I don't know the JD system but most use hyd pump for lifting and let gravity lower it. For that to work you need a electric hyd bleed valve to operate and release the fluid pressure to lower. If the orfice in that valve gets clogged or doesn't operate properly you get the problem you are seeing.

I highly doubt you need a pump, but JD may not sell the hyd release valve separately if it is in the pump/motor assembly.

 

Thank for the response. You definitely seem to be at least partially correct, maybe fully correct. After reading your post I googled Mowers For Dummies (as in I did a little more research). It turns out the button on the right handlebar is not to lower the deck- it is instead only to shut off the PTO, so it works as it should. The left handlebar raises the deck (just fine). The deck doesn't stay up when I let go of the button, but if your gravity suggestion is correct, than it should not stay up. I now think that the dealer was trying to sell me $1,500 in parts I don't need. Sure, the deck does not "easily" lower via gravity, however, I can try lubing things up, and worst case I have to put a little pressure on the deck when I want to lower it, and I save $1500. As long as it goes up and I can lock it with my dial, I should be fine.

 

Pump outlet pressure is generally put through a check valve to hold pressure in the lift cylinder. Internal leakage can occur in worn lifting cylinders causing a slow creep downward. If the check valve becomes held open by debris or the ball doesn't seat correctly, this will also cause the creep downward. Most check ball assemblies are removable for service or replacement.

My dump trailer has such a system, pump on, for lift through a check valve. Lowering uses an electric pressure dump valve to return fluid trapped in the extended cylinder and returns it to the tank.

 

It seems like the John Deere "convenience package", which has this hydraulic deck lift option. It does not have a button to lower the deck though, only raise it. Does that sound right? Should there be a button to lower the deck? Or do you just let go of the button that raises it and wait for the deck to gradually lower back down on it's own?

 

Maybe get the manual for it?

 

I did take a look at the manual. It only references the button to raise the deck. It does not mention anything about lowering, whether it should lower on it's own, how quick it should lower, if the button should lower, etc. Manual isn't helpful, unfortunately.

 

My Z997R Diesel is waiting to be put together otherwise I would know more. Let me read the manual both mowers should be similar.

 

The deck defaults down, the button is to lift the deck, it resets down if the button on the handle is held for more than 20 seconds. check your height adjustment is not dialed up to max as this is the transport position.

 

Thanks for the response. So if you hold it for 20 seconds it will default to down. What if you simply hold it for the 3-4 seconds it takes to raise it, and then let go of the button? Should it go back down on its own?

 

Try releasing in some of the spring pressure on the deck assist, two long Springs run under the mower bottom of the back tires should be four and a half inch I believe, that will help gravity bring the deck down. Back out quarter inch at a time equally on both sides until it floats down by itself.