853, hydrostatic pump leaks on top, easy to fix??

[thetool]

Okay-you don't have to pull your pump out and down to fix it.
If you remove the cable by removing the nuts and bolts at the lever, and the bracket bolts on the servo cover, you swing the cable out of the way, and you're ready to proceed.
You really need to dump the oil or it will drain the tank.
Clean off the top and mark the v-notch on the bracket, remove the sector adustment bolt and pull the assembly straight out. This will be the spool, the adjustment bracket, a clothespin-type spring and the lever all held together with a nut on top of the spool. There's an 0-ring and a white teflon back-up ring on the spool. If the spring is broken, as they commonly are, you have to disassemble this assembly to replace it, so you have to note the orientation of the spool to the bracket, because it has weird metering notches cut into it and it's not symmetrical.
Now your sleeve is still in the bore of the pump, and it's tough to pull out. It sticks up out of the pump about 1/4". Around this sleeve is where it commonly leaks. Dirt gets in the bore around the sleeve and takes out the o-ring and back-up ring(same as the spool, but larger diameter) AND puts a groove in the bore of the pump housing, which makes it almost impossible to repair by replacing the o-ring.
So for big bucks, but far less than the cost of a new pump, Bobcat offers replacement sleeves that have an o-ring groove further down on the sleeve from the top, so your new o-ring has a new, ungrooved contact surface, along with some protection washers to keep the dirt out in the future.
To pull the sleeve, I get a pair of vise grips, adjusted tight enough that it won't slip on the sleeve, but not so tight that it marks it. Clamp the vise-grip onto the sleeve, vise-grip horizontal, and use a pry-bar under the jaws of the vise-grip, between the jaws and the top of the pump, hold down with my hand on the vise grip handle and gently pry the sleeve straight up and out.
New sleeve or old, it has a notch cut out of the bottom of the sleeve. This notch indexes on a pin down inside the pump, and if you don't line it up squarely, it won't go in. The notch faces the servo when it goes in, and has to be exactly perpendicular to the long axis of the pump to catch the pin.
The sleeve will go down and stop short. This is where guys get impatient and tap it with a hammer and shear that little pin down in there. DON'T DOO DAT!.....=).
If everything's lined up, it will go down with hand pressure only. Both thumbs pushing down and it will pop in.
If you pay attention to your spool orientation, don't use a hammer or any other tapping or pounding device, don't mess with the cable lengths, line the notch on the bracket and get it back together in the same place, you shouldn't have any problems.
The parts breakdown list has all the parts you need, but there is more detail in the service letter I mentioned, more detail that in the service manual. Often the dust washers are neglected, I think they're important. Those sleeves are about $300 each and I think bobcat quotes the pump at $6K, 'cause it's no longer in production.
I also like to double o-ring instead of the back-up washer on the sleeve. Sometimes this will get you by without the updated sleeve, but get the dust washers regardless.
It sounds more complicated than it really is, and I'm sure you can do it.

I just re-read, and this is wrong:
"The notch faces the servo when it goes in, and has to be exactly perpendicular to the long axis of the pump to catch the pin."
Actually the servo is perpendicular to the long axis of the pump. The notch goes in exactly squarely facing the center of the servo, so the notch is PARALLEL to the long axis of the pump.
I hope you're not confused by this.......=).

 

[Muddin_Mavric]

I just re-read, and this is wrong:
"The notch faces the servo when it goes in, and has to be exactly perpendicular to the long axis of the pump to catch the pin."
Actually the servo is perpendicular to the long axis of the pump. The notch goes in exactly squarely facing the center of the servo, so the notch is PARALLEL to the long axis of the pump.
I hope you're not confused by this.......=).

thanks a ton those are some really great step by step instructions. i will wait till spring to try it once its done snowing so if i have to leave it site torn aprat while i order parts snow wont stack up all over.
since you seem to know alot about this pump i have one more question. do you know what the "centering screw" and the "neutral adjustment lock nut" are for. they are on the pump and i see them mentioned in the service manual.

 

[thetool]

thanks a ton those are some really great step by step instructions. i will wait till spring to try it once its done snowing so if i have to leave it site torn aprat while i order parts snow wont stack up all over.
since you seem to know alot about this pump i have one more question. do you know what the "centering screw" and the "neutral adjustment lock nut" are for. they are on the pump and i see them mentioned in the service manual.

Yes, you can see them in your picture. On the front of the servo, right in the center, a locknut surrounding a socket-head (hex or 'allen') screw.
It's somethng that is not normally messed with, unless you take your pump ALL the way down, or it gets really out of whack.

 

[thetool]

Yes, you can see them in your picture. On the front of the servo, right in the center, a locknut surrounding a socket-head (hex or 'allen') screw.
It's somethng that is not normally messed with, unless you take your pump ALL the way down, or it gets really out of whack.

Again, I failed to answer your question, I thought you asked where they are......=).
There's a piston inside that servo cylinder, that is attached to your swashplate in the pump. When the pump control is in neutral, oil pressure on each side of that servo piston is equal, and the piston, along with the swash plate attached to it, is centered. The adjustment screw and locknut adjusts spring tension inside the servo, against the piston, to center the piston when in neutral.
It is not a shortcut to setting the nuetral on the machine, however, because you still have linkage and cables and control spools in the mix and any tweaking of that screw throws everything else off.

 

[Muddin_Mavric]

Again, I failed to answer your question, I thought you asked where they are......=).
There's a piston inside that servo cylinder, that is attached to your swashplate in the pump. When the pump control is in neutral, oil pressure on each side of that servo piston is equal, and the piston, along with the swash plate attached to it, is centered. The adjustment screw and locknut adjusts spring tension inside the servo, against the piston, to center the piston when in neutral.
It is not a shortcut to setting the nuetral on the machine, however, because you still have linkage and cables and control spools in the mix and any tweaking of that screw throws everything else off.

hey thetool,

thanks for the great explanation. i think im the worlds best procrastinator but i finally got to fixing that leak, eeerrrrr, well trying to fix that leak. i had a slight problem. the control sleeve would not come out so i kept clamping harder and harder with the vise grips. well all of a sudden, POP!!!! it cracked in 2 spots looks like i will be getting the updated sleeve now. i did finally get it out though. and then those morons at the bobcat dealer gave me the o-ring and backup ring for the spool not the sleeve! unless i go in there with a part number they find a way to mess up!

the one question i have is how am i going to get the new control sleeve in there with out a hammer if the old one came out that hard?? i stuck my finger in there and i can feel the pin on the same side as the pully for the pump. and it also feels like there is a slight vertical grove on the same side as the pin in the bore that the sleeve came out of. is that going to be a problem with the new sleeve??

 

[thetool]

hey thetool,

thanks for the great explanation. i think im the worlds best procrastinator but i finally got to fixing that leak, eeerrrrr, well trying to fix that leak. i had a slight problem. the control sleeve would not come out so i kept clamping harder and harder with the vise grips. well all of a sudden, POP!!!! it cracked in 2 spots looks like i will be getting the updated sleeve now. i did finally get it out though. and then those morons at the bobcat dealer gave me the o-ring and backup ring for the spool not the sleeve! unless i go in there with a part number they find a way to mess up!

the one question i have is how am i going to get the new control sleeve in there with out a hammer if the old one came out that hard?? i stuck my finger in there and i can feel the pin on the same side as the pully for the pump. and it also feels like there is a slight vertical grove on the same side as the pin in the bore that the sleeve came out of. is that going to be a problem with the new sleeve??

I'm upset that you broke your sleeve......=(. How did you get it all out? I don't understand how you can get your finger down in that hole far enough to feel the pin, but I'll take your word for it.....I can't see the machine. The pin should be on the same side as the servo, or the crossways cylinder part of the pump.
It must have had a lot of dirt or whatever inside, maybe a torn and jammed up o-ring and/or back-up ring. If everything is right, you should be able to pop in the new sleeve with nothing but firm hand pressure only.
I don't recall ever being able to feel any vertical groove. I dunno, maybe I just have real fat fingers.....=).
The notch in the bottom of the sleeve slides over the pin in the bore. That pin is a very delicate and shallowly set spring pin and it is easy to shear or knock out of place. You will have to pull your engine and pump to fix that!
Let me know what they want for two new sleeves. I found a pair of the updated ones im ym toolbox the other day.
I will try and find the diagrams for this fix later, and get back within a couple days on this thread. I'm sorry you're having troubles with it.

 

[Muddin_Mavric]

I'm upset that you broke your sleeve......=(. How did you get it all out? I don't understand how you can get your finger down in that hole far enough to feel the pin, but I'll take your word for it.....I can't see the machine. The pin should be on the same side as the servo, or the crossways cylinder part of the pump.
It must have had a lot of dirt or whatever inside, maybe a torn and jammed up o-ring and/or back-up ring. If everything is right, you should be able to pop in the new sleeve with nothing but firm hand pressure only.
I don't recall ever being able to feel any vertical groove. I dunno, maybe I just have real fat fingers.....=).
The notch in the bottom of the sleeve slides over the pin in the bore. That pin is a very delicate and shallowly set spring pin and it is easy to shear or knock out of place. You will have to pull your engine and pump to fix that!
Let me know what they want for two new sleeves. I found a pair of the updated ones im ym toolbox the other day.
I will try and find the diagrams for this fix later, and get back within a couple days on this thread. I'm sorry you're having troubles with it.

the sleeve didnt really break it just cracked in 2 spots 180 deg. apart. the cracks are about 1" long. once it cracked i turned the vise grips up all the way and the only way it would move is to turn the sleeve just a bit back and forth as i pryed up. it didnt crack untill it was half way out and really started to hang up. the one oring on there was in pretty tough shape. i can see why it leaked.
i can feel what i asume is the pin if i stick my little finger all the way in the hole as far as i can get it. to me the vertical grove feels like a scratch/gouge which is why im worried about the new one going in. that sleeve has to be able to turn freely once its all the way in right? or does that pin hold it so it cant really move at all? they told me $205.87 for the sleeve. and thats going by the part number in the service bullitan so it should be right. plus i will have to buy the right o-rings that they should have sold me to begin with.

thanks again for all the help.

Justn Behr

 

[Tazza]

the sleeve didnt really break it just cracked in 2 spots 180 deg. apart. the cracks are about 1" long. once it cracked i turned the vise grips up all the way and the only way it would move is to turn the sleeve just a bit back and forth as i pryed up. it didnt crack untill it was half way out and really started to hang up. the one oring on there was in pretty tough shape. i can see why it leaked.
i can feel what i asume is the pin if i stick my little finger all the way in the hole as far as i can get it. to me the vertical grove feels like a scratch/gouge which is why im worried about the new one going in. that sleeve has to be able to turn freely once its all the way in right? or does that pin hold it so it cant really move at all? they told me $205.87 for the sleeve. and thats going by the part number in the service bullitan so it should be right. plus i will have to buy the right o-rings that they should have sold me to begin with.

thanks again for all the help.

Justn Behr

Thats an awful lot for a sleeve.... But its one of those things you need i guess. As long as you fix your leak, that's all that matters!

 

[Muddin_Mavric]

Thats an awful lot for a sleeve.... But its one of those things you need i guess. As long as you fix your leak, that's all that matters!

yeah i know. im a machinist by trade and thought about trying to make it my self but it looks like its chrome plated and maybe ground. we dont have a cylindrical grinder so i cant grind it or an EDM machine for the square hole.
the leak was getting pretty bad. in 2 weeks time i put on about 12 hours and my hud. fluid went from full to the add mark. it leaks worse when its running but even just sitting there it leaks. for all i know there might be more leaks but with the mess this ones making its kinda hard to tell.

 

[thetool]

yeah i know. im a machinist by trade and thought about trying to make it my self but it looks like its chrome plated and maybe ground. we dont have a cylindrical grinder so i cant grind it or an EDM machine for the square hole.
the leak was getting pretty bad. in 2 weeks time i put on about 12 hours and my hud. fluid went from full to the add mark. it leaks worse when its running but even just sitting there it leaks. for all i know there might be more leaks but with the mess this ones making its kinda hard to tell.

I'll let you have both my new sleeves for less than the cost of one.....=). I was holding them to sell locally for $100 each. Let me know.
Anyway, don't use the back-up washer on the sleeve, but rather two o-rings. Make sure to get the little washers that cover the assembly to keep dirt out.
The sleeve actually does rotate slightly in the bore in use. It follows the metering spool slightly and the groove on the bottom of the sleeve actually moves the servo control, which moves the piston, which moves the swash. Power steering. Are you sure that vertical groove is not a machined notch rather than a wear groove? With your new sleeve, remove the o-rings, clean with some oil, do the old in-and-out test, slow and careful, to make sure it dosen't hang up. This will aslo help you with the correct orientation, when you install it with the o-rings, they are what cause it to "pop" in and they engage the bore at the same time the notch down low engages the pin, which is why it is so easy to screw up if you ain't careful.
I really wish I was there to help you out with this, but I know you can do it....=).

 

[Muddin_Mavric]

I'll let you have both my new sleeves for less than the cost of one.....=). I was holding them to sell locally for $100 each. Let me know.
Anyway, don't use the back-up washer on the sleeve, but rather two o-rings. Make sure to get the little washers that cover the assembly to keep dirt out.
The sleeve actually does rotate slightly in the bore in use. It follows the metering spool slightly and the groove on the bottom of the sleeve actually moves the servo control, which moves the piston, which moves the swash. Power steering. Are you sure that vertical groove is not a machined notch rather than a wear groove? With your new sleeve, remove the o-rings, clean with some oil, do the old in-and-out test, slow and careful, to make sure it dosen't hang up. This will aslo help you with the correct orientation, when you install it with the o-rings, they are what cause it to "pop" in and they engage the bore at the same time the notch down low engages the pin, which is why it is so easy to screw up if you ain't careful.
I really wish I was there to help you out with this, but I know you can do it....=).

hey thanks for the offer but i just ordered the new updated one today from bobcat. usually it gets here in 2 days. so i think i will be able to get it back together this weekend. i tried to slide the old one in up to the first o-ring grove and i had a heck of a time getting it to go in. maybe the new one will slide in better.

 

[Muddin_Mavric]

hey thanks for the offer but i just ordered the new updated one today from bobcat. usually it gets here in 2 days. so i think i will be able to get it back together this weekend. i tried to slide the old one in up to the first o-ring grove and i had a heck of a time getting it to go in. maybe the new one will slide in better.

just one more question. lets say that there is a scratch in there with a bit of raised material that is keeping the sleeve from sliding in, what would you recomend to fix it so that i can get the sleeve in? i tried putting the old sleeve in the freezer and getting it to go in with out any o-rings on it and it would not go in more than about 3/16 of an inch. could i try to lightly hone it? if any small metal particals would get in my pump from honing it would that totally wreck it?

 

[thetool]

just one more question. lets say that there is a scratch in there with a bit of raised material that is keeping the sleeve from sliding in, what would you recomend to fix it so that i can get the sleeve in? i tried putting the old sleeve in the freezer and getting it to go in with out any o-rings on it and it would not go in more than about 3/16 of an inch. could i try to lightly hone it? if any small metal particals would get in my pump from honing it would that totally wreck it?

This is beyond my experience. I am stumped as to why there is a hangup. I imagine if you could somehow get something in there and buff out the burr, you could leave it open, pour some oil in the inlet or tank and let gravity wash it out, coming up through the bore. Like it would if you removed the spool with the tank full.
I'm wondering what the control is going to be like even if you get the burr smoothed out, with some kind of gouge in that bore.
Other than that, you may be looking at a pump teardown. This is a head-scratcher for me, maybe somebody else will chime in with a better idea.
Sorry man....not much help. Best I can do without looking at it.......=(.

 

[Muddin_Mavric]

This is beyond my experience. I am stumped as to why there is a hangup. I imagine if you could somehow get something in there and buff out the burr, you could leave it open, pour some oil in the inlet or tank and let gravity wash it out, coming up through the bore. Like it would if you removed the spool with the tank full.
I'm wondering what the control is going to be like even if you get the burr smoothed out, with some kind of gouge in that bore.
Other than that, you may be looking at a pump teardown. This is a head-scratcher for me, maybe somebody else will chime in with a better idea.
Sorry man....not much help. Best I can do without looking at it.......=(.

thanks again for all the advice i couldn't have dont it with out you. im kinda ticket because the sleeve that i ordered is the exact same as the one that was in there. i gave them the part number from the service builitain and they said that part no longer existed but there was an updated one instead that they sent me. the o-ring was in the same spot. some how that new sleeve went right in when the old one would not. it went in over 1/2" with out me even pushing on it. i had to push on it with every thing i had. then once it was in i was also able to pull it back out with just a pliers to see where the holes were to get that notch lined up with the pin. i guess i dont understand why the old one was so tight and this one slides in and out without any problems.
its seems to steer just fine, well as good as can be expected for a 853. i ran it for about 1.5 hours last night and from what i can see from the back door it looks like the leak has stoped. before i could see a steady stream running down the backside of the pump. i also put an extra o-ring around the top of the sleeve like it shows in the service builitan even though it just sits on that bore and not in a grove. and of corse the dust washer.

 

[thetool]

thanks again for all the advice i couldn't have dont it with out you. im kinda ticket because the sleeve that i ordered is the exact same as the one that was in there. i gave them the part number from the service builitain and they said that part no longer existed but there was an updated one instead that they sent me. the o-ring was in the same spot. some how that new sleeve went right in when the old one would not. it went in over 1/2" with out me even pushing on it. i had to push on it with every thing i had. then once it was in i was also able to pull it back out with just a pliers to see where the holes were to get that notch lined up with the pin. i guess i dont understand why the old one was so tight and this one slides in and out without any problems.
its seems to steer just fine, well as good as can be expected for a 853. i ran it for about 1.5 hours last night and from what i can see from the back door it looks like the leak has stoped. before i could see a steady stream running down the backside of the pump. i also put an extra o-ring around the top of the sleeve like it shows in the service builitan even though it just sits on that bore and not in a grove. and of corse the dust washer.

I'm glad it runs and good job on the fix!
Thank you for getting back and letting us know how it went and what it took, we all learn that way....=).

 

[FJRDarksider]

This is an old thread but appears to be what I am looking for. My 1993 853 has a slight leak on the right side, but more troubling, is that the lever won't allow full swing on the steering for forward motion. Reverse is fine (and the left side steering movement is fine), but it won't move all the way for forward movement on the right side (I have to hold back the left side steering lever to prevent it from always turning right). As such, I don't get the full speed in forward.
Something seems to be stopping it. Its not the cable action as it definitely has room and "wants" to pull it forward but something is preventing that. I did notice the clothespin type spring is broken on that side.
I am hoping this is an external issue, but is there something internal in the servo that could cause this?