753 pump *hums*

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Tazza

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I have a "new to me" 753. It had injection problems which i managed to sort out after someone sabotaged it!. It also had a drive problem on the left side. Before i attacked the motors when running, the hydraulic pump would let out a hum which I'm sure isn't rite. I thought it may just be air so i pulled both drive motors and found on one side the seals were like powder. I replaced them and re-installed the motors today. Re-filled the tank, it drives great but that hum is still there. At low idle its not there but if you lift the arms and let them fall it hums as it drops. Increase the revs and it hums again. The only thing i can think of is the charge pressure relief is causing the noise, but not sure.
Any ideas on what it could be? I had a 743 that would do this from time to time, but i never did find out what the noise was from.
 

73Eldo

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The 753 just has one pump? (Im still new to this skid steer thing) I had a tractor that would make a noise like that sometimes. Messing with the control valve levers would stop it so I always suspected something in the valve was weak or worn and sometimes causing enough restriction in the flow to start to load the pump then it would bypass or seat (whatever it was supposed to be doing) and it would quit till the pressure came up (or down) again and start the whole cycle over again. Same tractor had some fancy regulation thing on the 3 point that would actually make the tractor start jumping off the ground.
 
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Tazza

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The 753 just has one pump? (Im still new to this skid steer thing) I had a tractor that would make a noise like that sometimes. Messing with the control valve levers would stop it so I always suspected something in the valve was weak or worn and sometimes causing enough restriction in the flow to start to load the pump then it would bypass or seat (whatever it was supposed to be doing) and it would quit till the pressure came up (or down) again and start the whole cycle over again. Same tractor had some fancy regulation thing on the 3 point that would actually make the tractor start jumping off the ground.
It actually runs 3 pumps, one for each drive motor and one for he main hydraulics. It sounds like its the hydraulic pump as when i load it down it still makes the noise... I will need to investigate a bit more i think.
 

Fishfiles

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It actually runs 3 pumps, one for each drive motor and one for he main hydraulics. It sounds like its the hydraulic pump as when i load it down it still makes the noise... I will need to investigate a bit more i think.
can you make the hum change tones and go away by moving the travel sticks forward and or reverse
 
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Tazza

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can you make the hum change tones and go away by moving the travel sticks forward and or reverse
The noise is constant at anything over idle, moving the sticks doesn't change things. I need to try and record the sound and talk to my dealer..... I need to adjust the park brake so i can run it with the cab in the air and see if i can work out where the noise is coming from, it sounds like the hydraulic pump.
 

Fishfiles

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The noise is constant at anything over idle, moving the sticks doesn't change things. I need to try and record the sound and talk to my dealer..... I need to adjust the park brake so i can run it with the cab in the air and see if i can work out where the noise is coming from, it sounds like the hydraulic pump.
by you saying you need to adjust the brake it makes me further believe your steering adjust is out of wach , they will make a humming sound if not properly neutraled and when idled up will change tune and sometimes go away , if it pulling against the brake it's got to be making some terrible sounds , usually you can pull one lever one way and the other lever te other way and find the sweet spot to quiet it down , sometimes the pintle lever is loose on the tranny shaft and you can't get it to stop by moving levers, I think that is your problem the pintle lever , most probally the left side sitting in the seat ,. is loose as the left one is most common
 

skidboy

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by you saying you need to adjust the brake it makes me further believe your steering adjust is out of wach , they will make a humming sound if not properly neutraled and when idled up will change tune and sometimes go away , if it pulling against the brake it's got to be making some terrible sounds , usually you can pull one lever one way and the other lever te other way and find the sweet spot to quiet it down , sometimes the pintle lever is loose on the tranny shaft and you can't get it to stop by moving levers, I think that is your problem the pintle lever , most probally the left side sitting in the seat ,. is loose as the left one is most common
If you have an early 753,they had a problem with a cold weather by-pass valve. It is in the side of the control valve and the poppet wears on an angle into it's seat. When the machine warms up it is not as bad. Just a thought.
 
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Tazza

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If you have an early 753,they had a problem with a cold weather by-pass valve. It is in the side of the control valve and the poppet wears on an angle into it's seat. When the machine warms up it is not as bad. Just a thought.
It doesn't *seem* to be the hydrostatic pumps, i can move my levers and the noise is still there, its not the usual groan you hear when the pump is fighting the motors when the park brake is engaged.... The brake is so far out of adjustment you can drive it around with the brake on! I will need to set neutral and adjust the brake over the next few days.
skidboy - you may be on to something, i had a fiddle today and the tube line that comes from the oil cooler and filter to the control block is the one that is humming, I'm wondering of my filter is plugged and thats the oil going over the high pressure by-pass valve or not. I'm going to grab a filter anyway. Do you remember just where this cold weather by-pass valve is on the control block?
 

Fishfiles

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It doesn't *seem* to be the hydrostatic pumps, i can move my levers and the noise is still there, its not the usual groan you hear when the pump is fighting the motors when the park brake is engaged.... The brake is so far out of adjustment you can drive it around with the brake on! I will need to set neutral and adjust the brake over the next few days.
skidboy - you may be on to something, i had a fiddle today and the tube line that comes from the oil cooler and filter to the control block is the one that is humming, I'm wondering of my filter is plugged and thats the oil going over the high pressure by-pass valve or not. I'm going to grab a filter anyway. Do you remember just where this cold weather by-pass valve is on the control block?
the filter could be clogged up or it could be the wrong micron mesh filter , does it have a bobcat filter , when crossing over the hydraulic filter with aftermarket care has to be taken as there are many different micron meshes in the same filter housing ----------if that 753 has BOSS , I think it should flash you a code if the filter was plugged
 

skidboy

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the filter could be clogged up or it could be the wrong micron mesh filter , does it have a bobcat filter , when crossing over the hydraulic filter with aftermarket care has to be taken as there are many different micron meshes in the same filter housing ----------if that 753 has BOSS , I think it should flash you a code if the filter was plugged
The valve is a fitting about 2" long and from memory is screws into the side of the control valve up the top (if that makes sense) I think it's the return from the control valve to the cooler.If you pull this fitting apart you will find a poppet and spring inside. I should have a pic.of this,will post if I can find it.
 
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Tazza

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The valve is a fitting about 2" long and from memory is screws into the side of the control valve up the top (if that makes sense) I think it's the return from the control valve to the cooler.If you pull this fitting apart you will find a poppet and spring inside. I should have a pic.of this,will post if I can find it.
It does have a BOSS system, the display didn't flash any codes. I thought the same, if it was plugged it should show an error from the sender. It did need changing after i saw the state of the O ring in the drive motor!!! It was just a crumbled mass (what was left of course), i have never seen an o-ring go like that before.
I changed the filter and it seems the same, I'll have a go at adjusting centre as i fiddled again tonight after i got it a little warm and it did seem to get a little quieter, so i may have to look into that a little more.
I'll look for that poppet setup, i don't remember seeing it but I'll take a better look this time.
I need to work on the tilt ram, the pressure seal is dead and i tilt the bucket and get a jet of oil!
Thanks for the ideas guys, it gives me more things to check up on. The later model machines are still new to me, but i am learning.... Slowly :)
 

heatpumpproducts

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It does have a BOSS system, the display didn't flash any codes. I thought the same, if it was plugged it should show an error from the sender. It did need changing after i saw the state of the O ring in the drive motor!!! It was just a crumbled mass (what was left of course), i have never seen an o-ring go like that before.
I changed the filter and it seems the same, I'll have a go at adjusting centre as i fiddled again tonight after i got it a little warm and it did seem to get a little quieter, so i may have to look into that a little more.
I'll look for that poppet setup, i don't remember seeing it but I'll take a better look this time.
I need to work on the tilt ram, the pressure seal is dead and i tilt the bucket and get a jet of oil!
Thanks for the ideas guys, it gives me more things to check up on. The later model machines are still new to me, but i am learning.... Slowly :)
hi tazza , i have an Lx565 new holland , and after looking for hydraulic leaks with ultrovilet light and juice , very effective once i read the directions 1 packet / 5 liters of oil .
any way . i seem to have a leek at the top of my hydrostatic pump , the one that attaches to the left hand stick . now as you mite know as i moved the stick the machine got real quite , i guess you would call it a hum , but by moving the stick only a fraction , so litle the wheels don't turn . it looks like play in what i would call push block bearings that the linkages rest in.
is thier any harm in this hum . also the oil seems to be comming out around the top from hydrostatic pump shaft surounded by a cap ( kind of an oval brass coloured pressed plate )
and thier is also a small leak at the top of the control bank , i think these plugs are called checks , any way its the center one , is thier any thing i need to know before i disturb this ,
and are the two things related some how , and also the bucket would not stay up at all .slowly dropping and would not hold it self up . would fixing this check have something to do with that .any sugestions .thanks .kier
 
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Tazza

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hi tazza , i have an Lx565 new holland , and after looking for hydraulic leaks with ultrovilet light and juice , very effective once i read the directions 1 packet / 5 liters of oil .
any way . i seem to have a leek at the top of my hydrostatic pump , the one that attaches to the left hand stick . now as you mite know as i moved the stick the machine got real quite , i guess you would call it a hum , but by moving the stick only a fraction , so litle the wheels don't turn . it looks like play in what i would call push block bearings that the linkages rest in.
is thier any harm in this hum . also the oil seems to be comming out around the top from hydrostatic pump shaft surounded by a cap ( kind of an oval brass coloured pressed plate )
and thier is also a small leak at the top of the control bank , i think these plugs are called checks , any way its the center one , is thier any thing i need to know before i disturb this ,
and are the two things related some how , and also the bucket would not stay up at all .slowly dropping and would not hold it self up . would fixing this check have something to do with that .any sugestions .thanks .kier
I think i know the seals you are talking about on the pump, they seal the shaft for the pintle levers or yoke (whatever you want to call them). There is only charge pressure under here so i don't see it causing you any harm if you can live with the leak. The control block should be simple too. The fittings should use an o-ring for a seal, if you pull the plug there may be a check valve under it, just replace the seals and it should be good. The arms dropping could be a bad piston seal in a ram or it could be the load checks in your control block. They will look like a plug but have a poppet and a few O-rings and backup rings usually in line with the spool at either end where the tube lines connect. If you drain as much oil as possible, pull the load checks out and take them to a hydraulic seal shop they will be able to match them up for you. They are a very simple item, but when they wear and leak it drives you mad with the rams not holding pressure and the arms lower on their own or bucket tilts.
It may sound compelx but it really is simple, just a few O rings and backup rings.
 

heatpumpproducts

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I think i know the seals you are talking about on the pump, they seal the shaft for the pintle levers or yoke (whatever you want to call them). There is only charge pressure under here so i don't see it causing you any harm if you can live with the leak. The control block should be simple too. The fittings should use an o-ring for a seal, if you pull the plug there may be a check valve under it, just replace the seals and it should be good. The arms dropping could be a bad piston seal in a ram or it could be the load checks in your control block. They will look like a plug but have a poppet and a few O-rings and backup rings usually in line with the spool at either end where the tube lines connect. If you drain as much oil as possible, pull the load checks out and take them to a hydraulic seal shop they will be able to match them up for you. They are a very simple item, but when they wear and leak it drives you mad with the rams not holding pressure and the arms lower on their own or bucket tilts.
It may sound compelx but it really is simple, just a few O rings and backup rings.
the part that is leaking is the piston pump that controls the movement of the right hand stick.i was calling it the hydrostatic pump , but its the piston pump that sends fluid to the motors , i looked it up on messick last night.
it seems to be leaking from the shaft that conects to the controle linkage for that RH- stick.
looking at that , the part only rotates slowly back and forth , the seal & o-ring . don't cost very much , about how long mite it take to fix and re-adjust the lever controls .i looked at the pillow bearings for the control levers and the play in them is what seems to make the difference in the noise are these normally tight when new ? when i adjust for the noise the play is all that seems to be shifted and the HUM noise stop.
i what to know if the HUM i noticed , the same RH-stick if moved ever so slitely tackes the hum away , so little that the wheels don't move . that hum is that normal when the piston pump is ingaged by the control sticks ? i only noticed it now that the instake manifold gasket has been replaced , and the center protection plate is off , to expose the controle spools .
i will pay more attention today if both sides when ingaged make the same noise .
i can't tell you guys how much i enjoy this site , and all the feed back , and timely responces .
THANK YOU ALL.
 

mllud

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the part that is leaking is the piston pump that controls the movement of the right hand stick.i was calling it the hydrostatic pump , but its the piston pump that sends fluid to the motors , i looked it up on messick last night.
it seems to be leaking from the shaft that conects to the controle linkage for that RH- stick.
looking at that , the part only rotates slowly back and forth , the seal & o-ring . don't cost very much , about how long mite it take to fix and re-adjust the lever controls .i looked at the pillow bearings for the control levers and the play in them is what seems to make the difference in the noise are these normally tight when new ? when i adjust for the noise the play is all that seems to be shifted and the HUM noise stop.
i what to know if the HUM i noticed , the same RH-stick if moved ever so slitely tackes the hum away , so little that the wheels don't move . that hum is that normal when the piston pump is ingaged by the control sticks ? i only noticed it now that the instake manifold gasket has been replaced , and the center protection plate is off , to expose the controle spools .
i will pay more attention today if both sides when ingaged make the same noise .
i can't tell you guys how much i enjoy this site , and all the feed back , and timely responces .
THANK YOU ALL.
That hum because the sticks are very slightly opening the valve and that fluid is enough enter the pump but not enough to push it. Those pillow block bearings are cheap.
I think when you get your linkages tight and the arms centered on the pumps . The hum should stop. It took me a while to get mine just right.
I dont know if you still have a new holland. I could send you the procedure out of the owners manual.You have to adjust those linkages in a certain order. This keeps the sticks even with each other and the linkages so they push the pumps equally Mike
 
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Tazza

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That hum because the sticks are very slightly opening the valve and that fluid is enough enter the pump but not enough to push it. Those pillow block bearings are cheap.
I think when you get your linkages tight and the arms centered on the pumps . The hum should stop. It took me a while to get mine just right.
I dont know if you still have a new holland. I could send you the procedure out of the owners manual.You have to adjust those linkages in a certain order. This keeps the sticks even with each other and the linkages so they push the pumps equally Mike
Yeah, the hydrostatic pump is a piston pump. I know he part you are talking about that is leaking, it only turns like 1/8 of a turn or something. I really don't know how hard it is to change the seals, i think its pretty easy as they should be able to be pulled out from the top so you don't need to pull the pump down. You will just need the details that Mike has to re-adjust it all back to neutral. You may be lucky enough for it to all go back together and it could still be spot on.
 
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Tazza

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Yeah, the hydrostatic pump is a piston pump. I know he part you are talking about that is leaking, it only turns like 1/8 of a turn or something. I really don't know how hard it is to change the seals, i think its pretty easy as they should be able to be pulled out from the top so you don't need to pull the pump down. You will just need the details that Mike has to re-adjust it all back to neutral. You may be lucky enough for it to all go back together and it could still be spot on.
Well, i set the hydrostatic pump(s) to neutral but it still makes the same noise. It still sounds like air in the system, the aux hydraulics couplers were removed and plugs were put on, plus i re-did the tilt ram and hydro motors so air is in there still. The oil is only slightly foamy, you can see small bubbles so i can't rule out air as the problem just yet.
I couldn't find the cold weather by-pass valve either.... Nothing looked even remotely like the description. The only fittings on the control block were hoses and tube lines. It does have bucket positioning though but i don't know if thats an issue or not.
The only thing i can do is keep running it a little bit to get the air out and hope it clears up. The only thing i haven't looked at was the hydraulic line from the tank to the pump but my parts break down doesn't show any filters in here.....
Hopefully I'll figure it out!
 
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Tazza

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Well, i set the hydrostatic pump(s) to neutral but it still makes the same noise. It still sounds like air in the system, the aux hydraulics couplers were removed and plugs were put on, plus i re-did the tilt ram and hydro motors so air is in there still. The oil is only slightly foamy, you can see small bubbles so i can't rule out air as the problem just yet.
I couldn't find the cold weather by-pass valve either.... Nothing looked even remotely like the description. The only fittings on the control block were hoses and tube lines. It does have bucket positioning though but i don't know if thats an issue or not.
The only thing i can do is keep running it a little bit to get the air out and hope it clears up. The only thing i haven't looked at was the hydraulic line from the tank to the pump but my parts break down doesn't show any filters in here.....
Hopefully I'll figure it out!
skidboy - you nailed it, i found it today. Pulled it and sure enough, the seat was worn on an angle. I took the spring and poppet out and the noise was gone, the only problem was my charge pressure was also gone. But it tells me that its the problem. It appears this was not installed in later model machines as my 751s control block doesn't have this setup.
I just need to get a new seat and poppet, hopefully it will fix the problem.
 
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Tazza

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skidboy - you nailed it, i found it today. Pulled it and sure enough, the seat was worn on an angle. I took the spring and poppet out and the noise was gone, the only problem was my charge pressure was also gone. But it tells me that its the problem. It appears this was not installed in later model machines as my 751s control block doesn't have this setup.
I just need to get a new seat and poppet, hopefully it will fix the problem.
heatpumpproducts: slightly late reply, but the seal for the pintle levers is a simple lip seal, you will need to remove the centering plate, then the alloy arm that bolts to the yoke. You must fully remove this bolt to enable it to slide off the shaft. You will need to remove all 4 bolts on the cover on the top of the pump that hold the seal. You will need to replace the shaft seal and you will also need to replace the square O ring that seals the plate. It can all be done without disturbing the inside of the pump.
Slightly off topic, but here is a picture of the gland nut from the tilt ram, i had a little trouble removing it!!! ended up needing to use an air chisel and oxy torch. I was lucky enough to still have a piece of alloy that i was able to machine a new one out of, worked out pretty well. Some how the thread picked up and it refused to move. I had a 10' bar holding the body of the ram, i then used a LARGE pipe wrench with a 6' pipe and it still refused to move much more than a few mm every try. Out came the air chisel and it would move slightly every try.
100_0037.jpg

Higher rez pic: http://users.tpg.com.au/tazza_/100_0037.jpg
 
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