Jinma 284 hydraulic pump breaks loose from drive assembly

[leop]

The hydraulic pump on my Jinma 284 is held to the drive assembly (which is bolted to the back of the timing cover) by two bolts. The pump has snapped the lower of the two bolts twice in the past week. The first time the FEL was under a light load, and the second time the 3pt was under a light load.

A week prior to the first failure I blew the return hose from the FEL's spool valves. At the time I figured it was an old hose, but I now think it was the quick connect. In any event I bypassed the quick connect on the line that blew.

Of course the pump end of the shaft is now chewed up, though I don't know if happened in the few seconds after the pump broke loose and before I shut the engine off, or if it was worn down before the failure.

Has anyone seen this before? I have read threads here that speak of weak hydraulics due to a rounded off shaft, and of splitting the pump case open when the pump is deadheaded due to bad quick connects or pressure relief valve issues, but have yet to read of the pump physically breaking loose from the drive.

Does anyone have a picture and some dimensions of what the end of the pump shaft is supposed to look like? I can weld it up and then re-machine it in the mill, but I have no idea of the dimensions to machine to now that it's mangled. I suppose I should re-build the pump (new seals and such) while it's apart too. Any good threads on that task that someone could point me to?

Thanks in advance for any insight or help anyone might have on this.

Leo

 

[mrmikey]

I wonder if the pump shaft being chewed caused the drive to cam-out of the drive slot when the pump comes under and load and is breaking the mounting flanges....Mike

 

[leop]

I wonder if the pump shaft being chewed caused the drive to cam-out of the drive slot when the pump comes under and load and is breaking the mounting flanges....Mike

That could be what's happening for sure. It's snapping that bottom bolt but not the top one so the cam effect does make sense.

But why under light load? There were plenty of heavy loads prior to the second breakaway. There must be a blockage somewhere in the system?

 

[leop]

ALL GUESSES are WELCOME.

Almost all of the solutions to problems that I have posted on this board and asked for help on have come from people that had not seen my exact problem. They did however have one or several of the following valuable skills: Insight to the mechanics of my brand machine (jinma 284), insight to the system having the issue (in my case the Hydraulic system) whether from the same brand or another brand tractor, sharp minds, and good educated guesses.

So please feel free to offer any guesses that you may have. Mr. Mikey had a good one I plan to follow up on. Are there any others, or endorsements of his idea? 99% of you out there seam to know more about tractors than me so please chime in.

Besides it's fire season in California and the Fire Marshal is not going to give me much time to fix this thing before he fines me for not finishing brush clearing

Leo

 

[mrmikey]

There must be a blockage somewhere in the system?

QC's not opening all the way? the Chinese ones are note for doing that. Put a pressure gauge in the system at the outlet for the pump and see if there are any spikes...Mike

 

[quicksandfarmer]

As long as we're guessing....

I agree that you're seeing pressure spikes. What's unusual is that the bolt is what's giving, usually it's a seal or the driveshaft for the pump itself. Could it be that the pump itself is jamming, maybe something stuck inside of it? I think of how much torque you'd have to apply to the pump to get a bolt to shear and I just don't see the driveshaft withstanding that.

Far and away, the most common source of the pump dead-heading is the quick-releases. Sometimes they can separate a little bit, just enough for the ball to close. Some people take the balls out of them. They leak when detached that way but they can't ever dead-head. Some people also fasten them together with cable ties -- one around each hose and then two joining those two together -- so they can't come apart.

 

[leop]

Mike,

I am headed out now to get a high pressure T and a back-up relief valve that I plan to plumb right at the outlet of the pump with the bypass either going back to the input of the pump of back to the reservoir. Do you what the thread and hose sizes are at the inlets and outlets of the pump? I assume metric, but in the case of the QD most people recommend getting stock pioneers at TSC, which I think are not metric?

 

[mrmikey]

What's unusual is that the bolt is what's giving, usually it's a seal or the driveshaft for the pump itself

Agreed

Do you what the thread and hose sizes are at the inlets and outlets of the pump?

Fraid not

I assume metric, but in the case of the QD most people recommend getting stock pioneers at TSC, which I think are not metric?

Can't say as I've ever seen a metric QC, not saying they're not made, just never seen one. Mine are 1/2" NPT..

 

[leop]

As long as we're guessing....

I agree that you're seeing pressure spikes. What's unusual is that the bolt is what's giving, usually it's a seal or the driveshaft for the pump itself. Could it be that the pump itself is jamming, maybe something stuck inside of it? I think of how much torque you'd have to apply to the pump to get a bolt to shear and I just don't see the driveshaft withstanding that.

Far and away, the most common source of the pump dead-heading is the quick-releases. Sometimes they can separate a little bit, just enough for the ball to close. Some people take the balls out of them. They leak when detached that way but they can't ever dead-head. Some people also fasten them together with cable ties -- one around each hose and then two joining those two together -- so they can't come apart.

Yup, I suspect the quick releases. Out comes the last one today! Good idea about the pump, I'll check it when it's apart so that I can repair the shaft end.

In some ways I am much happier with a broken bolt than with a pump splitting itself open. Just seams strange that no one else has seen the same failure mechanism. Thank God I didn't get those grade eight bolts to replace the first set that broke!

Thanks for the guess quicksandfarmer.

 

[Bob Rooks]

Mike,

I am headed out now to get a high pressure T and a back-up relief valve that I plan to plumb right at the outlet of the pump with the bypass either going back to the input of the pump of back to the reservoir. Do you what the thread and hose sizes are at the inlets and outlets of the pump? I assume metric, but in the case of the QD most people recommend getting stock pioneers at TSC, which I think are not metric?

Not recommended to plumb the relief back into the suction. I know several have done this, but it's a great way to coke the hydraulic oil and toast the pump. And you don't even know you're doing it.
FWIW, I changed the quick couplers on all my equipment to the flat face style because they make up and part much easier, stay cleaner, and don't make a mess. Probably more reliable too, and they come with locks.