/ After replacing hydraulic pump seal & o-rings hitch not raising correctly - JD 850
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After replacing hydraulic pump seal & o-rings hitch not raising correctly - JD 850
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rScotty
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Re: After replacing hydraulic pump seal & o-rings hitch not raising correctly - JD 85
That could have been it. From your photos, something sure caused a lot of wear. I'd say the most common cause of wear in a pump that is properly primed is assembling it with the wrong shims or parts in the wrong places, after that is heat from dragging or mis-assembled seals, and somewhere way down the list must be dirty fluid - but I've not actually seen the last one - dirty fluid - often enough to recognise it.
Priming a pump is one of those things that is so necessary - especially when a pump sits above the fluid surface - that we old mechanics are probably all guilty of not discussing it enough. I'm going to try to rectify that in retrospect by beating the subject into the ground right now. Anyone else please chime in too.
First of all, a pump ought to prime itself - but don't ever make the assumption that it has because doing so will cost you a pump someday.
The problem is simple: The pum needs to have fluid in itself form the start, because fluid in the pump provides the seal necessary for it to prime itself. It's a dog chasing it's tail.
My suspicion is that even when a pump is perfect and installed right that there is a lot of wear due to running dry or nearly dry as it is priming itself. And that isn't just for new installations. It's got to apply to some extent any time that a tractor sits for a month or more without being started. I'd betcha that's where a pump wear happens...i.e. from startup after just sitting.
Yes, a really good tight pump should create enough suction to prime itself - although I see it as a gambling game as to whether any pump will prime itself before some wear happens. It helps if the fluid reservoir is clear full, the fluid not too cold & thick, and the fluid reservoir vent is clean. Clean filters may play a role in priming, too. Expecially in cold weather.
A replacement pump has all the same requirements. Any fluid pump that sits above the surface of the fluid reservoir has to be primed before running. And then we all just have to hope that our pump has tight enough clearances to maintain it's prime after sitting for a month.
My favorite way to prime after a rebuild is first look at the inlet and outlet hoses and try to arrange them so that when the inlet is connected between pump and reservoir there isn't any any radica bend making al high point where a big air bubble could form. Then I connect the outlet hose to the pump and hold it up in the air so that it doesn't have a high point for trapping bubbles, and pour fluid into the far end of the outlet hose until it runs all over the place. After that happens, I put my oily thumb over the now oily outlet hose end and connect it to where it is going - often that is to a hydraulic valve body for the loader - and in doing so try to lose as little fluid as possible.
And then I just hope that I've sucessfully primed it because if there is any way to know for sure. Or if there is, I haven't found it after 50 years of mechanics. But after doing what I said, I do know that know that at least I've gotten some oil into the pump enough to protect the fine polished surface it for a few seconds.
Then I start the motor and IMMEDIATELY start working levers like a demented bagpipe player to expel air from the system and make sure I have smooth pressure. IMPORTANT: If I don't see constant good pressure IN ABOUT 15 SECONDS I know I'm now in the time frame where the pump is taking some damage. I'm panicking now, because if I don't see flow in another few seconds I definitely shut it down and repeat the entire priming process. Sometimes it takes several priming cycles. I don't know why.
BTW, all of our Yanmars - and all compacts except some of the high end JDs - have an OPEN HYDRAULIC circuit. That means they DO NOT have an accumulator to maintain pressure. It also means that the hydraulic return line to the reservoir is very low or no pressure. Often that return line is nothing more than a hose with hose clamps - it might even be a length of garden hose. You can use a clear hose for that return line and that lets you see if things are flowing. And for the pressure line out of the pump, put a "Tee" in the line and add a pressure gauge. I like to use a 4 or 5 thousand PSI liquid-filled gauge mounted where I can see it when operating the loader or 3 point. Price for the gauge is about fifteen bucks. Pressure thoughout the pressure side of the system is roughly the same - although it drops momentarily when a cylinder is working. Expect normal pump pressure to be somewhere between 1800 and 2800 psi for our Yanmars.
Old farm tractors from 50 years ago had pumps with larger tolerances and often ran as low as 900 to 1200 psi. for hydraulic pressure. That is still enough to do real work.
Pumps run warm and sometimes almost hot. That's a problem with hydraulic systems. They work by shearing oil and pumping it against resistance so heat is generated. However, a pump that runs too hot to comfortably put your hand on hot is wrong - and probably already damaging itself. Although on big farm machinery I've seen them run hot like that for an entire harvesting season. But NOT on a compact. Maybe the farm machinery gets away with being so hot because they have huge hydraulic reservoirs to cool the fluid just enough. 20 gallon hydraulic fluid reservoirs aren't uncommon at all.
As for seal drag, a brand new pump has a slight drag due to the seals. It isn't much drag when you turn the shaft with your fingers, but you can feel that slight drag of new seals. A used but still good pump can have almost no drag at all when you spin the shaft with your fingers. Even an old style funky PTO-driven gear pump that has low pressure and high volume has very little drag - and it is about as crude as a pressure pump gets. A compact tractor's internal hydraulic pump is much higher pressure and closer tolerances than a PTO-driven pump.
There....I've beat the subject just about enough for me. Now it's someone else's turn. Sorry about your pump.
rScotty
That could have been it. From your photos, something sure caused a lot of wear. I'd say the most common cause of wear in a pump that is properly primed is assembling it with the wrong shims or parts in the wrong places, after that is heat from dragging or mis-assembled seals, and somewhere way down the list must be dirty fluid - but I've not actually seen the last one - dirty fluid - often enough to recognise it.
Priming a pump is one of those things that is so necessary - especially when a pump sits above the fluid surface - that we old mechanics are probably all guilty of not discussing it enough. I'm going to try to rectify that in retrospect by beating the subject into the ground right now. Anyone else please chime in too.
First of all, a pump ought to prime itself - but don't ever make the assumption that it has because doing so will cost you a pump someday.
The problem is simple: The pum needs to have fluid in itself form the start, because fluid in the pump provides the seal necessary for it to prime itself. It's a dog chasing it's tail.
My suspicion is that even when a pump is perfect and installed right that there is a lot of wear due to running dry or nearly dry as it is priming itself. And that isn't just for new installations. It's got to apply to some extent any time that a tractor sits for a month or more without being started. I'd betcha that's where a pump wear happens...i.e. from startup after just sitting.
Yes, a really good tight pump should create enough suction to prime itself - although I see it as a gambling game as to whether any pump will prime itself before some wear happens. It helps if the fluid reservoir is clear full, the fluid not too cold & thick, and the fluid reservoir vent is clean. Clean filters may play a role in priming, too. Expecially in cold weather.
A replacement pump has all the same requirements. Any fluid pump that sits above the surface of the fluid reservoir has to be primed before running. And then we all just have to hope that our pump has tight enough clearances to maintain it's prime after sitting for a month.
My favorite way to prime after a rebuild is first look at the inlet and outlet hoses and try to arrange them so that when the inlet is connected between pump and reservoir there isn't any any radica bend making al high point where a big air bubble could form. Then I connect the outlet hose to the pump and hold it up in the air so that it doesn't have a high point for trapping bubbles, and pour fluid into the far end of the outlet hose until it runs all over the place. After that happens, I put my oily thumb over the now oily outlet hose end and connect it to where it is going - often that is to a hydraulic valve body for the loader - and in doing so try to lose as little fluid as possible.
And then I just hope that I've sucessfully primed it because if there is any way to know for sure. Or if there is, I haven't found it after 50 years of mechanics. But after doing what I said, I do know that know that at least I've gotten some oil into the pump enough to protect the fine polished surface it for a few seconds.
Then I start the motor and IMMEDIATELY start working levers like a demented bagpipe player to expel air from the system and make sure I have smooth pressure. IMPORTANT: If I don't see constant good pressure IN ABOUT 15 SECONDS I know I'm now in the time frame where the pump is taking some damage. I'm panicking now, because if I don't see flow in another few seconds I definitely shut it down and repeat the entire priming process. Sometimes it takes several priming cycles. I don't know why.
BTW, all of our Yanmars - and all compacts except some of the high end JDs - have an OPEN HYDRAULIC circuit. That means they DO NOT have an accumulator to maintain pressure. It also means that the hydraulic return line to the reservoir is very low or no pressure. Often that return line is nothing more than a hose with hose clamps - it might even be a length of garden hose. You can use a clear hose for that return line and that lets you see if things are flowing. And for the pressure line out of the pump, put a "Tee" in the line and add a pressure gauge. I like to use a 4 or 5 thousand PSI liquid-filled gauge mounted where I can see it when operating the loader or 3 point. Price for the gauge is about fifteen bucks. Pressure thoughout the pressure side of the system is roughly the same - although it drops momentarily when a cylinder is working. Expect normal pump pressure to be somewhere between 1800 and 2800 psi for our Yanmars.
Old farm tractors from 50 years ago had pumps with larger tolerances and often ran as low as 900 to 1200 psi. for hydraulic pressure. That is still enough to do real work.
Pumps run warm and sometimes almost hot. That's a problem with hydraulic systems. They work by shearing oil and pumping it against resistance so heat is generated. However, a pump that runs too hot to comfortably put your hand on hot is wrong - and probably already damaging itself. Although on big farm machinery I've seen them run hot like that for an entire harvesting season. But NOT on a compact. Maybe the farm machinery gets away with being so hot because they have huge hydraulic reservoirs to cool the fluid just enough. 20 gallon hydraulic fluid reservoirs aren't uncommon at all.
As for seal drag, a brand new pump has a slight drag due to the seals. It isn't much drag when you turn the shaft with your fingers, but you can feel that slight drag of new seals. A used but still good pump can have almost no drag at all when you spin the shaft with your fingers. Even an old style funky PTO-driven gear pump that has low pressure and high volume has very little drag - and it is about as crude as a pressure pump gets. A compact tractor's internal hydraulic pump is much higher pressure and closer tolerances than a PTO-driven pump.
There....I've beat the subject just about enough for me. Now it's someone else's turn. Sorry about your pump.
rScotty
normde2001
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- Mar 10, 2002
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Re: After replacing hydraulic pump seal & o-rings hitch not raising correctly - JD 85
what he said
. . . How many of y'all know that rogerscotty was the guy that got us a Yanmar forum on tractorbynet back in 2001?
what he said
. . . How many of y'all know that rogerscotty was the guy that got us a Yanmar forum on tractorbynet back in 2001?Re: After replacing hydraulic pump seal & o-rings hitch not raising correctly - JD 85
Didn't know that, didn't come along until 2009 but have been aware of his knowledge since then.
what he said
Didn't know that, didn't come along until 2009 but have been aware of his knowledge since then.
dfkrug
Super Member
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- Feb 3, 2004
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- Santa Cruz Mtns, CA
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- 05 Kioti CK30HST w/ Prairie Dog backhoe, XN08 mini-X
Re: After replacing hydraulic pump seal & o-rings hitch not raising correctly - JD 85
Yeah, your pump has been ruined. The gear teeth are scratched on the tips, but the body is much worse, as you can see.
Also note that the gear shaft is scored. That is a bit surprising, and points to dry assembly. They make special
assembly grease for engines if just assembling with oil is not deemed adequate. Priming, as mentioned, gets around
this problem since the intake plumbing to the pump is all empty and takes time to fill.
As for why the pump may have been failing before the rebuild, there are several possibilities, including overheating,
dirty or low oil, and suction problems caused by clogged inlet screen filter or leaky intake manifold. Or age/hours.
My 955 and 4300 tractors used a fairly low-mounted pump, but had rubber pump intake manifolds that get old and can leak,
causing air entrainment. The pumps were low enough to be below the oil level in the tank.
Also, how do the gears look? If y'all wouldn't mind, could you point out what I should be looking for on
the gears so I'll know next time? They do look worn on the edges. Other than that I'm not sure what I'm looking for.
Yeah, your pump has been ruined. The gear teeth are scratched on the tips, but the body is much worse, as you can see.
Also note that the gear shaft is scored. That is a bit surprising, and points to dry assembly. They make special
assembly grease for engines if just assembling with oil is not deemed adequate. Priming, as mentioned, gets around
this problem since the intake plumbing to the pump is all empty and takes time to fill.
As for why the pump may have been failing before the rebuild, there are several possibilities, including overheating,
dirty or low oil, and suction problems caused by clogged inlet screen filter or leaky intake manifold. Or age/hours.
My 955 and 4300 tractors used a fairly low-mounted pump, but had rubber pump intake manifolds that get old and can leak,
causing air entrainment. The pumps were low enough to be below the oil level in the tank.
/ After replacing hydraulic pump seal & o-rings hitch not raising correctly - JD 850
#26
Re: After replacing hydraulic pump seal & o-rings hitch not raising correctly - JD 85
Woah, excellent information in these posts! rScotty, I really appreciate the in-depth explanations as I'm not only trying to repair the tractor but want to understand at least the basics of the mechanical side.
Dfkrug thank you also for pointing out what to look for on the gears. I see the damage on the gear shafts where they'd fit into the bushings.
I will definitely put all of this information to use once I get the new pump. I spoke with Hoye and even the gentleman there said there's no need to prime these but after seeing what could happen in just a few minutes and the price tag that comes with it I'll definitely be priming it.
The problem arose only after rebuilding the pump so based on the information y'all have provided it seems that running it dry caused the issues. Thanks again for the help and explanations. Truly is appreciated.
Woah, excellent information in these posts! rScotty, I really appreciate the in-depth explanations as I'm not only trying to repair the tractor but want to understand at least the basics of the mechanical side.
Dfkrug thank you also for pointing out what to look for on the gears. I see the damage on the gear shafts where they'd fit into the bushings.
I will definitely put all of this information to use once I get the new pump. I spoke with Hoye and even the gentleman there said there's no need to prime these but after seeing what could happen in just a few minutes and the price tag that comes with it I'll definitely be priming it.
The problem arose only after rebuilding the pump so based on the information y'all have provided it seems that running it dry caused the issues. Thanks again for the help and explanations. Truly is appreciated.
/ After replacing hydraulic pump seal & o-rings hitch not raising correctly - JD 850
#28
