weak JD hydraulics

[JD805]

I bought a John Deere 790 in March 2008 and the hydraulics worked great. I just hit 120 hours and now the hydraulics seem weak, and they bleed off if they sit for a couple of days. I have hydrualic rippers on my gannon and even they bleed off. Ive heard of a couple people upgrading the pump but cant find anymore info. If anyone has any suggestions that would be great.

 

[J_J]

I bought a John Deere 790 in March 2008 and the hydraulics worked great. I just hit 120 hours and now the hydraulics seem weak, and they bleed off if they sit for a couple of days. I have hydraulic rippers on my gannon and even they bleed off. Ive heard of a couple people upgrading the pump but cant find anymore info. If anyone has any suggestions that would be great.

Those cylinders just might be weak , depends on use, wear and tear, etc. Pump could be weak due to same thing. If you are talking about cylinders leaking down, could be bad seals, could be worn spools in the valve, relief valve might not be set correctly.

You need to put a gage on the pump and see if the pressure is correct, and check the relief valve.

If you have to change out the pump, it might be rebuild-able, or install a new pump, and fix the rest of the system.

 

[J_J]

You mentioned upgrading a pump. Yes, you might be able to install a larger pump, but it will take more HP to drive it. If it will fit in the same space, and bolt up good, OK, but new pumps are not cheap.

 

[JD805]

Thanks, ill try it.

 

[kennyd]

Leaking down "in a couple days" is acceptable. There are lots of post's in the JD forum about raising the hydraulic pressure in the 790's, but I have never heard of changing the pump-I doubt you'd find on that bolts up.

Search the term "shimming" in the JD forum.