Hello All,
I have been a user of this site and other forums and have never really been a contributor. I have a B21 and struggle to find much information on it. So I thought that this information might be useful to others.
My control valve for the BT751 Backhoe had starting leaking at the top of the spool valves. None of the local hydro shops would work on it and the dealers wanted $850 to repair it (my cost was $110 for the parts) The kit I show in the picture is way cheaper than buying the O-ring and wiper separately. This is a really easy repair to do, the most time consuming part is the removal and installation of the control valve from the machine.
I only had two spool valves leaking but chose to replace all the wiper seals and O-rings on all six top and bottom since they are all along the same age and since most of the work is removing and installing the control valve I didn't want to have to do again for a while.
The control valve has to be removed from the machine to do this, only my upper seals were leaking but to get to the seals the spool valve has to be removed from the bottom which would be very difficult to do on the machine. Removing it also allowed me to clean the entire valve and repaint it.
Provide here are some pictures (at the bottom of the txt) of the control valve before during and after the repair.
For those that aren't familiar with working with hydraulic components cleanliness is very important as hyd systems are not very tolerant of debris or moisture. So make sure you clean things before beginning work and have sufficient ways of capping/plugging the system while you have it apart.
I used a paint pen to label each fitting and corresponding hose before beginning to take the control valve off. Another way of marking if you have it handy is telephone wire as it has a multitude of colors. The paint pen does get wash off during repair due to the hyd fluid, I just took a pic with my phone to preserve it on the control valve. On the hose side, I didn't have that issue since I had pre cleaned the hoses.
Clean off a reasonable area on your table or bench (ability to lay the parts out), you will need to have some cardboard or rags or pigmat to place the control valve on. As you will get a fair amount of hyd leaking out of the valve as you take it apart. You can remove all of the top plates for each spool valve. I chose to remove one spool valve at a time to limit how many exposed parts I had on the bench at one time.
Each lower spool valve cap is held on with allen head cap screws, once the cap is off you can pull the spool valve out from the bottom. There is a corresponding seal plate (looks like the plate on the top) that will be above the return spring. The lower O-ring and wiper seal will usually come out with the spool valve, but always check to make sure the O-ring is out of its cavity.
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Once the spool valve is removed from the control valve body you can remove the upper O-ring and wiper seal (I just used my finger to remove).
Now that the spool valve is out make sure to inspect it and its bore for wear marks, scratches, nicks, ect? If you have been maintaining the hyd system properly these should be fine. Mine had some wear at the top from passing through the upper wiper seal but when checked with a veneer caliper the dia had not been damaged. The lower spool valve caps had some build up in the bottom of them so I cleaned them with de-greaser.
Make sure the spool is clean and lubricate with clean Hyd fluid, and lubricate the wiper seal and O-ring as well. Install the seal plate, wiper seal (paying attention to orientation) on mine the non-flat side faces the seal plate, then the O-ring.
Once you have the spool valve installed to the point the O-ring is touching the valve body you can use the seal plate to seat the O-ring and wiper seal evenly into the valve body. Then reinstall the lower cap.
Then you can install the O-ring and wiper seal (lubricate first), the O-ring goes on first then the wiper seal, again the non-flat surface is facing the seal plate. Install seal plate and use it to seat the O-ring and wiper seal evenly.
The others go together the same way.
My leaks were fixed and all functions of the backhoe worked better. Thanks for reading.
View attachment 661496View attachment 661497View attachment 661498View attachment 661499View attachment 661500View attachment 661502View attachment 661501View attachment 661503View attachment 661504
I have been a user of this site and other forums and have never really been a contributor. I have a B21 and struggle to find much information on it. So I thought that this information might be useful to others.
My control valve for the BT751 Backhoe had starting leaking at the top of the spool valves. None of the local hydro shops would work on it and the dealers wanted $850 to repair it (my cost was $110 for the parts) The kit I show in the picture is way cheaper than buying the O-ring and wiper separately. This is a really easy repair to do, the most time consuming part is the removal and installation of the control valve from the machine.
I only had two spool valves leaking but chose to replace all the wiper seals and O-rings on all six top and bottom since they are all along the same age and since most of the work is removing and installing the control valve I didn't want to have to do again for a while.
The control valve has to be removed from the machine to do this, only my upper seals were leaking but to get to the seals the spool valve has to be removed from the bottom which would be very difficult to do on the machine. Removing it also allowed me to clean the entire valve and repaint it.
Provide here are some pictures (at the bottom of the txt) of the control valve before during and after the repair.
For those that aren't familiar with working with hydraulic components cleanliness is very important as hyd systems are not very tolerant of debris or moisture. So make sure you clean things before beginning work and have sufficient ways of capping/plugging the system while you have it apart.
I used a paint pen to label each fitting and corresponding hose before beginning to take the control valve off. Another way of marking if you have it handy is telephone wire as it has a multitude of colors. The paint pen does get wash off during repair due to the hyd fluid, I just took a pic with my phone to preserve it on the control valve. On the hose side, I didn't have that issue since I had pre cleaned the hoses.
Clean off a reasonable area on your table or bench (ability to lay the parts out), you will need to have some cardboard or rags or pigmat to place the control valve on. As you will get a fair amount of hyd leaking out of the valve as you take it apart. You can remove all of the top plates for each spool valve. I chose to remove one spool valve at a time to limit how many exposed parts I had on the bench at one time.
Each lower spool valve cap is held on with allen head cap screws, once the cap is off you can pull the spool valve out from the bottom. There is a corresponding seal plate (looks like the plate on the top) that will be above the return spring. The lower O-ring and wiper seal will usually come out with the spool valve, but always check to make sure the O-ring is out of its cavity.
-
Once the spool valve is removed from the control valve body you can remove the upper O-ring and wiper seal (I just used my finger to remove).
Now that the spool valve is out make sure to inspect it and its bore for wear marks, scratches, nicks, ect? If you have been maintaining the hyd system properly these should be fine. Mine had some wear at the top from passing through the upper wiper seal but when checked with a veneer caliper the dia had not been damaged. The lower spool valve caps had some build up in the bottom of them so I cleaned them with de-greaser.
Make sure the spool is clean and lubricate with clean Hyd fluid, and lubricate the wiper seal and O-ring as well. Install the seal plate, wiper seal (paying attention to orientation) on mine the non-flat side faces the seal plate, then the O-ring.
Once you have the spool valve installed to the point the O-ring is touching the valve body you can use the seal plate to seat the O-ring and wiper seal evenly into the valve body. Then reinstall the lower cap.
Then you can install the O-ring and wiper seal (lubricate first), the O-ring goes on first then the wiper seal, again the non-flat surface is facing the seal plate. Install seal plate and use it to seat the O-ring and wiper seal evenly.
The others go together the same way.
My leaks were fixed and all functions of the backhoe worked better. Thanks for reading.
View attachment 661496View attachment 661497View attachment 661498View attachment 661499View attachment 661500View attachment 661502View attachment 661501View attachment 661503View attachment 661504
