John Deere Mikanix

4640/4840 No Hydraulics, No Steering, No Brakes

There are some very simple items to check to verify the problem. First was the problem a gradual failure or an instantaneous failure. What that will tell you is whether something is wore out or if something broke. Second, plumb a gauge into the filter relief valve housing. You are checking to see if your Lube/Charge pump is putting anything out. If you see pressure move on to checking pressure at your main hydraulic pump. If pressure is going to the main hydraulic pump but nothing is coming out remove your system pressure relief valve and inspect it for sticking or wear. If the valve is fine plumb a flow meter directly onto the output of the pump to see if the pump is pumping anything. You could a have just a wore out pump. Now if you don't have any pressure at the charge pump pull out the plug on the filter housing a have someone hold a bucket at the hole and start the tractor if nothing comes out check the pickup screen before the pump is condemned. If the screen is clean as was the case on a tractor I recently did, then you have to tear into the rear of the tractor. The charge pump is located in the rear axle. You cannot just order a new pump. You have to order the specific pieces you need. In order to get to the pump you need to remove the rockshaft housing cover which is a lengthy process. The hole job including the making the special tools to lift the cover will take you between 20 and 25 hours to complete. In my case the pump was good but there was a huge hole in the outlet pipe of the pump.