hydr drive motor

[Tazza]

thats maybe what the juddering is?...... sounds and feels like using a hammer drill lol???? i got a car oil pressure guage to attach is that ok?

If your sure it is accurate and will read up to about 120 PSI it should be ok. Really your best bet is an *old school* one, thats not electrical (i'm assuming the car one your talking about is electrical). Still, if it shows a massive drop in pressure when you operate the hydraulics its a good chance thats where your problem is at.
Its easier than swaping motors, so give it a shot!
Did you mention you had problems with your lift and tilt cylinders too? Too many posts for me to actually remember such things, i think i'm getting old! Low charge pressure could account for ALL your problems. The only problem is i'm not too sure where this is regulated.
I hope this is the problem, it saves you alot of mucking about trying to find it.
Let us know how you go.

 

[Sx200]

If your sure it is accurate and will read up to about 120 PSI it should be ok. Really your best bet is an *old school* one, thats not electrical (i'm assuming the car one your talking about is electrical). Still, if it shows a massive drop in pressure when you operate the hydraulics its a good chance thats where your problem is at.
Its easier than swaping motors, so give it a shot!
Did you mention you had problems with your lift and tilt cylinders too? Too many posts for me to actually remember such things, i think i'm getting old! Low charge pressure could account for ALL your problems. The only problem is i'm not too sure where this is regulated.
I hope this is the problem, it saves you alot of mucking about trying to find it.
Let us know how you go.

yeah the lift and tilt been playin up. and the pressure drops quite a bit and is erratic, the pressure guage is from a clear tube but only goes to 60psi, most of the tiits right round the dial lol but sometimes it drops to below 30psi. ill see if i can get another one that goes to 120psi. if it is that, how do i fix it?????

 

[Tazza]

yeah the lift and tilt been playin up. and the pressure drops quite a bit and is erratic, the pressure guage is from a clear tube but only goes to 60psi, most of the tiits right round the dial lol but sometimes it drops to below 30psi. ill see if i can get another one that goes to 120psi. if it is that, how do i fix it?????

That seems quite low....
I will try and throw a gauge on mine on the weekend to see what it shows. Its a 743 but still should give an idea of what it should be like.
I'm still not sure where the charge pressure is regulated, i'm pretty sure its done through the port block. It will be a simple spring and poppet setup, hopefully its just a worn poppet or a piece of junk stuck in the poppet. Try giving your local dealer a yell, ask where the charge pressure is regulated.

 

[skidsteer.ca]

That seems quite low....
I will try and throw a gauge on mine on the weekend to see what it shows. Its a 743 but still should give an idea of what it should be like.
I'm still not sure where the charge pressure is regulated, i'm pretty sure its done through the port block. It will be a simple spring and poppet setup, hopefully its just a worn poppet or a piece of junk stuck in the poppet. Try giving your local dealer a yell, ask where the charge pressure is regulated.

I know from haveing a pressure guage on my 553 the reading varys quite a bit. I believe 65 or so psi to be the avg.
But when driving and lifting the boom and dumping the bucket it can momentarily dip to 25 and flicket the hyd warning lite. I guess this is a result of suppling the drives and adding the oil that the hyd cylinder rods displace within the cylinder, back into the system.
Because if you lower the boom while driving and retract the tilt cylinder the pressure shoots up to @ 100 psi. But 60 to 65 seem to be the norm for just driving the machine around.
Regards Ken

 

[Sx200]

I know from haveing a pressure guage on my 553 the reading varys quite a bit. I believe 65 or so psi to be the avg.
But when driving and lifting the boom and dumping the bucket it can momentarily dip to 25 and flicket the hyd warning lite. I guess this is a result of suppling the drives and adding the oil that the hyd cylinder rods displace within the cylinder, back into the system.
Because if you lower the boom while driving and retract the tilt cylinder the pressure shoots up to @ 100 psi. But 60 to 65 seem to be the norm for just driving the machine around.
Regards Ken

ok , a bit more news, i removed the six poppets in the pump. two on one side two on the other and another two above the bottome ones? even though i dont know what to look for, one of them did looked scored around the top? is it meant to be like that? 1 took a bit of prising to get it out. i put em back in and it didnt seem to make any difference, then i went and tried to pull a tree stump out of the ground.grabbing it in the bucket and rocking back and forth. to my amazment when the stump came out the drive worked absolutley fine!!!!!!!!!!! that for a clpe of days, working hard as well...... then all of a sudden it came back, like the left drive motor is attatched to a hammer drill? was it cleaning out the poppets of the stump putting the drive under stress???? heeeelllllllpppppp its drivin me knutsssss

 

[Tazza]

ok , a bit more news, i removed the six poppets in the pump. two on one side two on the other and another two above the bottome ones? even though i dont know what to look for, one of them did looked scored around the top? is it meant to be like that? 1 took a bit of prising to get it out. i put em back in and it didnt seem to make any difference, then i went and tried to pull a tree stump out of the ground.grabbing it in the bucket and rocking back and forth. to my amazment when the stump came out the drive worked absolutley fine!!!!!!!!!!! that for a clpe of days, working hard as well...... then all of a sudden it came back, like the left drive motor is attatched to a hammer drill? was it cleaning out the poppets of the stump putting the drive under stress???? heeeelllllllpppppp its drivin me knutsssss

The wear mark you refer to, its like a full circle? if so, thats pretty much normal. Its the wear from where the poppet seats in the pump. It should still seal pretty well rite. If it did leak, it wouldn't be enough to bother things i wouldn't think. You did say it was quite tight, i'm not sure if thats normal. They should be free to move so they seal correctly.
I really have no idea what else it could be....... The knocking sound really sounds like the piston shoes snacking backwards into the yoke in the pump. It will sound and feel like a hammer drill. It still sounds like a charge pressure or replenishing valve problem. The thing that gets me is i'm sure both sides are fed through the same hole! So what affects one side, should affect the other exactly the same.
Maybee, a big maybee.... it could be the spring in the rotating group that holds it against the swash plate. This is inside the pump, so its not a small job! Like i said, a BIG maybee.
Honestly, it maybee the time to take it to the dealer to see what they think and get a pressure and flow test done. When you start pulling down a pump, if you do something wrong you will be up for BIG $$. They aren't that complicated, but you must make sure all the parts go in the rite places and around the rite way.
I can't remember if i asked before, but was the oil foamy at all? as there was a post a few days/weeks back from OLDMachinist and his 453F and his hydraulic pump. He re-kitted the pump and fixed the air problem. Air in your system could cause these problems your havig, but again, it SHOULD affect both sides the same.
If it was me, i'd go the pressure and flow test. At the least, a pressure test.
I hope you get it all sorted out!
Oh, the motor you re-built, what sort of seal was there where the shaft comes out that engages the gear box? I have a leaky motor that is slowly filling up the chain case of my 731 that i want to fix before selling it. I just don't want to go pulling the motors fully down just to replace 1 seal that can be done without pulling it to pieces. My service manual shows just a backup ring on the shaft, but there must be a seal there somewhere.

 

[Sx200]

The wear mark you refer to, its like a full circle? if so, thats pretty much normal. Its the wear from where the poppet seats in the pump. It should still seal pretty well rite. If it did leak, it wouldn't be enough to bother things i wouldn't think. You did say it was quite tight, i'm not sure if thats normal. They should be free to move so they seal correctly.
I really have no idea what else it could be....... The knocking sound really sounds like the piston shoes snacking backwards into the yoke in the pump. It will sound and feel like a hammer drill. It still sounds like a charge pressure or replenishing valve problem. The thing that gets me is i'm sure both sides are fed through the same hole! So what affects one side, should affect the other exactly the same.
Maybee, a big maybee.... it could be the spring in the rotating group that holds it against the swash plate. This is inside the pump, so its not a small job! Like i said, a BIG maybee.
Honestly, it maybee the time to take it to the dealer to see what they think and get a pressure and flow test done. When you start pulling down a pump, if you do something wrong you will be up for BIG $$. They aren't that complicated, but you must make sure all the parts go in the rite places and around the rite way.
I can't remember if i asked before, but was the oil foamy at all? as there was a post a few days/weeks back from OLDMachinist and his 453F and his hydraulic pump. He re-kitted the pump and fixed the air problem. Air in your system could cause these problems your havig, but again, it SHOULD affect both sides the same.
If it was me, i'd go the pressure and flow test. At the least, a pressure test.
I hope you get it all sorted out!
Oh, the motor you re-built, what sort of seal was there where the shaft comes out that engages the gear box? I have a leaky motor that is slowly filling up the chain case of my 731 that i want to fix before selling it. I just don't want to go pulling the motors fully down just to replace 1 seal that can be done without pulling it to pieces. My service manual shows just a backup ring on the shaft, but there must be a seal there somewhere.

thanks tazza, all the seals were available at a local seal and bearing place, 'allied seals and bearings', got high temp ones and it came to $15 for the lot.... about $150 from bobcat Australia????? i think it was just an o ring? or maybe a backup ring? no seal as such which suprised me. so it couldnt have been too hard or expensive....(id remember that lol) pulling the motor out was a painful filthy job, then gettiing the sprocket nut and sprocket off were the hardest bit. ended up getting some plumbers stilsens!! for the small nuts on the other side u need a quality 7/16 (i think) cos the holes are tight and not 6 sided.....taking the motor apart isnt that hard once its off, the timing was a bit of a bitch, couldnt work it out first time lol.................................................................................................................................................................................................................................................... as for mine sorted out air problem but didnt fix it. i just think it must have some crap lodged in somewhere. ill keep bleeding poppet and see if it clears up. asked gold coast bobcat and even though they were helpfull admitted to knowing nothin about hydraulics? which astounded me lol!!! theres a couple of other people on the coast but i got robbed over grand with the first one so am not willing to try his mate! if all else fails ill take it off (again) and have another look inside.

 

[Tazza]

thanks tazza, all the seals were available at a local seal and bearing place, 'allied seals and bearings', got high temp ones and it came to $15 for the lot.... about $150 from bobcat Australia????? i think it was just an o ring? or maybe a backup ring? no seal as such which suprised me. so it couldnt have been too hard or expensive....(id remember that lol) pulling the motor out was a painful filthy job, then gettiing the sprocket nut and sprocket off were the hardest bit. ended up getting some plumbers stilsens!! for the small nuts on the other side u need a quality 7/16 (i think) cos the holes are tight and not 6 sided.....taking the motor apart isnt that hard once its off, the timing was a bit of a bitch, couldnt work it out first time lol.................................................................................................................................................................................................................................................... as for mine sorted out air problem but didnt fix it. i just think it must have some crap lodged in somewhere. ill keep bleeding poppet and see if it clears up. asked gold coast bobcat and even though they were helpfull admitted to knowing nothin about hydraulics? which astounded me lol!!! theres a couple of other people on the coast but i got robbed over grand with the first one so am not willing to try his mate! if all else fails ill take it off (again) and have another look inside.

From what my manual tells me, there is just 1 O ring.
So to remove the motor i need to remove a gear? The manual doesn't say anything, it just shows you remove the 4 mounting bolts and pull it out. I hope to be able to just remove the shaft and install a new seal without pulling the motors down. I'm not sure how i will go, but i can only try i guess.
If the gear you are refering to is the main drive sprockets, they are indeed a total pig. The bolts are really tight and the sprocket weighs a tonne.