.com

But don’t test hydraulic systems unless you have some idea of what you are doing. The hydraulic fluid is under enough pressure that it is dangerous and can cause it to be injected through your skin and cause a lot of medical problems.

 

[Mr. Lawrence]

See post #31 in this thread for the type of pressure gauge that you need. The gauge needs a 3000 PSI upper range. The one in that post is mounted to a manifold for easy connection into a system but you can just use fittings and hydraulic hose.

M5700-loss of power steering after running awhile

Are you operating it with the three point in a full up position? Go to the tractor and start it, raise the rpms to where you normally work with it. Lower the three point wait a min, then raise the three point to the top, does the hydraulic noise change, and do the rpm's drop slightly? If so then...

www.orangetractortalks.com

But don’t test hydraulic systems unless you have some idea of what you are doing. The hydraulic fluid is under enough pressure that it is dangerous and can cause it to be injected through your skin and cause a lot of medical problems.

I know just enough about hydraulics to be very cautious. I may be able to check with the farms around me to find a make-shift gauge already in use.

 

[Mr. Lawrence]

Looking through the manual and now understanding a little more...I believe the issue would be with the pressure to the deck lift hydro. Since I have already changed the old unit out, and rebuilt the lift cylinder with no change.

i'll see if I can locate a high pressure gauge first, go from there if i can find one. Strainers would be next during my oil change. I'm pretty sure the last owner used UDT2, same as what I bought. I'm not sure how old it is, but it looks clean.

 

[Bee-Positive]

Page 4-S3 shows how to check the relief valve.
Page G-45 has gage and adaptor information. Not sure if you need all the adaptors, I've never done a ZD21.

 

[Mr. Lawrence]

Me either. I did print out pages 197-200 that covers the inspection. I did replace the original deck lift hydro (whole unit) with an ebay replacement.....that didn't fix the issue. I would hope both the original and the Ebay replacement wouldn't both have an issue with the relief valve, but it's possible.

Hopefully cleaning the strainer(s) and adding new super UDT2 will fix the issue. I might wait until the end of the cutting season to do the oil service. Shouldn't be another cut or two considering my deck is stuck at 2 1/2". I'll have the deck off for spindle replacement and a gear box rebuild before I have any issues from that unit.