1978 John Deere 850 Project

[wct097]

Changed the hydraulic filter and topped up the fluid. Seems to be working a bit better. Don't have anything heavier than a bucket of dirt to lift, but it seems to work fine. The SCV is a little touchy and doesn't go back into a neutral position automatically. Easy to have the bucket curl circuit activated and not have as much power on the lift circuit.

Made a video of it running and all. Will upload it when I get a chance.

 

[CADplans]

This is a great vintage tractor,, I have a 650, and mowed grass with it today for 2 hours.
After looking at your pics,,, I WILL change the engine oil this evening when it cools off.

I got mine last summer,,,
since I do not know the history of the machine, I have been changing the oil every 25 hours.

So, did you stay within your $2K budget??

 

[wct097]

No, I'm over budget. I think I'm at about $2500 (not including the $1k purchase price) for the rebuild, new fuel injection pump, and a new seat. Still need soft lines on the loader. Might need an alternator.

 

[Fallon]

For normal operation, the knob between your legs should be fully counter clockwise. It regulates flow of oil into the rockshaft. The left scv lever should raise loader when pulled back and lower when pushed forward. There should be a detented position when pushed full forward to allow the loader to "float". the right scv lever should curl bucket back when pulling lever back and dump bucket when pushed forward.

Actually the knob between your legs controls the rate at which fluid leaves the 3pt cylinders, not the fill rate. If you screw the knob all the way in the 3pt won't drop at all. Unscrew it a bit & it will drop slowly. All the way out & it will drop fast.

At least that's how it works on every machine I've ever used.

 

[wct097]

Just a small update. The tractor seems to be running well. I replaced all of the soft hydraulic lines except those on the power steering. I've been using it on my property a good bit lately and getting the feel for what it can handle. Yesterday I need to move it and found that after it cranked up that the loader and the 3-point wouldn't lift. I had to let it run for several minutes to warm up before it would function. I didn't use it long enough to get really warm, so the function was extremely slow. Is that typical in cold weather with an old machine like this or do I have some other problem?

Followup question: Are there aftermarket hydraulic pump solutions that give a better flow rate? I've found that when warm and working that the loader is still pretty slow (compared to something like a Bobcat) and that the loader cannot function while the 3-point is lifting or the power steering is under load. I expect that flow rate is one issue, based on reading up on this tractor, but I figure I probably also have some other issues since the SCV is pretty sloppy and the loader sinks with the tractor off.

 

[Fallon]

Almost all tractors are open center. There is 1 loop of hydraulic flow going from valve to valve. When you manipulate a valve, it diverts flow from that loop to the impliment, starving everything downstream. So you can't run the loader & 3pt at the same time. That's a standard limitation of open center systems.

I bet your pump is worn, causing the slow performance. A rebuild or replacement would probably help. Measuring the flow rate of your current system would be a good idea to see how low your flow is compared to the OEM spec though.

 

[wct097]

Almost all tractors are open center. There is 1 loop of hydraulic flow going from valve to valve. When you manipulate a valve, it diverts flow from that loop to the impliment, starving everything downstream. So you can't run the loader & 3pt at the same time. That's a standard limitation of open center systems.

I bet your pump is worn, causing the slow performance. A rebuild or replacement would probably help. Measuring the flow rate of your current system would be a good idea to see how low your flow is compared to the OEM spec though.

Is measuring flow rate something I can do on my own with reasonably priced tools or is that something I would have to take my tractor to a shop for? If it were operating properly, would it still be likely to need to warm up before functioning when it's cold out (under 40*)?

The fluid leaked out when we had the engine off to rebuild. I changed the filter (external, under the right floorboard), and refilled with fresh fluid. Do you think I need to drain and refill the fluid again? Would this tractor have a screen in the sump in addition to an external oil filter?

 

[CADplans]

Is measuring flow rate something I can do on my own with reasonably priced tools or is that something I would have to take my tractor to a shop for?

With the tractor at operating speed,,, pump the hydraulic oil into a clean bucket for 5 seconds,,
multiply the measured amount by 12,,, that will be your flow per minute.

OH,,,, YEA,,, do not forget to dump the clean oil back into the tractor!! :laughing:

 

[wct097]

With the tractor at operating speed,,, pump the hydraulic oil into a clean bucket for 5 seconds,,
multiply the measured amount by 12,,, that will be your flow per minute.

OH,,,, YEA,,, do not forget to dump the clean oil back into the tractor!! :laughing:

Good stuff. I'll just have to figure out the logistics of where/how to pump that oil from.

I changed the filter and that seems to have improved the responsiveness. After the engine rebuild, it got a fresh filter and fluid, but while I thought it was drained/empty from the line being loose, I suppose there could have been some fluid left in the system. I think it would be a good idea to drain/refill the system again in concert with some of the fixes I know that I need to address.

This Fram filter is the one I changed. Does this tractor also have some sort of drain in the sump? Is that large bolt on the bottom the drain plug? IIRC, I tried to loosen that before and didn't have any luck.

My selective control valve is leaking fluid and the levers are sloppy. Neither lever returns to center and the lift lever seems to have overtravel when lifting where I can pull it too far and it stops lifting. I know this area needs work, but I'm uncertain as to what the fix actually entails. Would I typically be able to rebuild this or would I typically be replacing the entire unit? It appears to be leaking out of the top of the caps that the manual refers to as "float spool cap" and "lift spool cap".

Would most people typically replace this with a factory replacement or go for some sort of aftermarket solution? I assume the latter would require retrofitting and replacing hard lines with hoses to get everything to fit.

 

[jd110]

The plug you referred to is a drain plug. Try smacking it with a large hammer a couple of times before loosening, That usually helps to loosen it. Also there is a screen in that area of the sump. Remove the cap with 2 bolts on the left side to remove it and clean it. That may help your hydraulics significantly. Even if it looks clean, wash it in solvent, sometimes they get a slimy film on them that prevents good flow. The selective control valve may be able to be repaired. The return springs are under the spool caps and are secured with some tiny snap rings. Over the years, moisture gets in the caps and rusts the snap rings and they fail, then the valve is able to over extend and oil leaks past the O-rings. The worst part is the rust also deteriorates the snap ring grooves and a new snap ring sometimes will not hold. Some of the parts to repair the original valves are no longer available and complete valve may need replacement.