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Thread: Replacing Bobcat loader control valve seals

  1. #1
    Super Moderator willie59's Avatar
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    Replacing Bobcat loader control valve seals

    Occasionally a member finds their Bobcat loader control valve making an oily mess of the bottom of their machine because it needs new seals for the control valve spools. Some simply take the machine to their local Bobcat dealer for repair, but others consider doing the repair themselves and save a little money, to which they ask if this is a job that they can do. If one has a bit of mechanical skills, it certainly is a project that can be done. Here are the basic steps to accomplish the repair. This was done on a 773 G Series loader. There may be differences on older models, such as a 743, but the differences have little affect on the procedures for doing this repair. On the wheel loaders, it's a little easier because you can remove a side plate to access the front of the control valve easy. On the track machines, such as T190, the track frame gets in the way of working through side panel so all parts of the repair are done on the topside with cab raised. Worst part about doing this repair is the stuff in the way of accessing the control valve components, but that just comes with working on a Bobcat, pretty much everything you need to work on with these machines has something in your way. Sorry about a few fuzzy pics, I had to get in a few awkward positions to take pics and it was hard to hold camera still while flash working. So, lets re-seal a control valve. If your working on a wheel machine, take the time to clean out the debris and gunk from underneath the drive motor on the control valve side by reaching through the removed side plate hole between wheels. At the rear of that compartment is a hole in the belly of the machine. Place an oil drain pan under the hole to contain the oil that will drain from control valve while making repairs. Track machines have the hole in a different location.

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    Last edited by willie59; 05-31-2010 at 11:38 AM.
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  2. #2
    Super Moderator willie59's Avatar
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    Remove the linkage pins where the foot pedals links connect to the valve spools. Notice that rectangular link on the bottom spool, note it has two holes in the front of it where the traverse arm from the left pedal connects to it. Note which hole your traverse arm pin is in. Otherwise, when you reassemble the machine, you'll be scratching your head which hole it was in.

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    Remove the bolt that connects the right foot pedal to the linkage arm. Pull the linkage arm forward toward front of machine.

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    Remove the center pivot retainer bolt and washer from the traverse arm from left pedal, remove the two pivot mount nuts on each side of the center pivot, pull the traverse arm free and forward.

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  3. #3
    Super Moderator willie59's Avatar
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    Now with the links pulled forward away from control valve you have need room to work on the control valve. Remove the four allen head bolts that secure the rubber spool dust boots and the spool lock assembly.

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    Remove the rubber dust boots from the two spools. Now, with seat bar down, turn on ignition switch (or Run button if keypad control) but do not start engine. Push green Operate button at left control console. This will activate spool lock solenoids. Now simply slide spool lock assembly forward and off of valve spools. Once free of spools, turn ignition off. No need to disconnect wires, simply place lock assembly out of the way.

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    Notice, for reassembly, that the coil on the end goes up, the backside of the lock assembly is smooth, and the front has a depression for the dust boots to
    fit in.

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    Slide the seal retainer disks foward and off the spools, and remove o-ring seals that sealed the mounting of spool lock assy to valve body.

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    Now it's time work topside under raised cab on the backside of the valve body. You may have plastic seal caps on the spool centering spring caps. You can leave the plastic cap in place on top spool spring cap (green cap in pic below), but remove the bottom one to access the e-clip on the back of the lower spool cap. Very important, remove the e-clip and washer. If you don't, your likely to have 2 detent balls and a spring go to meet Alice in Wonderland in the belly of the machine when you remove the centering spring cap. Don't ask me how I know that.

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    Last edited by willie59; 05-31-2010 at 11:35 AM.
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  4. #4
    Super Moderator willie59's Avatar
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    Remove the 2 allen head screws that secure the top spool cap and remove cap.

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    Remove the 2 allen head screws that secure the lower spool cap. Grasp the cap and gently pull it off the detent mechanism. Make certaing that shaft sticking out the back of the cap is loose and free as your removing the cap. Do not put any pull on that shaft.

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    Grasp the centering spring of the lower spool. Do not grasp or disturb the detent mechanism on the rear of the spool. Gently pull the entire spool assembly backwards out of the valve body.


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    Remove the top spool assembly in same manner by grasping centering spring and pull entire spool out of valve body. Here are the two spool assemblies with old seals and seal retainer disks still on the spools.


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    Now go back to front side of valve body and remove the old spool seals that are still in the valve body bores. Make sure there are no fragments of old seals left in the front or rear bores of valve body.

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    Last edited by willie59; 05-31-2010 at 11:39 AM.
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  5. #5
    Super Moderator willie59's Avatar
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    Here's the 4 new spool seals and 2 o-rings to seal the spool lock assembly mounting.

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    Notice the lip on the outer part of seal. The lip goes inward in the valve bores.

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    Clean the valve spool with starting fluid or brake cleaner and compressed air to insure there's no dirt/grit on spool, place spools on a clean cloth while working with them. Lubricate the valve spool, then gently slip a new seal onto the spool, working it to the centering spring end of the spool. Take your time and be patient, being careful as your working the seal over the sharp edges along the spool.

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    Here's the two spools with new seals fitted.

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    Last edited by willie59; 05-31-2010 at 12:18 PM.
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  6. #6
    Super Moderator willie59's Avatar
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    Inspect the front and backside of the valve body to make sure there is no dirt/grit, clean if necessary. Make certain no dirt/grit gets in valve body bores or areas where seals go. Lubricate the lower spool with detent mechanism with assembly grease, place some grease where the seal will fit into valve body bore. Slide the spool into the lower valve bore until seal reaches valve body.

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    Once seal encounters face of valve body, place fingers at rear of spool. Push the spool in with firm/steady finger pressure, the seal will pop into place in valve body. Perform same procedure for upper spool.

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    Re-install the centering spring caps. Fit the washer and e-clip on detent device shaft. Re-fit plastic protector cap over e-clip.

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    Last edited by willie59; 05-31-2010 at 12:18 PM.
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  7. #7
    Super Moderator willie59's Avatar
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    Go back to front of valve body, lubricate spools with assembly grease, gently fit new seals on spools. Make sure outer lip on seal goes inward toward valve body. Slip seal retainer disks on spools.

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    Using steady finger pressure, press seal retainer disks inward to pop seal home in valve body.

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    Apply a good amount of assembly grease to groove around outside perimeter of seal retainer disks on top and bottom spool. Fit your 2 new o-rings in the grooves around the seal retainer disks, pressing them fully into the grease in grooves. Smear the grease around the face of the o-rings. The grease will hold the o-rings in place during installation of spool lock assembly. (Sorry, my pic of o-rings installed was no good)


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    Thoroughly clean the spool lock assembly with starting fluid or brake cleaner, dry with compressed air. Apply a film of assembly grease to the bores of the lock assy. Turn ignition on and press operate button to activate spool lock solenoids. Gently slide lock assy onto spools and home against valve body.

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    Make certain you don't disturb seal lock assy after it's planted against valve body or you could upset one of the o-rings and get this. It appears whoever was in this valve before didn't properly set o-ring, this is what will result, tearing of the o-ring.

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    Super Moderator willie59's Avatar
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    Apply some assembly grease to end of spools and spool lock assembly.

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    Fit rubber dust boots onto spools. Replace boots if cracked or deteriorated. Install allen head mounting screws. Tighten each screw a little at a time to evenly set pressure on o-ring seals. Don't just lock one screw down and move to the next. Once allen head screws are set, turn iginition off.

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    Rotate the top spool so the flats on spool are vertical, rotate the bottom spool so flats are horizontal. Go to front of cab, slide linkage bar backwards at right pedal, fit linkage to pedal with mounting bolt but do not tighten bolt yet.

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    Re-install the traverse bar from left pedal onto pivot at center of traverse bar. Now you can re-install the link connections to spools. If your working on a track machine, this is the part that is an absolute PITA because it's difficult to get to these components from the top. You have my sympathy, use your own favorite swear words for the cuss fest. Once you have the links connected to the spools, now you can tighten the linkage mounting bolt on the right pedal.

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    Well, we're done. You now have your new seals installed and are good to go. Don't forget to remove your drain pan from under machine. Somehow, Murphy's Law will insure you'll run over it and squash it.
    Last edited by willie59; 05-31-2010 at 12:21 PM.
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  9. #9
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    hey attco going to walts hitchen post for ribs tonight them fingers look as if they could use a good barbaq sause treatment

  10. #10
    Super Moderator willie59's Avatar
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    Quote Originally Posted by mljohn View Post
    hey attco going to walts hitchen post for ribs tonight

    WHAT!!!

    Grrrrrrrrrrrr

    LoL...enjoy them bro. Dey is finger lickin' good ribs.
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  11. #11
    Senior Member qball's Avatar
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    atco, i need a heart valve replaced, what do you charge?
    SO MOTE IT BE.
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  12. #12
    Super Moderator willie59's Avatar
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    Quote Originally Posted by qball View Post
    atco, i need a heart valve replaced, what do you charge?

    Ummmmm, I think your model may be obsolete. So solly.
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  13. #13
    Senior Member alrman's Avatar
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    Awesome post ATCO !
    Things a bit quiet at work? I mean, being able to document your job - hope the customer doesn't recognize his machine - he might want a discount !
    Next time do you think you could use a hand model for those close up shots ! - Nice thumbnail

  14. #14
    Senior Member bill onthehill's Avatar
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    Atco, that is a great write up. The truth be told as we age we need to document things so when we have that vague remembrance of doing it before we can dig out the pics to jog our fuzzy thoughts! I have reached the age where I no longer stress myself by trying to work on BOBCATS! Retirement has the benefit of saying NO. I would offer to guide someone younger but the old joints don't contort like they used to.
    Alcohol, Tobacco and Firearms should be a convenience store, not a government agency.

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    Member AndyGrevis's Avatar
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    A good mechanic isn't expensive, he's priceless

    Thanks Atco, fantastic write-up!

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