743 controll valve spool seals

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Fishfiles

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I got to do controll valve seals on a 743 next week , I done this job many times but it has been quite a few years since I did it -------------- hoping to get a refresher course on the job , pretty sure I can pull the spools without pulling the valve , but seem to remember some variations of the machine were harder than others , remember using a long extension on a 1/4 " ratchet with a allen socket to undo the rear caps , but can't remember the front caps too well ------------ can any one walk me thru whats got to be moved to get to the front and how many hours should I figure so I can better plan my day
 

skidsteer.ca

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I just did a later 743 (not b series though)
It had a 4 spool (yes 4 ) monoblock valve, (Some had a greasen segmented valve) and was told the one I had was easier.
I had to remove the suction line from the pump, a smaller valve bolted to the side of the machine. The side cover between the tires. Then I could just get my hand in there to unhook the linkages and remove the boots around the spools.
You can leave the detents all assembled and slide the spool out the back with all the caps on it so as to not disturb the detent, once you get the caps screws out. You wil need a lot of extensions to reach these.
Ken
 

Tazza

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I just did a later 743 (not b series though)
It had a 4 spool (yes 4 ) monoblock valve, (Some had a greasen segmented valve) and was told the one I had was easier.
I had to remove the suction line from the pump, a smaller valve bolted to the side of the machine. The side cover between the tires. Then I could just get my hand in there to unhook the linkages and remove the boots around the spools.
You can leave the detents all assembled and slide the spool out the back with all the caps on it so as to not disturb the detent, once you get the caps screws out. You wil need a lot of extensions to reach these.
Ken
The allen head extension really is needed for the front boot covers too.
The only issue i had was one segment was a little tight with the tube line for the lift rams. These can be slightly bent if needed.
I guess the only thing i can really add is to pump as much fluid out as you can into a drum then work. As the oil reserve is higher tahn the valve, it will slowly, or not so slowly pour out.
 

7LBSSMALLIE

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The allen head extension really is needed for the front boot covers too.
The only issue i had was one segment was a little tight with the tube line for the lift rams. These can be slightly bent if needed.
I guess the only thing i can really add is to pump as much fluid out as you can into a drum then work. As the oil reserve is higher tahn the valve, it will slowly, or not so slowly pour out.
743 valves aint fun never have been never will. parts ident can be an issue as well. mod and s/n wont do it need valve ident. seals have been changed so many times its best to have old in hand.. another thought is for ease of access you can have eng out in a hr, allowing you inspect u joint ,tubelines that run under,and stat input shaft seal. but can be done in unit ,just a pain not as bad as pulling valve wich something you do not wantt to do.
 
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Fishfiles

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It took 3 hours and 15 minutes of work time to change the seals on 4 spools , I was guessing 4 hours , it had a 4 spool valve and one spool wan't being used but changed the seals on it any way as I had a complete kit , the job was hard because of rust , the clevis pins on the linkage to the boom valve spool were frozen up pretty good , thank goodness for the Kroil , the arm that goes under the pump from the left pedal gets right in the way of things , taking out the flow divider gave some room , and took off two tubes and 3 hoses , in the rear the bottom spool to the aux was blocked by a steel tube but really wasn't too bad to get out the tube loose and out the way , the hardest problem was one I could have never guessed , one of the seal holders was rusted in and took a lot of time , Kroil and tapping to get it to come off , the machine was filthy and pressure washing first would have been great , 1/4 " air ratchet with the 1/4" drive 3/16" allen socket with about 3 foot of extension for the rear and 3 inches for the front is the key to save a lot of time on this job ------------------in the kit was a very small oring and a white plastic needle valve looking part , have no clue to where it goes
 

Tazza

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It took 3 hours and 15 minutes of work time to change the seals on 4 spools , I was guessing 4 hours , it had a 4 spool valve and one spool wan't being used but changed the seals on it any way as I had a complete kit , the job was hard because of rust , the clevis pins on the linkage to the boom valve spool were frozen up pretty good , thank goodness for the Kroil , the arm that goes under the pump from the left pedal gets right in the way of things , taking out the flow divider gave some room , and took off two tubes and 3 hoses , in the rear the bottom spool to the aux was blocked by a steel tube but really wasn't too bad to get out the tube loose and out the way , the hardest problem was one I could have never guessed , one of the seal holders was rusted in and took a lot of time , Kroil and tapping to get it to come off , the machine was filthy and pressure washing first would have been great , 1/4 " air ratchet with the 1/4" drive 3/16" allen socket with about 3 foot of extension for the rear and 3 inches for the front is the key to save a lot of time on this job ------------------in the kit was a very small oring and a white plastic needle valve looking part , have no clue to where it goes
It is used if you remove the spring from the spool. Its down pretty deep, if you didn't touch the springs, don't worry about it!
The main seals to replace were the black quad rings at either end of the spools.
 

mac5367

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It is used if you remove the spring from the spool. Its down pretty deep, if you didn't touch the springs, don't worry about it!
The main seals to replace were the black quad rings at either end of the spools.
Does any one know where the best place is to get the valve spool seal kits? Part number 6816251. I called the bobcat dealer but I think they are ripping me off for one spool kit is $30. Thanks, Mike
 

Tazza

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Does any one know where the best place is to get the valve spool seal kits? Part number 6816251. I called the bobcat dealer but I think they are ripping me off for one spool kit is $30. Thanks, Mike
That is about the go.
You can always take the seals to a hydraulic seal shop to get them matched, it is your choice if you go that way or not. The quad rings used are quite cheap, but the kit from the dealer you know is right.
 

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