743 hydraulic controll valve

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jmatt20

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just picked up this machine , the valve has a broken spool. has anyone taken this valve out without taking the engine and or the pumps out? on the 843 i had the valve could be removed if you disconected the tubes and linkage and unbolted it from the case .some words not found in the bible had to be used but it could be done. anyway before i try this i'd like to know if it's possible. thanks jim
 

Tazza

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I'll let Tazza field this one, He knows his 743's inside out and upside down.
Ken
LOL Ken, so very true......
The control block “can” be removed without pulling the engine, there was a user here that did it maybe 6 months ago now. There are pictures floating around on it, i did a quick search and couldn't find it.... Either way, he left the engine in but had to pull the pumps out to gain access to the tube lines.
You say the spool is broken, can you be a little more specific? has a centering spring broken, is it leaking etc.
The only times (yes twice) i have pulled the control block out was when i was stripping a machine. Engine was out as was the hydro pump. Personally i would remove the engine (not that hard to do) and you should be able to get it out that way without too many bad words being uttered. Be sure to replace the detent balls when its out of the machine, its not fun doing it when its installed in the machine!!! it will cost no more than $2 to do.
Give me a little more info and hopefully i can steer you in the rite direction.
 

Fishfiles

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You can change the controll valve spool with out removing the controll valve from the machine , I do it all the time to change the seals , I wouldn't consider it easy but pulling the valve out completely is hard , as mentioned I'd also bet that the bolt holding the centering spring to the spool either came loose or broke , have never seen the spool break in two , but any thing is possible , if it did break there must be a reason for it , something jamming it up like when the bolts that hold the centering spring cao come out , or the ears of the cap breaking off allowing the spool to float back and forth in the bore , I have seen them bend from that , a 1/4 inch drive 3/16 allen socket and a spinner really helps this job to get out the bolts , good luck
 

Tazza

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You can change the controll valve spool with out removing the controll valve from the machine , I do it all the time to change the seals , I wouldn't consider it easy but pulling the valve out completely is hard , as mentioned I'd also bet that the bolt holding the centering spring to the spool either came loose or broke , have never seen the spool break in two , but any thing is possible , if it did break there must be a reason for it , something jamming it up like when the bolts that hold the centering spring cao come out , or the ears of the cap breaking off allowing the spool to float back and forth in the bore , I have seen them bend from that , a 1/4 inch drive 3/16 allen socket and a spinner really helps this job to get out the bolts , good luck
I need to replace the seals in my Aux hydraulic section, the problem its rite at the bottom and the 2 tube lines for the lift arms are in the way.
How much oil do you usually loose when you pull out a spool with a full tank of oil?
 

jmatt20

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I need to replace the seals in my Aux hydraulic section, the problem its rite at the bottom and the 2 tube lines for the lift arms are in the way.
How much oil do you usually loose when you pull out a spool with a full tank of oil?
i'm not sure the spool is broken. i just got the machine and i took me about four hours to get about two wheel barrows of dirt out of it. i pressure washed it and got it started,it had not run for about four years. when it started oil ran out of the third cap down on the valve . i had a friend move the controlls and could see that the cap was broken of it's ears, i assumed that the valve had broken and the pieces had pushed into the cap and broken it. my first thought was to get the valve onto the bench and take a look at it. at this point i'll get the cap the rest of the way off and take a look . fish ...you pull the spools out in the machine??? changeing those little o rings in the machine has got to be a pain ..can a broken cap alone cause the spool to slip out of place enough to cause it to leak. thanks jim
 

skidsteer.ca

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i'm not sure the spool is broken. i just got the machine and i took me about four hours to get about two wheel barrows of dirt out of it. i pressure washed it and got it started,it had not run for about four years. when it started oil ran out of the third cap down on the valve . i had a friend move the controlls and could see that the cap was broken of it's ears, i assumed that the valve had broken and the pieces had pushed into the cap and broken it. my first thought was to get the valve onto the bench and take a look at it. at this point i'll get the cap the rest of the way off and take a look . fish ...you pull the spools out in the machine??? changeing those little o rings in the machine has got to be a pain ..can a broken cap alone cause the spool to slip out of place enough to cause it to leak. thanks jim
Jim
I know on 853 the cap is what hold the seals in place between the spool and the valve. If yours is the same could definitely cause the leak. Centering spring retaining bold may have come loose and broke the cap. If the spool slides in and out freely it is likely fine. Spools don't break to often.
Does that function work ok on the loader? The leak you would have if the spool is good , just the seal is bad would be minor.
If the oil is gushing out a 10 gpm then the spool (or something major) is likely broke
Ken
 

jmatt20

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Jim
I know on 853 the cap is what hold the seals in place between the spool and the valve. If yours is the same could definitely cause the leak. Centering spring retaining bold may have come loose and broke the cap. If the spool slides in and out freely it is likely fine. Spools don't break to often.
Does that function work ok on the loader? The leak you would have if the spool is good , just the seal is bad would be minor.
If the oil is gushing out a 10 gpm then the spool (or something major) is likely broke
Ken
update... the cap had 1 ear broken off ,i removed it and saw that someone had silicon sealed the cap to the valve so i assume that this had leaked for sometime and that somenone had tried to stop the leak by sealing the cap. the spool moves in and out fine and does not appear to be broken after all. how anyone could change the seals on a spool with the valve in the machine without removeing the engine or the pumps i don't know. i took tazza advice and removed the engine ,easier than the 843 engine removal, i was making calls and scheduling jobs during the removal and it still only took about 1 1/2 hrs. if this is like the 843 valve i'm thinking that the o ring in the valve bodythat goes around the spool is the culprit. with the engine idleing this thing leaked about a quart in 10 min.
 

jmatt20

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update... the cap had 1 ear broken off ,i removed it and saw that someone had silicon sealed the cap to the valve so i assume that this had leaked for sometime and that somenone had tried to stop the leak by sealing the cap. the spool moves in and out fine and does not appear to be broken after all. how anyone could change the seals on a spool with the valve in the machine without removeing the engine or the pumps i don't know. i took tazza advice and removed the engine ,easier than the 843 engine removal, i was making calls and scheduling jobs during the removal and it still only took about 1 1/2 hrs. if this is like the 843 valve i'm thinking that the o ring in the valve bodythat goes around the spool is the culprit. with the engine idleing this thing leaked about a quart in 10 min.
on another note during removal i noticed that the bolt comeing out of the engine that the throttle linkage is attached to not only turns like it should but it wobbles back and forth like it's on a ball piviot, is that the way it should be??? the engine is a kubota and the linkage goes to a bolt on a rectangular plate mounted to the engine just aft of the injector pump. i was working the linkage to check for play when i noticed that the bolt turned and just flopped about as it turned... thank you jim
 

Fishfiles

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i'm not sure the spool is broken. i just got the machine and i took me about four hours to get about two wheel barrows of dirt out of it. i pressure washed it and got it started,it had not run for about four years. when it started oil ran out of the third cap down on the valve . i had a friend move the controlls and could see that the cap was broken of it's ears, i assumed that the valve had broken and the pieces had pushed into the cap and broken it. my first thought was to get the valve onto the bench and take a look at it. at this point i'll get the cap the rest of the way off and take a look . fish ...you pull the spools out in the machine??? changeing those little o rings in the machine has got to be a pain ..can a broken cap alone cause the spool to slip out of place enough to cause it to leak. thanks jim
Bobcat had an upgrade years back as what happened to you was a common thing back then , the original thickness of the ears of the cap where the bolts that hold it down to the valve used to be about 3/16 of an inch thick the newer caps are about 3/8 thick , it takes longer bolts with the newer style , as Tazza mentioned the cap is what holds the seal in place , so I would think you only need a cap , bolts , 2 seals (rear and front ) and I would change the rubber dirt boot on the front while you got it down , as far as getting the spool out without removing the valve it can be done , it has to be taken out from the rear , there are a couple of different configurations of the controll valve mounting and plumbing on 743's , move the tubes that are blocking removal and or unbolt the one or 2 (both) mounting bolts of the valve and move it around , it's alot of work undoing all the tubes and then getting them all back on just to change the seals , you say it's the aux , be sure as the boom cap has a detent spring and balls in it that if you pull the spool by the cap will go flying and are not easy to reinstall if you never done it before and if you find them , you may get by with just screwing in the new cap but I would have to think the seal got damaged by rubbing in and out of the bore , the black seals will go in either way but the green or cream colored seals only seals one way be sure to put the sealing side facing the valve as it will leak if you put the new seal in backwards , -------the difficult takes a while , the impossible just a little while longer ------ remember the best tool in your box is your imagination
 

skidsteer.ca

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Bobcat had an upgrade years back as what happened to you was a common thing back then , the original thickness of the ears of the cap where the bolts that hold it down to the valve used to be about 3/16 of an inch thick the newer caps are about 3/8 thick , it takes longer bolts with the newer style , as Tazza mentioned the cap is what holds the seal in place , so I would think you only need a cap , bolts , 2 seals (rear and front ) and I would change the rubber dirt boot on the front while you got it down , as far as getting the spool out without removing the valve it can be done , it has to be taken out from the rear , there are a couple of different configurations of the controll valve mounting and plumbing on 743's , move the tubes that are blocking removal and or unbolt the one or 2 (both) mounting bolts of the valve and move it around , it's alot of work undoing all the tubes and then getting them all back on just to change the seals , you say it's the aux , be sure as the boom cap has a detent spring and balls in it that if you pull the spool by the cap will go flying and are not easy to reinstall if you never done it before and if you find them , you may get by with just screwing in the new cap but I would have to think the seal got damaged by rubbing in and out of the bore , the black seals will go in either way but the green or cream colored seals only seals one way be sure to put the sealing side facing the valve as it will leak if you put the new seal in backwards , -------the difficult takes a while , the impossible just a little while longer ------ remember the best tool in your box is your imagination
The aux spool on the 743 has a detent with springs that can fly out into space too I believe
Now would be a good time to inspect the detent ball and cap for both the float on the main boom and the aux hyd lock “on”
Parts are minimal and I sure wish I'd “rebuilt” the detent on the aux hyd lock on my 553, because now I have to hold the flow on for certain attachments until I get into that miserable spot and replace the balls and cap.
Ken
 

Tazza

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The aux spool on the 743 has a detent with springs that can fly out into space too I believe
Now would be a good time to inspect the detent ball and cap for both the float on the main boom and the aux hyd lock “on”
Parts are minimal and I sure wish I'd “rebuilt” the detent on the aux hyd lock on my 553, because now I have to hold the flow on for certain attachments until I get into that miserable spot and replace the balls and cap.
Ken
I replaced my detent balls when i had the control block back in the machine... OOOH what a bitch it was..... The balls are cheap as, while you are in there, change them!. I found the easiest way was to use a cable tie and pliers. Use a few dobs of grease on the spring so the balls don't fall out and wrap a cable tie around it, set the ball to where it loops back to lock the ball in place, the other one can be a pest to keep aligned when tightening the tie. Use pliers to get it that little more tension out of it. Buy a few balls too, they find ways of flying out and getting lost!
Yes, be very careful with seal directions, the black quad rings can go on either way but if your machine uses the other pressure seals (i think my kit had green and orange ones too??), make sure the seal lips face the pressure side IE the inside of the control block and defiantly change the rubber boots. They are cheap and they will save wear on the spools. There are 2 styles of boot, one is plastic which have been replaced with rubber. If you have the old ones, remove them and the bronze spacer and install the new boot without the spacer.
Any problems just yell, i have been there before!
 

sterlclan

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I replaced my detent balls when i had the control block back in the machine... OOOH what a bitch it was..... The balls are cheap as, while you are in there, change them!. I found the easiest way was to use a cable tie and pliers. Use a few dobs of grease on the spring so the balls don't fall out and wrap a cable tie around it, set the ball to where it loops back to lock the ball in place, the other one can be a pest to keep aligned when tightening the tie. Use pliers to get it that little more tension out of it. Buy a few balls too, they find ways of flying out and getting lost!
Yes, be very careful with seal directions, the black quad rings can go on either way but if your machine uses the other pressure seals (i think my kit had green and orange ones too??), make sure the seal lips face the pressure side IE the inside of the control block and defiantly change the rubber boots. They are cheap and they will save wear on the spools. There are 2 styles of boot, one is plastic which have been replaced with rubber. If you have the old ones, remove them and the bronze spacer and install the new boot without the spacer.
Any problems just yell, i have been there before!
Tazza put a shop vac on the filler no filter in the vac turn the vac on and remove whatever you need to no fluid will leak I just did this on the mack tractor at work it holds about 25 gallons had to changt the pump lost about two quarts that was in the line be sure you have all the parts you need as the shop vac wont like it much Jeff
 

Tazza

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Tazza put a shop vac on the filler no filter in the vac turn the vac on and remove whatever you need to no fluid will leak I just did this on the mack tractor at work it holds about 25 gallons had to changt the pump lost about two quarts that was in the line be sure you have all the parts you need as the shop vac wont like it much Jeff
Thats a neat idea! I'll do that when i get motivated and replace my seals.
As for the linkage, the bolt should not turn, it should be a flexible linkage though that allows it to self align but the part that bolts on to the throttle arm should be tight.
I agree, the oil will be leaking out the quad ring that seals between the body of the control block and the spool. Be very easy when re-installing the Quad ring, they are easy to catch on the sharp edges on the spool or the block that will damage the seal. Use lots of oil and be gentle, you will be fine!
As stated earlier, the only way to remove the spool is out the back, do not remove the bolt that holds the spring unless the spring was broken, the bolt is loctited it and must be heated, just warning you so you won't try and remove the spring and replace the seal with the spool in place still. I wish i could do it this way as mine leaks out the back only.
 

skidboy

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Thats a neat idea! I'll do that when i get motivated and replace my seals.
As for the linkage, the bolt should not turn, it should be a flexible linkage though that allows it to self align but the part that bolts on to the throttle arm should be tight.
I agree, the oil will be leaking out the quad ring that seals between the body of the control block and the spool. Be very easy when re-installing the Quad ring, they are easy to catch on the sharp edges on the spool or the block that will damage the seal. Use lots of oil and be gentle, you will be fine!
As stated earlier, the only way to remove the spool is out the back, do not remove the bolt that holds the spring unless the spring was broken, the bolt is loctited it and must be heated, just warning you so you won't try and remove the spring and replace the seal with the spool in place still. I wish i could do it this way as mine leaks out the back only.
You can replace the seals without removing the spool, i do it often but you need a special tool to install the balls on the lift and aux.spools.Other two spools are not a problem.
 

Tazza

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You can replace the seals without removing the spool, i do it often but you need a special tool to install the balls on the lift and aux.spools.Other two spools are not a problem.
How do you replace the seals without pulling the spool out? I need to replace mine again and i'd like to not pull the spool if possible. The only way i can see is to remove the spring on the back which my manual says not to touch. Replacing the detent balls sure is a bitch to do!
 

skidboy

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How do you replace the seals without pulling the spool out? I need to replace mine again and i'd like to not pull the spool if possible. The only way i can see is to remove the spring on the back which my manual says not to touch. Replacing the detent balls sure is a bitch to do!
All you need todo is undo the end cap (leave the C clip and washer attached ) Pull the end cap off slowly and the 2 balls and spring will still be captive in the cap.Use a 3/16 allan key and undo the spring retainer.Hold some pressure on the retainer so it doesnt hit you in the gob.Take the spring,washer etc off.Use a pick and remove the old seal (be careful not to scratch the sealing area of either the spool or housing.The only trickey bit is replacing the outer set of ball and spring.Bobcat use to sell a special tool (its C shaped and it fits over the hole in the spring retainer.You feed a ball,spring,ball through a hole in the tool,fit a screw in to the tool ,which compresses the balls together and you simply push the inner cap over thspring retainer.It sounds complicated but its about a 20 min. job in total, and no loss of oil.
 

Tazza

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All you need todo is undo the end cap (leave the C clip and washer attached ) Pull the end cap off slowly and the 2 balls and spring will still be captive in the cap.Use a 3/16 allan key and undo the spring retainer.Hold some pressure on the retainer so it doesnt hit you in the gob.Take the spring,washer etc off.Use a pick and remove the old seal (be careful not to scratch the sealing area of either the spool or housing.The only trickey bit is replacing the outer set of ball and spring.Bobcat use to sell a special tool (its C shaped and it fits over the hole in the spring retainer.You feed a ball,spring,ball through a hole in the tool,fit a screw in to the tool ,which compresses the balls together and you simply push the inner cap over thspring retainer.It sounds complicated but its about a 20 min. job in total, and no loss of oil.
Well that sounds easy enough! I was just worried that they said not to remove the centering spring as i guess the bolt is secured with loctite. Only my rear aux seal is leaking on the rear side, so doing it this way makes life a lot easier for me!
As for the detent ball installation tool, i have a design in my head that may work, i may have a stab at building one. The C shape you speak of sounds simple enough to build, we shall see if i can build something that will do the job.
 

skidboy

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Well that sounds easy enough! I was just worried that they said not to remove the centering spring as i guess the bolt is secured with loctite. Only my rear aux seal is leaking on the rear side, so doing it this way makes life a lot easier for me!
As for the detent ball installation tool, i have a design in my head that may work, i may have a stab at building one. The C shape you speak of sounds simple enough to build, we shall see if i can build something that will do the job.
The bolt you talk about is actually a stud and stays in the spool when you undo the spring retainer.The other end of the spring is a locating washer,make sure on assembly that when doing up the spring retainer that the washer is centred so that the spigot on the spring retainer goes through the washer and tightens up on the spool.It will make sense when you get it apart and look at it.
 
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