Valve Body Leak on 743

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My 743 developed a serious hydraulic leak, which appeared to be coming out the bottom of the main valve body that runs the lift and tilt functions. After many hours of exploration I determined it was a flex hose that connects to the bottom of the valve. Long story short I finally dug into it and disconnected all of the hard lines and hoses going to the front side of the valve to a point I could get a stubby wrench on the fitting and sure enough it had worked it's way loose to the point the fluid was running out at a rate of 5 gallons in the matter of minutes. I replaced all the hoses, tighten all the fittings and refilled with fluid and waited. No leaks, great, I was feeling pretty good and went in for lunch. When I came back out there was again another puddle of fluid under the unit only this time it was a little smaller so I started it up again and waited, sure enough looking from the engine compartment towards the front the back of the valve body has 2 round caps with 3/16 allen head screws holding them in place and I noticed fluid oozing out from the top one at a pretty good flow. Before I get in too far over my head does any one have any suggestions as to how to approach the latest leak? Thanks, Mike
 

sterlclan

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May 1, 2004
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sounds like a spool seal...Ive done them with the valve body installed not fun seems like you've already had it most of the way apart,might be easiest to remove the valve body and do them on the bench any hydraulic shop should be able to get the seals for you and a service manual is worth every penny.any trouble give us a shout and we will try to help as best we can. welcome to the forum. Jeff
 

jmatt20

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sounds like a spool seal...Ive done them with the valve body installed not fun seems like you've already had it most of the way apart,might be easiest to remove the valve body and do them on the bench any hydraulic shop should be able to get the seals for you and a service manual is worth every penny.any trouble give us a shout and we will try to help as best we can. welcome to the forum. Jeff
there is a thread on here somewhere about this ,i know because i had the same problem. If you are lucky the washer under the cap is broken and the seal is out of place. i was doing a lot of work on my machine so i pulled the engine out. you don't have to pull the engine but if you want to get everything cleaned out in the compartment it only takes about 11/2 to 2 hrs to do it, this is a good time to make sure the radiators don't have excess oily dirt build up. my spool seals wern't leaking just the one on the end , if you get the right allen wrench and pull off the cap ,under it you should find a washer shapped like a sombrero,under that is a square cut o ring ,thats the one i had to replace , the cap on my machine was broken the washer was in pieces and the o ring was all chewed up. the factory has an upgrade for these parts ,a cap with thicker ears ,a steele washer insteed of pot metal ,and i think a new type of washer. your dealer parts guy should be able to find a service bulletin about this.
 

Tazza

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there is a thread on here somewhere about this ,i know because i had the same problem. If you are lucky the washer under the cap is broken and the seal is out of place. i was doing a lot of work on my machine so i pulled the engine out. you don't have to pull the engine but if you want to get everything cleaned out in the compartment it only takes about 11/2 to 2 hrs to do it, this is a good time to make sure the radiators don't have excess oily dirt build up. my spool seals wern't leaking just the one on the end , if you get the right allen wrench and pull off the cap ,under it you should find a washer shapped like a sombrero,under that is a square cut o ring ,thats the one i had to replace , the cap on my machine was broken the washer was in pieces and the o ring was all chewed up. the factory has an upgrade for these parts ,a cap with thicker ears ,a steele washer insteed of pot metal ,and i think a new type of washer. your dealer parts guy should be able to find a service bulletin about this.
It really is MUCH easier if you can pull the valve out, but removing the valve is a real pain. If you remove it, replace that hose under the spool! its only a return line but its a pig to replace when still in the machine (as you have already noticed).
As jmatt20 said, if its leaking from the top cap its almost definatly the spool seal. These valves run a quad ring at the front and back of the spool. Being the top it should be reasonably easy to replace. Un-do the linkage at the front, give it a good clean! remove the 2 allen screws at the front and remove the dust cover, give it another good clean. Remove the 2 allen screws at the back and carefully remove the cover, i can't remember if this is the lift or tilt function, if its lift it will have 2 detent balls that will shoot out. If its tilt its all good, just slide it off. With the cover off grab hold of the spring at the end of the spool and pull the spool out.
With the spool out remove the steel caps front and back and remove the quad rings, you'd be best to get a genuine bobcat kit for this as you know they are rite. Give them a good oil up and slide the cap on the spool and slide the new quad ring on. Oil it up and carefully slide the spool back in. Don't pinch the quad ring or it will be cut and useless. when the back is in, install the front by sliding the new ring on with oil and replace the steel retainer. Replace the cap and dust cover (replace the dust cover if its split). then its all good.
It may sound hard, but sreiously its quite easy.
I have done 4 valves like this, 2 off 743's and the other 2 were off other machines. Just take your time and make sure the seals that go in match what came out unless its an upgrade. Some seals have a rite and wrong way to be installed. Just keep it all clean and you will be fine.
 

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It really is MUCH easier if you can pull the valve out, but removing the valve is a real pain. If you remove it, replace that hose under the spool! its only a return line but its a pig to replace when still in the machine (as you have already noticed).
As jmatt20 said, if its leaking from the top cap its almost definatly the spool seal. These valves run a quad ring at the front and back of the spool. Being the top it should be reasonably easy to replace. Un-do the linkage at the front, give it a good clean! remove the 2 allen screws at the front and remove the dust cover, give it another good clean. Remove the 2 allen screws at the back and carefully remove the cover, i can't remember if this is the lift or tilt function, if its lift it will have 2 detent balls that will shoot out. If its tilt its all good, just slide it off. With the cover off grab hold of the spring at the end of the spool and pull the spool out.
With the spool out remove the steel caps front and back and remove the quad rings, you'd be best to get a genuine bobcat kit for this as you know they are rite. Give them a good oil up and slide the cap on the spool and slide the new quad ring on. Oil it up and carefully slide the spool back in. Don't pinch the quad ring or it will be cut and useless. when the back is in, install the front by sliding the new ring on with oil and replace the steel retainer. Replace the cap and dust cover (replace the dust cover if its split). then its all good.
It may sound hard, but sreiously its quite easy.
I have done 4 valves like this, 2 off 743's and the other 2 were off other machines. Just take your time and make sure the seals that go in match what came out unless its an upgrade. Some seals have a rite and wrong way to be installed. Just keep it all clean and you will be fine.
Thanks everyone, it's great to have a site with such expertise. I have looked at this site a ton but this was my first post and didn't really know what to expect, thanks again.
 

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Thanks everyone, it's great to have a site with such expertise. I have looked at this site a ton but this was my first post and didn't really know what to expect, thanks again.
Thanks Tazza for the "MUCH" needed advise on pulling the valve out of the machine to rebuild, I took that advice and actually once I tore into it it wasn't as bad as it looked to begin with. I have since then reinstalled and have NO leaks. The only question I have now is I have a little whining, growling noice when I operate the controls and I'm assuming it is from the air in the system. Is there a better way of bleeding the air out then just running it or will it just get better the more I use it? (It has gotten better the few times I've been running it.) Thanks again for the help, Mike
 

Tazza

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Thanks Tazza for the "MUCH" needed advise on pulling the valve out of the machine to rebuild, I took that advice and actually once I tore into it it wasn't as bad as it looked to begin with. I have since then reinstalled and have NO leaks. The only question I have now is I have a little whining, growling noice when I operate the controls and I'm assuming it is from the air in the system. Is there a better way of bleeding the air out then just running it or will it just get better the more I use it? (It has gotten better the few times I've been running it.) Thanks again for the help, Mike
Just keep using it, it will bleed out in time. It took ages for mine to clear up! i mean weeks and weeks but its perfect now, no growling or shuddering. Just give it a bit more time.
Glad it was easy enough to fix.
 
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