JD855 Tinkerer
New member
- Joined
- Oct 15, 2019
- Messages
- 2
- Tractor
- John Deere 855
I too had this issue and was more than confident it wasn't electrical. I've since got the PTO working again and thought others may benefit from an answer to this thread, albeit I can't vouch for whether or not the others had exactly the same issue that I did. I bought my 855 'not running' and the previous owner said it had been sitting for about five years. I've had it running, and all other hydraulic functions, including the loader, work as advertised.
Firstly, I confirmed that the mid/rear selection lever was doing something and that when not selected, the respective PTO was rotating freely by hand. I then disconnected the PTO engagement lever and actuated the engaging tab by hand to ensure that length of throw wasn't the issue, also 100% eliminating any chance of the issue being electrical. I was reasonably confident the inertia brake and clutch weren't receiving hydraulic pressure, so I aimed to start with the delay valve (items 1-12) that others have mentioned. To get at the valve, I wrestled the three way inlet fitting off the pump to buy me room, no need to drain hydraulic fluid. To remove the delay valve, I had to first remove the sensor below it (item 28) then remove split ring (item 1) and use a spare 6mm bolt to pull out the first part of the valve. Once the o-rings popped mine slid out reasonably easily, joined by lot of blackish hydraulic fluid and a little bit of metal swarf. The second half of the valve also takes a 6mm bolt to pull it out, and was much more difficult to get un-stuck.
Once on the bench I cleaned up the tiny little orifice in item 2 with a thin wire I pulled from the wire brush and lots of carb cleaner. Then I disassembled the second half of the valve, which is made up of a spring loaded plunger (items 9) on each end. Notably, one end was seized before disassembly. Disassembly was via removal of the two snap rings on either end, there was corrosion inside the bore of item 9 which I was able clean out with some light sand paper on my finger and a generous dose of spray lube. I hit the whole lot with carb cleaner to remove the metal shaving, then lubed it all up with hydraulic fluid before reassembly and confirming the plungers moved freely. I didn't have easy access to a Deere dealer for new o-rings, but they looked fine and I was keen to see if I was any closer to a functioning PTO. So valve back in, pump re-connnected and engagement linkage reconnected I gave it a whirl.
Almost instantly there was a response from the tractor that I hadn't been getting before. Over the course of a few seconds the tractor was bogging down harder and harder unto it would almost stall, but no PTO rotation before I had to cut the engagement to prevent stall. There was a little bit of smoke coming out the hydraulic breather each time I let the tractor bog right down, which I assume was clutch material. After a few goes, hoping that I was slowly forcing hydraulic fluid deeper into the inertia brake and clutch mechanism, I suddenly had success and the PTO jumped into life.
Confirming my success with a few more goes I suddenly started hearing strange sounds from the flow divider and filter, then lost all hydraulic power and instead had aggressive jerking. I've been putting off draining the hydraulic fluid since I bought and started rebuilding this tractor, but decided now as the time as I'd likely dislodged some 'stuff' into the filter or screen that was causing cavitation or a total blockage. Sure enough, when I pulled the plug there was almost no flow across the screen, which I then pulled. It was so full of 'stuff' that it had partially collapsed and now needs to be replaced entirely. Re-assuringly there doesn't seem to be any metal in the 'stuff' just grit and grime. I'm now waiting for a new filter screen, filter and fluid before I can fill it back up and check we're back in action.
Good luck for anyone else working on one of these tractors, I've certainly been enjoying working on mine and putting some life back into it.
