Hydraulics Diagnosis

[Estif]

I have a John Deere 950 with a third-party loader of unknown make. I've been experiencing a hydraulic problem, and I'd like to ask for any suggestions. I have the JD service manual, and think it's quite good, but when it comes to the hydraulics I just don't have all the special test equipment that seems to be at the core of the troubleshooting section.

The FEL and 3pt operation has been slow, jerky, and getting worse over the last few weeks. This past weekend operation was so very slow that I didn't even try to take it out and do any work. This is Alabama, so it's pretty hard to blame it on cold. Besides, I've used the tractor with snow on the ground and the ground itself frozen, so temps in the 50s shouldn't be causing any trouble.

Here's what I know, in order that it comes to mind:
1. Slow and jerky operation raising either the FEL or 3pt (box blade). Lower just fine.
2. Dumping and curling are also slow and jerky. Sometimes when dumping the bucket just stops and won't go any farther. If I curl and dump, curl and dump, it will eventually go on past that point like it should.
3. On a couple occasions when I put the bucket on the ground and then try to dump, an operation that normally picks the front wheels off the ground with no trouble, I notice that the bucket forces the loader arms up instead of raising the tractor. Then if I lower the arms, there's a long wait when it seems like nothing is happening, but then it will very slowly lift the front wheels.
4. I don't have a float position on the FEL.
5. I've tried just sitting and running the FEL and the 3pt up and down, thinking maybe to work the problem out. This has grown less and less effective (it takes longer and longer to get to smooth operation). Weekend before last it never did smooth out in 2-3 hours operation. Transmission was warm to the touch. Transmission is also the hydraulic reservoir on this tractor.
6. I use JD's recommended fluid, and the level's where it should be.
7. New fluid and filters about 50 hours ago. That's supposed to be a 600-hour service interval.
8. I don't hear the relief valve open while these symptoms are occurring.
9. I have noticed a hissing sound, and this weekend found that it seems to come from the hydraulic pump, or at least that area.
10. System relief valve is at the rockshaft.
11. Someone suggested air in the system, but I can't figure how it would get there, because I haven't had the system open except at the dipstick since before I serviced the filters 50 hours ago. And if air were in the system, I thought all the raising and lowering would work it out. Instead things are getting worse.
12. Engine starts right up and runs fine, doesn't seem to be loaded or anything.

That's all I can think of. Any hints, suggestions, questions of symptoms I may have missed?

Thanks,

Steve

 

[RoyJackson]

It sure does sound like air in the system.
I've no idea what would be involved in bleeding your system, but I strongly suggest you replace the hydraulic fluid (might be worthwhile having the system flushed, as well) and the filter.
Unlike liquids, air compresses... That could explain the jerky and slow motion you've described.

 

[kubmech]

Check for a suction line leak, it may look like a small amount of fluid or build up in the area of the leak. It also could be the hyd pump is going out. Both of these things can cause oil foaming hence the air in the sytem causing what you describe when curling the bucket against the ground and the loader boom moving up. What does the fluid look like after you run it for a while? If it looks milky then you have air. It could also be water contaminated. The best way to tell the difference is to drain some out. Let it sit for a while (sometimes it takes till overnight) If it clears up and there is no water at the bottom of the container then it's just air. If there is no obvious suction leak and your filters are clean (you did check/clean the suction filter located at the left rear side of the tractor) then the problem could be the hyd pump.

 

[bky]

i am by far no hydro exert but to mee sounds as if the pump is going out

 

[Soundguy]

That suction filter is a must, for cleaning. We were experiencing problems on my fathers jd 2240.. seems the mechanic had always been servicing the regular filters, but never pulled the suction side 'tube'.. was nearly solid...

This sounds almost like a started out pump... that is bad... as it will cause cavitation... and cavitation will eat a pump up quick.. sounds like this may have already happened to some degree.

Soundguy

 

[Estif]

Thanks for the suggestions, guys. I do know about the suction filter, and had it out and cleaned it when I changed the fluid 50 hours back.

I'll be:
1. Looking for suction line leaks. I did look for leaks a little Saturday, but can certainly look a little more and a little closer.
2. Run it for a while and then drain some fluid for a look.
3. Maybe pull the lines at the pump for a look at the o-rings.
4. Worry about needing a pump.

Thanks again,

Steve

 

[Soundguy]

We'll be here, waiting to here what you found.
Hopefully we can come up with a treatment for you... and hopefully it isn't expen$ive.

good luck, and Happy thanksgiving to all!

Soundguy

 

[heehaw]

looks like its time to pull the filters and if your tractor has it, the screen: and see if theres anything there that shouldn't be; what you describe happened to me on my JD1020 when the brakes went bad and stopped up the screen and filters for the hyd system; but when i removed the screen and filters, it was pretty obvious what the problem was. are your brakes making any noise?
heehaw

 

[Estif]

No, no brake problems.

Progress for tonight: Wiped all the lines down in hope of making any leak a little easier to find. Ran the tractor a little more than an hour, raised and lowered the FEL and 3pt a few times, shut down and drained out about a quart of hydraulic fluid. The fluid was full of little air bubbles, and may be a shade darker than new. Not sure about that. Left the jar of fluid to sit and see if it seperates while I do Thanksgiving.

My next step, I think, will be to drain the fluid and have a look at the filters.

Thanks,

Steve

 

[tiltbed]

Steve,Kinda courious as to what you came up with.My Ford 3000 has the same kinda problems.ie: conflict between the loader and 3 pt.I thought my problems was the slave block for the loader...o-rings and ports seemed clean.Next step is removing the suction filter in the houseing.If not that will check hoses for a switched hose...last resort (ulp) would have to be something internally for the 3pt (bypassing)...Sid

 

[Hydraman]

Don't know about the CUT's-- but on my 3020 the hydraulic pump is mounted in front of the engine, and has two 3/4" lines going to it from the rear of the tractor. In order for the pump to get oil there is another pump inside the tranny/hydraulic reservoir to move the fluid to the front of the tractor/hydraulic pump. If this "charging pump" goes bad, it could react the way you described. But, I would definately check the screen and filter first! On my 3020, when the filters are changed, I only lose the amount of oil to refill filter case while doing it. But, when cleaning screen, ALL the fluid drains out. So, make sure to have drain pan large enough to hold all the fluid when checking screen. On my 3020, when I clean the screen, I attach a shop vac to the filler and turn it on; then, when I pull the screen-- the vac keeps the fluid from draining out!!! Don't know if this little trick will work for you, or not. Good luck! Don

 

[Anonymous Poster]

symptom #3 definitely indicates air in the cylinders, and when combined with the other symptoms, indicates a lot of air in the cylinders.
You may also have a lo flow situation or lo pressure, but I'd bet on air being the major problem.

 

[Estif]

Just came in from draining the fluid, taking off all the filters, and then taking off all the suction line between the reservoir/transmission and the pump.

1. The screen does have some odd, small globs on it. Like maybe some bits of dirt fell in when I was checking the dipstick.
2. O-rings are all in good shape, and everything was tight. I'll be replacing the o-rings anyway, long as I'm in there.
3. I didn't start the tractor up at all, but there were still bubbles in the drained fluid. Guess this is just from making the drop from the transmission into the bucket.
4. The filter - not the screen, this one looks like an oversize oil filter - screws onto a mounting, of course, that is inline with the suction line. The suction line is rigid. The connections at the mount are compression fittings. May just be my lifelong loathing for compression fittings, but that's the only part of the line that makes me even a little suspicious. But there's no sign of a leak, even there.

So, now what? Put everything back together, new filters, new fluid, and see if it works? Should the air that's going to be in there as a result of opening all this up just work its way out? Likewise, should the air that's probably still trapped in the cylinders just work it's way out if everything's sealed up where it should be? That's my understanding of how it's supposed to work in an open system like this, that it doesn't need bleeding like on automotive brakes?

Steve

 

[kubmech]

O.k. Steve, looks like everything checks out as far as the delivery system is concerned. Now the next step would be to flow test the pump. However, most guys don't usually have a flow meter laying around the garage so......You have a couple of options. Put it all back together and give it a try (yes running all your hyd functions against relief should bleed out all the air) Listen to the pump while you are operating the hyd's. Is it making any noise, does it get hot to the touch real fast? Do the hyd's even build enough power to open the relief valve and bog the engine? Should get about a 300-500 rpm drop off when hitting relief (say bucket curled all the way back and hold it there) if you are not getting that then I would have to say the pump is the problem. That's about the best way to tell if the pump is the problem. The other option is to remove the pump and dissasemble it carefully. Look at the aluminum housing (the gears will most likely look good) is it erroded wear the gears ride? if you can click your nail on the ridge then that would confirm the bad pump. Another option (if the spin on filter is on the return side, can't remember on the 950) you can cut that open and check for aluminum particles. That is also a good sign of pump failure. You can even check for that by draining the trans at the lowest point, depending on wear the filter is in the system. And see if any aluminum particles collect in the drain pan. They will be very fine. At this point, I would suspect the hyd pump.

 

[Estif]

Found the problem, I believe. Tuesday night I didn't have all the fluid and filters needed to reassemble and try it out, so I decided to go for pulling the pump off. First, though, I did cut the spin on filter open and found very small amount of aluminum filing. So, took the pump off and found it has a coupling on the shaft that mates with something inside the engine. The service manual said "remove the nut and washers on the end of the shaft and remove the coupling." Sounds good, except the coupling wouldn't budge. While prying and beating, I managed to break the shaft off the pump, leaving it stuck in the coupling. Thought, well, whether the pump was dead before or not, it surely is now. This morning I took the coupling and showed it to a mechanic at the JD dealer. He knocked the shaft out and we found that the key had sheared, allowing the coupling to spin on the shaft, giving intermittent pumping, apparently. That is, it spun under torque from the engine. To hand pressure, it was like a press fit.

I do appreciate all your assistance here, all of you. I have a pump on order and will post when I get things put back together.

Steve

 

[kubmech]

Glad to see you found the problem. I am curious what the inside of the pump looks like, so if you get a chance?/w3tcompact/icons/wink.gif?

 

[bgott]

If it doesn't fit, force it! If it breaks, it needed replacing anyway!/w3tcompact/icons/grin.gif Glad you found your problem. Sometimes, in spite of using any and all diagnostic procedures, you just have to take stuff apart and look at it to find the problem.

 

[Estif]

No problem. I'm posting a picture of the disassembled pump. Or at least trying to. Insides look pretty normal. Gears are pristine, bushings look fine. Very fine ridge in just a couple spots around the holes where the gear shafts or bushings contact the aluminum cover. May be a little ridge in the wall of the body where two of the bushings are - at least I can't get them out. The gear with the longer shaft is the one that I broke off...it was a couple inches longer still.

Just got the pump back on tonight, but the plumbing's still all over the floor. Christmas is ten days away, I've been making presents at a fairly frantic pace.

Oops, it says my picture's too big, and I can't figure out how to make it smaller. Sorry.
Thanks,

Steve

 

[Estif]

Rejoice, I have good tidings of great joy! Well, besides the much greater tidings of much greater joy announced by the angels...

Last workday of the year for me was yesterday, so today I finally put all the hydraulics back together - and it works! Faster and smoother than I can remember! There will be some seat time catching up with things after I get back from the family gatherings!

Thanks again,

Steve