Onboard Hydraulic Grenade

   / Onboard Hydraulic Grenade #1  

chrisinnh

Member
Joined
May 18, 2007
Messages
46
Hello!

The onboard hydraulic pump on my B7100 died last night. You can see a long crack just below the pump's equator in the following picture:

crack.med.jpg


Some circumstances of the failure:

  1. This is the first time I've used the onboard hydraulics to power the loader.
  2. The transmission was filled about 50/50 with gear oil and UDT substitute from TSC.
  3. I was raising the empty bucket at the moment of failure.
  4. The transmission may have been overfilled.

Any idea what could cause such a failure? The tractor has less than 800 hours on it.

Here's a sketch of how I plumbed my hydraulic system for the loader:
hydraulic.gif

Any clues about what might have gone wrong?

Can somebody recommend a favorite salvage yard where I can source a used pump?

Thanks very much.

/chris
 
   / Onboard Hydraulic Grenade #2  
I'm no expert hydraulic or otherwise, but seems that gear oil would be to thick, maybe that had something to do with the failure?

I'm sure guys with more experience will give a more thorough answer

good luck...
 
   / Onboard Hydraulic Grenade
  • Thread Starter
#3  
irwin said:
I'm no expert hydraulic or otherwise, but seems that gear oil would be to thick, maybe that had something to do with the failure?

Gear oil was the original spec for this application.

Later they changed it to UDT. This pump ran in 80wt all last winter with no problem, but I never asked it to do any work.

/chris
 
   / Onboard Hydraulic Grenade #4  
I'm not an expert by any means but two questions come to my mind:
Does the loader valve an allow flow back to tank when it's in neutral?
Do you have a relief valve in the loader system?
 
   / Onboard Hydraulic Grenade
  • Thread Starter
#5  
claridon said:
Does the loader valve an allow flow back to tank when it's in neutral?

The loader valve causes fluid to flow back into the transmission at all times.
In neutral, it's just an open circuit.
When moving a cylinder, the drain from the other side of that cylinder goes back to the trans.

claridon said:
Do you have a relief valve in the loader system?

Yep, it's part of the loader valve.

/chris
 
   / Onboard Hydraulic Grenade
  • Thread Starter
#6  
Something I didn't mention, but the question about a relief valve got me thinking about it:

The motor was at about 50% throttle at the time of the failure.

I would expect this pump to be able to stall the motor under a substantial hydraulic load.

...But nothing of the sort happened. The motor was not under load at the moment of failure.

I'm planning to take things further apart tonight. It looks like it will be a real challenge to get to the back mounting bolts. Hopefully I will have autopsy photos tomorrow.

/chris
 
   / Onboard Hydraulic Grenade
  • Thread Starter
#7  
Autopsy Update:

Removing the pump turned out to be easier than I thought it would, once I got the hydraulic lines, throttle linkage, fuel fiter and brackets out of the way.

The filter screen on the intake side was intact and clean. I don't think anything nasty could have gotten into the pump.

...And the pump looks good inside too (except for the crack). There's no carnage on the pump housing or gears, and the pump turns easily by hand.

I'm disappointed that nobody has suggested what I might be doing wrong. I've sourced a used pump for $150, and sure would be bummed if I repeat some stupid mistake and wind up killing this this replacement unit too.

Ideas?

Here are some pictures of the housing:

IMGP4281.med.JPG

IMGP4282.med.JPG

IMGP4283.med.JPG

IMGP4284.med.JPG

IMGP4285.med.JPG


/chris
 
   / Onboard Hydraulic Grenade #8  
chrisinnh said:
Autopsy Update:
I'm disappointed that nobody has suggested what I might be doing wrong. I've sourced a used pump for $150, and sure would be bummed if I repeat some stupid mistake and wind up killing this this replacement unit too.

Ideas?

/chris

Yo, chill lil' brother. We're here to help. Not everything is black and white. That pump could have failed for any number of reasons. You were the one operating it at the time. If you don't know what happened, how are we?

It's hard telling what happened to your pump. I don't see any scoring of the internal surfaces. Did it make a "Pop" noise when it blew? What were the exact circumstances from one second before it blew to one second after? Exactly how long did you have the lever pulled before you noticed a problem? All of this info is very important. The more details, the better. If there was a pop, I would bet on your pump dead-heading. Especially with no internal scoring. There is a company called Attica Hydraulics that specializes in this type of stuff. You may want to give them a call. Real nice pics by the way.
 
   / Onboard Hydraulic Grenade #9  
Can you tell us some info about the history of the control valve? Is it new? Is the relief valve visible and intact? The pump housing fracture looks like what happens when there is NO relief valve functioning in the system. This can happen when the in and out ports are reversed at the control valve so the relief valve is beyond the load instead of before it. Everything would seem ok until oil was directed to a circuit that was at the end of its travel and couldn't move (dead headed). Then something would have to give - usually a hose blows, or the pump seals extrude out around the shaft - leaking oil into the engine, or maybe the pump housing burst from the pressure spike. As always, prompt cheerful refund if info is bogus. Good luck.
 
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   / Onboard Hydraulic Grenade #10  
I'm no expert but I'd have thought that bad or faulty plumbing would have blown a hose (or some other weak spot) before it would crack a casting. Are there any hoses between the pump and any obstructions?. If so, and the hoses are still intact, then it may be just a bad casting.
 
 
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