Backhoe main hydraulic pump leakage.... EVEN AFTER REBUILD!

[muchtooffer48]

HELP HELP..... I have a JD500 series backhoe, I'm thinking about a 68-70 model, not really sure. It is a two stick, and I think it has two six volt batteries, not one twelve volt battery. Anyway, I bought this machine several years ago from the owner who had the pump rebuilt, and then sold it to me when the rebuilder refused to honor the warranty on the pump, and fix it right. This pumps leaks when the machine is running. I can not remember where I saw it leak but I'm guessing it is out the pump shaft, but I can't be sure. Maybe the builder of that pump didn't get the seals installed right, or damaged them when they were installed? Maybe these pumps have a history of this same problem that someone knows about. Can anyone direct me of the best way to go from here. Thank you very much. Frank. Hickory, n.c.

 

[jenkinsph]

I would test the system pressure to see what it is, according to tractordata it should be 2000psi. A 3020 would have been about the same at 2200 psi iirc. Just to get an idea of the pump condition regardless of what you were told. If it I leaking bad enough I would pull the pump and take it to another repair facility. If the pressure is excessive above 2500 psi I would slack off on the stroke control settings and see if that would help before removing the pump.

 

[muchtooffer48]

I would test the system pressure to see what it is, according to tractordata it should be 2000psi. A 3020 would have been about the same at 2200 psi iirc. Just to get an idea of the pump condition regardless of what you were told. If it I leaking bad enough I would pull the pump and take it to another repair facility. If the pressure is excessive above 2500 psi I would slack off on the stroke control settings and see if that would help before removing the pump.

Hey, this is just what I will do. So, could it be said that too much pressure could be causing leakage? If this is true, could there be a relief valve not working correctly? I guess I need to the book on this machine. That is the biggest pump I have ever seen. Someone told me somewhere that pump didn't pump anything until there was a demand. If this is true I may be in over my head. Thank you so much for your time. Frank. ps i hope i placed my reply in the right place.

 

[buickanddeere]

By design they all leak. It's a matter of how much . That drain line back to the transmission sump is there for a reason. It's a variable displacement closed center pump.The nice folks at 1-800-522-7448 have service and operator's manuals on CD and hard copy. The parts book is free online at the deere web site.

 

[jenkinsph]

This should be a variable volume piston pump once it builds the pressure to its highest setting it should go out of stroke. When a demand is placed on the system and fluid moves through a valve the pressure drops and the pistons start pumping again. The stroke control usually on the bottom of the pump is used to adjust this pressure setting. This would be typical for a closed center system.



If you had a gear pump with constant flow I would want o check the relief valve setting to see what you have. If a gear pump is worn enough fluid can easily get past the seals and a rebuild (complete) is needed. Open center system.

 

[Tx Jim]

If pump shaft has too much end play then this can cause pump shaft seal to leak. I disagree with b&d as I own a 4255 with nearly 11,000 hrs that the pump doesn't leak and hasn't been touched since it was new. I also own a 4440 with 10,000 hrs that hyd pump doesn't leak.

 

[muchtooffer48]

Thank you. I'll call and order a book tomorrow. Frank. ps thank you for the info. too.

 

[muchtooffer48]

Thank you for that info. I'm hoping I can check end play without removing the pump. I did that one time on an older fork lift we had. Those jd500 pumps cost several times what a 555 pump.

 

[buickanddeere]

Mother Deere put that drain line there for a reason. Everyone of those pumps weep some amount of oil past the seal.

 

[muchtooffer48]

Mother Deere put that drain line there for a reason. Everyone of those pumps weep some amount of oil past the seal.

Yes sir... I heard you loud-and-clear. I believe you. And I thank you for your time and your info.. I think I will start by ordering the book for this thing. I guess I first need to ID the year and s/n.

When, or if this DRAIN becomes stopped-up, if this drain could do so, how would I know? ( assuming the word, ''drain'' means, as in back to the tank with the leaking hydraulic oil. ) Would this be a closed pressure system or gravity system? Frank.