JD 920 hyd system question

[selkie]

Looking at a cheap used (... very used!) JD 920 diesel. Seller says engine, clutch, transmission are good. He's been chasing hydraulic problems on it for awhile, with a lot of very fine metallic junk in the filter. He had thought it was the pump, changed it out for a pump he'd gotten at Grainger (they sell generic pumps for these?), didn't fix it. Took the loader off, didn't fix it. He said that cleaning the junk out of the filter gets him another year out of the tractor each time, which for him is something like 10 hours of use.

He's asking 1800 with the loader. That's kinda my price range given my work situation (... = plenty of time on the homestead). I'm OK with putting work into it, but I don't want to buy a junker. Does this sound like it's too far gone? Or worth a closer look?

 

[beenthere]

What I read, hydraulic fluid contamination from metal can be difficult to filter out and a continuing problem with all parts that are in contact with that fluid and rely on it being clean.. bearings, gears, valves, etc. Same hydraulic oil is moving through the transmission as well...

At least, run down a place to send samples for an analysis.

And what is happening that is evidence that it isn't fixed yet after replacing pump, removing loader, etc. ? i.e. what stops working?

Might be better places to spend your $1800.

 

[selkie]

What I read, hydraulic fluid contamination from metal can be difficult to filter out and a continuing problem with all parts that are in contact with that fluid and rely on it being clean.. bearings, gears, valves, etc. Same hydraulic oil is moving through the transmission as well...

Oi. So in other words, the system is likely going to just eat itself?

And what is happening that is evidence that it isn't fixed yet after replacing pump, removing loader, etc. ? i.e. what stops working?

The filter clogs again with more junk, apparently. It sounds like the seller stopped using the 3ph because that wouldn't work either once it clogged.

Might be better places to spend your $1800.

In fairness, the seller was wondering if it would be better as a parts donor. He didn't sound like a bad guy, just like someone who was sick of fighting with the thing.

I'm used to old questionable machines and don't have the budget for very recent stuff, but I don't want something that's going to be a money pit or fall apart when I need it.

 

[Tx Jim]

My guess is brake linings have deteriorated and brake parts are metal to metal. I'll bet hyd oil is milky indicating moisture which causes brake pads to fail. That model tractor has open center hyd's which are a little easier to diagnose/repair than JD closed center systems. $1800 is cheap enough if loader frame is good. I suggest to R&R both rear axles to check/R&R brake pads. I also recommend installing bovine magnets in bottom of trans case where hyd oil screen is located.

 

[rScotty]

My guess is brake linings have deteriorated and brake parts are metal to metal. I'll bet hyd oil is milky indicating moisture which causes brake pads to fail. That model tractor has open center hyd's which are a little easier to diagnose/repair than JD closed center systems. $1800 is cheap enough if loader frame is good. I suggest to R&R both rear axles to check/R&R brake pads. I also recommend installing bovine magnets in bottom of trans case where hyd oil screen is located.

It sounds like the owner hasn't ever gotten down and cleaned out the system and put any real effort into finding the problem.
If the hydraulic fluid looks like milk instead of being clear that is water contamination and half the problem right there.
The fact it still works when cleaned out is HUGE! As is a good engine and tranny. Yes, it could certainly be nothing more than the wet brakes and water in the oil.... it is something like that. If you get it, be sure to get the old JD pump as well as the new Grainger one.

If you are a guy who enjoys being a mechanical guy, that is a whole lot of tractor for a guy with $1800 - but I'd offer 1200....
You can recover that by selling off the loader if it comes to that. But that tractor with a loader and working right would be a jewel.

If you decide to get it, us TBN guys are going to want you to clean out that hydraulic system properly while figuring out where the problem is.
When I didn't have money but plenty of time for cleaning, I'd have jumped at it. It all depends on whether you are willing to work on it every evening for a month flushing it really well. For me there was a time not long ago when it would be worth the gamble. Especially with a loader on it that can bail you out for $1000 most any day.
And even more so if the engine and tranny really are good.

Will it lift the 3pt hitch with an implement on it and hold it up while you drive it home? If so, offer less and then get it.
rScotty

 

[selkie]

My guess is brake linings have deteriorated and brake parts are metal to metal. I'll bet hyd oil is milky indicating moisture which causes brake pads to fail.

Tried to check with the seller today to confirm that he hasn't tried that yet - I do remember him saying something about asking a dealer to look into the brakes and being told they didn't think that was it. But he did describe the fluid in some funky way and the tractor definitely lives outside.

I suggest to R&R both rear axles to check/R&R brake pads. I also recommend installing bovine magnets in bottom of trans case where hyd oil screen is located.

Hey, speaking of that, where do I find a service manual if I pick this up? Looks like they're kinda scarce on fleabay.

If you get it, be sure to get the old JD pump as well as the new Grainger one.

I'd asked the seller about that. He said he might still have it, was going to look. Rebuild kits available?

When I didn't have money but plenty of time for cleaning, I'd have jumped at it.

That's me right now...

Will it lift the 3pt hitch with an implement on it and hold it up while you drive it home? If so, offer less and then get it.
rScotty

Hmm, good test. I'll see what he says about whether it's likely to do that. I haven't cleaned one of these hydraulic filters out before, is it something I can just bring tools and do? Or more involved than that and not meant to be a routine service item?

 

[rScotty]

I guess the owner doesn't have an operator's manual. The op manual shows how to adjust the brakes for wear - and doing that will tell you if they are worn clear down. Seems an odd thing to have a dealer check. Funky probably means milky - which means water in the trans/hydraulic fluid.

It is common for water to get into the system when a tractor is outside without a tarp on it. A simple tarp is the answer to half the tractor problems we see. Without it, water can drain down the shift levers into the transmission sump which is also the hydraulic sump. The transmission and hydraulics use the same oil and hold the extra in the transmission sump. Hence: trans/hydraulic oil.

You can use a lightweight cheap high detergent motor oil to do your trans/hydaulic flushing. Some even use diesel fuel initially for a quick flush, followed by running with cheap high detergent motor oil as the trans/hydraulic fluid for a few hours, then drain and follow by a good transhydraulic fluid after all the crud is flushed out.

It can - and will - take several flushes and maybe a few filter cleanings/changes before you get to put good transhydraulic oil in there and leave it. Each tractor has a different filter system, but they are always on the suction side of the system. It is common to have at least two filters. One is often a cleanable filter (which may be internal or a screen under an access plate on the side of the transmission) AND an external spin-on replaceable filter that looks like a spin-on engine oil filter. But spin-on for the hydraulics is typically heavier metal and the darn things cost 4 times as much as an engine oil filter.

There are rebuild kits for some pumps, not all. Still, there is a lot to be learned about the tractor from studying any failed part, and unless the pump is really badly damaged I'd rather have an OEM JD part to rebuild than someone elses replacement.

Whether you get it in printed or digital form: You want an operator's manual, a parts manual, and eventually a service manual. I'd start with the first two. It's the operator's manual that you really want to find in printed form. Digital is good enough for the parts manual and is also available on the JD website. You want the tractor operator's manuals because the ones from JD typically contain all the maintenance operations that you need to know at this point. The Service Manual is more for doing overhauls. You wouldn't be using the Service Manual at this point. What you are needing is the get the maintenance right.

If the hydraulic system will lift the FEL bucket and the 3pt implement and keep them there long enough to drive a few miles home - even if you have to keep lifting them as you go - then you probably have enough good left in the hydraulic system to be able to fix it up once you get to your shop.

It's not optimal, but I strongly doubt you are going to find much better for that price. But get ready for a month of greasy evenings getting the maintenance going in the right direction. If you aren't into that, don't bother to get started. And even so, you may run into a problem that means scrapping the project for what you can get out of the FEL. So be honest with yourself about your time.

If helps to accept that a tractor doesn't have to be perfect but just better than it was. All of the older JDs are good candidates for what you want to do. This one probably isn't the only one you will find.
luck,
rScotty

 

[beenthere]

Can look up parts at the jdparts for the 920.
https://partscatalog.deere.com/jdrc/navigation/equipment/58556

Schematic of the screen location and what the hyd oil filter look like..
Note two different filter covers key #8 and #10 depending apparently on s/n

 

[Tx Jim]

I guess the owner doesn't have an operator's manual. The op manual shows how to adjust the brakes for wear - and doing that will tell you if they are worn clear down. Seems an odd thing to have a dealer check. Funky probably means milky - which means water in the trans/hydraulic fluid.
rScotty

The only adjustment for the wet brakes on a JD tractor of that era is adjusting operator pedal height if height is incorrect & bleeding air out of braking system if air is present. No other adjustments were available. Any tech manual designed for a 20 through 40 series JD utility tractor with open center hyd system should be fine. I have a tech manual for a 2040 that covers the open center hyd system. I just sold a Koyker loader that would fit that tractor for $2000,

 

[selkie]

I guess the owner doesn't have an operator's manual. The op manual shows how to adjust the brakes for wear - and doing that will tell you if they are worn clear down. Seems an odd thing to have a dealer check. Funky probably means milky - which means water in the trans/hydraulic fluid.

Yeah, I don't get what's up with changing the hyd pump yourself and then taking it to the dealer for a brake adjustment.

It is common for water to get into the system when a tractor is outside without a tarp on it. A simple tarp is the answer to half the tractor problems we see. Without it, water can drain down the shift levers into the transmission sump which is also the hydraulic sump. The transmission and hydraulics use the same oil and hold the extra in the transmission sump. Hence: trans/hydraulic oil.

Pretty sure there wasn't a tarp on it, and given the tractor's general condition I'm sure whatever protected the area around the shift levers from water isn't doing much protecting anymore.

You can use a lightweight cheap high detergent motor oil to do your trans/hydaulic flushing. Some even use diesel fuel initially for a quick flush, followed by running with cheap high detergent motor oil as the trans/hydraulic fluid for a few hours, then drain and follow by a good transhydraulic fluid after all the crud is flushed out.

Oh, that's good to know. We bought a bunch of that stuff (cheap motor oil, not diesel) awhile back when it was marked way down. I didn't use it in the cars, so it's just sat.

Also have gallons of surplus 75w90 gear oil that I'd bought for a song way back when, but I'm guessing that's way too heavy for this.

There are rebuild kits for some pumps, not all. Still, there is a lot to be learned about the tractor from studying any failed part, and unless the pump is really badly damaged I'd rather have an OEM JD part to rebuild than someone elses replacement.

Sure, and now that I think about it, if replacing the JD part didn't fix the problem, then the JD part was probably still good.

Whether you get it in printed or digital form: You want an operator's manual, a parts manual, and eventually a service manual. I'd start with the first two. It's the operator's manual that you really want to find in printed form. Digital is good enough for the parts manual and is also available on the JD website. You want the tractor operator's manuals because the ones from JD typically contain all the maintenance operations that you need to know at this point. The Service Manual is more for doing overhauls. You wouldn't be using the Service Manual at this point. What you are needing is the get the maintenance right.

Ah ok, that's helpful. Yeah, I was picturing more like a car owner's manual where it has endless diagrams to help people who haven't used a car radio before.

If the hydraulic system will lift the FEL bucket and the 3pt implement and keep them there long enough to drive a few miles home - even if you have to keep lifting them as you go - then you probably have enough good left in the hydraulic system to be able to fix it up once you get to your shop.

It's not optimal, but I strongly doubt you are going to find much better for that price.

Awesome, that's what I was trying to find out.

But get ready for a month of greasy evenings getting the maintenance going in the right direction. If you aren't into that, don't bother to get started. And even so, you may run into a problem that means scrapping the project for what you can get out of the FEL. So be honest with yourself about your time.

Far as I'm concerned that's part of making it my own...

Thanks again.