Thomas Backhoe

[Jyuma]

Am I seeing what I think I'm seeing? Are there like 6 “O” rings inside the machined hydro valve?
I removed the first spool. Here is a picture...

It looks like at least 4 “O” rings would be required... one to the right of the spring in the picture and one to the left of the flat with the hole in it. And one for each of the two lands with the machined grooves. But when I look inside the hole bored in the block that the spool came out of (pictured below) it looks like there are six “O” rings but it is very difficult to see inside the bored hole to be sure.

Is it your experience that there are as many as 6 “O” rings for each spool? I suppose I could try a long angled pick and see if I can remove the “O” rings but how would I get the new ones all the way to where they go inside that long narrow hole? Is there a special trick to it? Like maybe fold the “O” ring over on itself and just work it to the grove inside the hole and then let the “O” ring seek it's original shape inside the groove? I never had to put “O” rings that far down a bore before.

On closer examination it looks like there are only two “O” rings per spool. One that rides to the right of the spring (in the picture) and one the rides to the left of the flat with the hole. There are no other “O” rings in the bore which means it must be a machined fit... but I don't understand how that could possibly seal well enough. I guess I just don't understand how this valve is supposed to work
The “O” ring at the top (the end of the spool with the flat) had a little piece missing from the inside sealing surface. I suppose that could have been one of my leaks.
Here is a highly magnified picture of the damaged area of the “O” ring. I shot the picture through a magnifying desk lamp and a hand held magnifying glass.

 

[Tazza]

On closer examination it looks like there are only two “O” rings per spool. One that rides to the right of the spring (in the picture) and one the rides to the left of the flat with the hole. There are no other “O” rings in the bore which means it must be a machined fit... but I don't understand how that could possibly seal well enough. I guess I just don't understand how this valve is supposed to work
The “O” ring at the top (the end of the spool with the flat) had a little piece missing from the inside sealing surface. I suppose that could have been one of my leaks.
Here is a highly magnified picture of the damaged area of the “O” ring. I shot the picture through a magnifying desk lamp and a hand held magnifying glass.

The spool to housing fit is really tight, that's how it keeps the oil sealed. The rings you see machined into the spool i believe are for lubrication. It just keeps the spool sliding inside the housing easier. The large grooves obviously are used to direct the fluid. The channels you see inside are also for fluid, except for the two ends which have seals.
When you put it back together, make sure the spools slide in and out freely, if not, rotate them 180 degrees. Some times they can bind up, but rotating them should fix the problem.
The missing chunk of seal i also believe to be your problem. Make sure you oil everything up when putting it back together, oil never hurts in these situations, more is better.

 

[Jyuma]

The spool to housing fit is really tight, that's how it keeps the oil sealed. The rings you see machined into the spool i believe are for lubrication. It just keeps the spool sliding inside the housing easier. The large grooves obviously are used to direct the fluid. The channels you see inside are also for fluid, except for the two ends which have seals.
When you put it back together, make sure the spools slide in and out freely, if not, rotate them 180 degrees. Some times they can bind up, but rotating them should fix the problem.
The missing chunk of seal i also believe to be your problem. Make sure you oil everything up when putting it back together, oil never hurts in these situations, more is better.

I took all the spools out and it looks like 2 of them need to be replaced. The photo below is a close-up view of #6 spool. Notice the area just to the left of the flat end of the spool. Most of the area that is corroded away actually sits outside of the valve body, but the “O“ ring is only .100 (one hundred thousandths) of an inch inside the body and the spool moves a lot more than .100 inches, so I'm sure the corroded area will prevent the “O“ ring from sealing on a spool “in“ condition.

Here is a full view of the spool. Any ideas about where I could get one (or two)?

 

[Tazza]

I took all the spools out and it looks like 2 of them need to be replaced. The photo below is a close-up view of #6 spool. Notice the area just to the left of the flat end of the spool. Most of the area that is corroded away actually sits outside of the valve body, but the “O“ ring is only .100 (one hundred thousandths) of an inch inside the body and the spool moves a lot more than .100 inches, so I'm sure the corroded area will prevent the “O“ ring from sealing on a spool “in“ condition.

Here is a full view of the spool. Any ideas about where I could get one (or two)?

You won't get a new one. They are more or less matched to the bore of the control block.
If a small leak isn't a big issue, can you move the segments for the stabiliser legs and put the damaged ones for the stabilisers? Shuffling the segments around won't cause any issues, they are designed to be able to make a huge bank or a single one, all depending on the amount of segments you use.
Depending on what tools and people you have available, you may be able to get the corroded parts welded up, or built up with spray weld and grind it back. This section has relatively low pressure on it, lower than the machines full hydraulic pressure at least. All you need is to get the surface smooth, even something like JB weld and machine it back so its smooth?
There are places that will re-chrome the rod, but it will cost you. The problem is the sealing surface, not the main control part.
Sorry i can't give you better advise than that....

 

[Jyuma]

You won't get a new one. They are more or less matched to the bore of the control block.
If a small leak isn't a big issue, can you move the segments for the stabiliser legs and put the damaged ones for the stabilisers? Shuffling the segments around won't cause any issues, they are designed to be able to make a huge bank or a single one, all depending on the amount of segments you use.
Depending on what tools and people you have available, you may be able to get the corroded parts welded up, or built up with spray weld and grind it back. This section has relatively low pressure on it, lower than the machines full hydraulic pressure at least. All you need is to get the surface smooth, even something like JB weld and machine it back so its smooth?
There are places that will re-chrome the rod, but it will cost you. The problem is the sealing surface, not the main control part.
Sorry i can't give you better advise than that....

Tazza (or anybody else who might know)

I can't find any information on the Kontak valves used in my backhoe other than Kontak may have been bought by Commercial Intertech which may have been absorbed by Parker Hydraulics. I even searched eBayUK (made in UK is cast in the side of the valve) and only found 1 listing for a Kontak valve and it was an old piece of crap 2 spool.
What do you think of this valve? It is a Prince 6 spool that looks perfect for my machine... at least physically it looks well suited. If nothing else... at least the price is right at about $450 USD.

http://cgi.ebay.com/Prince-Manufact...ic_Hydraulic_Valves_Parts&hash=item53e806bd32
It looks like it is perfect as a replacement for the Kontak mono-block that is in my machine but I don't have any specs on the current valve so I don't know if 8 gpm is enough flow for my backhoe. I think the 3500 psi is OK and even the #8 oring in/out ports.
One other thing... I went to the Prince site and downloaded the spec sheets on the valve. There is a notation on the spec sheet about the output port, it says that this port “must” return to the tank. I guess that would not be a problem in that my PTO pedal only locks in one position so the flow of hydro to the new valves would always be in the same direction (in other words the “must” return to the tank would be satisfied) but it is possible to engage (although not lock) the flow in the opposite direction. I have no clue what would happen to the Prince valve if the flow were to be temporarily reversed.

 

[Tazza]

Tazza (or anybody else who might know)
I can't find any information on the Kontak valves used in my backhoe other than Kontak may have been bought by Commercial Intertech which may have been absorbed by Parker Hydraulics. I even searched eBayUK (made in UK is cast in the side of the valve) and only found 1 listing for a Kontak valve and it was an old piece of crap 2 spool.
What do you think of this valve? It is a Prince 6 spool that looks perfect for my machine... at least physically it looks well suited. If nothing else... at least the price is right at about $450 USD.


http://cgi.ebay.com/Prince-Manufacturing-6-Spool-Hydraulic-Valve-8-GPM-NEW-/360375041330?pt=Pneumatic_Hydraulic_Valves_Parts&hash=item53e806bd32
It looks like it is perfect as a replacement for the Kontak mono-block that is in my machine but I don't have any specs on the current valve so I don't know if 8 gpm is enough flow for my backhoe. I think the 3500 psi is OK and even the #8 oring in/out ports.
One other thing... I went to the Prince site and downloaded the spec sheets on the valve. There is a notation on the spec sheet about the output port, it says that this port “must” return to the tank. I guess that would not be a problem in that my PTO pedal only locks in one position so the flow of hydro to the new valves would always be in the same direction (in other words the “must” return to the tank would be satisfied) but it is possible to engage (although not lock) the flow in the opposite direction. I have no clue what would happen to the Prince valve if the flow were to be temporarily reversed.

I can't see why the 8gpm wouldn't work. You don't need loads of oil going to the bankhoe attachment. On my 743 that puts out about 11gpm, i run it at at around 1/3 to 1/2 throttle, it responds just fine, i have never needed to run it flat out to get the 11gpm from it.
I suspect where it states the port must go back to the tank is because the seals may not be rated for it. Generally the seals that you are having issues with on the spools run at low pressure, if the flow was reversed you would have the full pressure on them and could damage them.

 

[Jyuma]

I can't see why the 8gpm wouldn't work. You don't need loads of oil going to the bankhoe attachment. On my 743 that puts out about 11gpm, i run it at at around 1/3 to 1/2 throttle, it responds just fine, i have never needed to run it flat out to get the 11gpm from it.
I suspect where it states the port must go back to the tank is because the seals may not be rated for it. Generally the seals that you are having issues with on the spools run at low pressure, if the flow was reversed you would have the full pressure on them and could damage them.

Thanks.
I emailed Thomas tech support and they emailed back that the valve assembly is still listed as available (really?) but it's not in stock. They are checking on lead time and will get back to me.
In the meantime... you had mentioned the possibility of switching the valves around... and that got me thinking (great idea) but then I noticed that the stabilizer spools have a different attachment point design than the other spools.
You know I'm fond of pictures right? hehehe In the photo below the spool on the left is from the stabilizer valve and the spool on the right is from the swing valve. The stabilizer spools slide over a stud on the linkage and are held in place with a pin. All the other spools (the other 4) have a flat machined in the end of the spool and a collar slides over the flat and is held in place with a roll pin. The top of the collar has a threaded hole and the joystick gimbals screw onto the top of the spools. In other words... they are not interchangeable.

 

[Jyuma]

Thanks.
I emailed Thomas tech support and they emailed back that the valve assembly is still listed as available (really?) but it's not in stock. They are checking on lead time and will get back to me.
In the meantime... you had mentioned the possibility of switching the valves around... and that got me thinking (great idea) but then I noticed that the stabilizer spools have a different attachment point design than the other spools.
You know I'm fond of pictures right? hehehe In the photo below the spool on the left is from the stabilizer valve and the spool on the right is from the swing valve. The stabilizer spools slide over a stud on the linkage and are held in place with a pin. All the other spools (the other 4) have a flat machined in the end of the spool and a collar slides over the flat and is held in place with a roll pin. The top of the collar has a threaded hole and the joystick gimbals screw onto the top of the spools. In other words... they are not interchangeable.

And for my next dumb question... What is a #8 SAE “O“ ring port?
Here is a picture of the fittings that are connected to the work ports on my existing valve. There are 12 of them... 2 for each valve segment. The straight thread (shown on the left of the fitting in the photo below) threads into the valve body. The flared thread on the right connects to the various hydraulic hoses.
The straight thread outside diameter is .868 (22.07 mm). The flared side outside diameter is .740 (18.8 mm).
You will notice that there is an “O” ring on the left side placed in a groove between the threads and the hex. Based on the dimensions I've reported... is this fitting a #8 “O” ring fitting? If it isn't a #8 “O” ring fitting then what is it?

There are also two fittings (one shown below) that connect the PTO to the backhoe that are of the same basic design as the others, right down to the “O“ ring. The straight thread on the left is larger than the other 12 fittings, with an outside diameter of 1.055 (26.78 mm) but the flare is the same. Any idea what SAE # these fittings might be?

Yes... I am seriously considering buying that Prince valve but I first need to be sure that my hose connections will match up correctly. If I can screw my existing fittings (first photo above) into the Prince valve then I am reasonably sure that I can make everything else work.
Thanks
Ed

 

[Tazza]

And for my next dumb question... What is a #8 SAE “O“ ring port?
Here is a picture of the fittings that are connected to the work ports on my existing valve. There are 12 of them... 2 for each valve segment. The straight thread (shown on the left of the fitting in the photo below) threads into the valve body. The flared thread on the right connects to the various hydraulic hoses.
The straight thread outside diameter is .868 (22.07 mm). The flared side outside diameter is .740 (18.8 mm).
You will notice that there is an “O” ring on the left side placed in a groove between the threads and the hex. Based on the dimensions I've reported... is this fitting a #8 “O” ring fitting? If it isn't a #8 “O” ring fitting then what is it?


There are also two fittings (one shown below) that connect the PTO to the backhoe that are of the same basic design as the others, right down to the “O“ ring. The straight thread on the left is larger than the other 12 fittings, with an outside diameter of 1.055 (26.78 mm) but the flare is the same. Any idea what SAE # these fittings might be?


Yes... I am seriously considering buying that Prince valve but I first need to be sure that my hose connections will match up correctly. If I can screw my existing fittings (first photo above) into the Prince valve then I am reasonably sure that I can make everything else work.
Thanks
Ed

The fittings are JIC on one end, the other is ORB? worst case, if the fittings you have dont' screw in, you can get ones that will with the correct JIC fitting at the end for the tobe lines on the machine.
Its a shame you can't use the stabiliser ones on it... But yeah, they are very different.
The only other way you could try is to get the rusted section machined down and sleeved. Its worth a try, if it fails you have lost nothing. I'd be pretty confident that even with my machining abilities that i could get it pretty close if not just right. A machine shop shouldn't have an issue.

 

[Jyuma]

The fittings are JIC on one end, the other is ORB? worst case, if the fittings you have dont' screw in, you can get ones that will with the correct JIC fitting at the end for the tobe lines on the machine.
Its a shame you can't use the stabiliser ones on it... But yeah, they are very different.
The only other way you could try is to get the rusted section machined down and sleeved. Its worth a try, if it fails you have lost nothing. I'd be pretty confident that even with my machining abilities that i could get it pretty close if not just right. A machine shop shouldn't have an issue.

Tazza, you give me great information even when you don't know you're giving me great information.

You used the term ORB... not knowing what ORB was I Googled it and found the following... http://fittingsandadapters.com/saej5straigt.html
Now I know how to measure O-Ring Boss fittings and I know that I don't have -8's, I have -10's

Maybe that Prince valve isn't such a great fit.

Thanks a million.

 

[Jyuma]

Tazza, you give me great information even when you don't know you're giving me great information.
You used the term ORB... not knowing what ORB was I Googled it and found the following... http://fittingsandadapters.com/saej5straigt.html
Now I know how to measure O-Ring Boss fittings and I know that I don't have -8's, I have -10's
Maybe that Prince valve isn't such a great fit.
Thanks a million.

Thomas got back to me this morning... they cannot supply any replacement parts for the Kontak valve used in the early model BH108 backhoe. They have not yet determined if they can supply the entire valve assembly but my guess would be no!
Probably my only hope from Thomas would be if I can adapt whatever valve assembly they are currently using on their BH108 backhoe to the BH108 of 25 years ago but I'd bet the price will make you...

 

[jerry]

Thomas got back to me this morning... they cannot supply any replacement parts for the Kontak valve used in the early model BH108 backhoe. They have not yet determined if they can supply the entire valve assembly but my guess would be no!
Probably my only hope from Thomas would be if I can adapt whatever valve assembly they are currently using on their BH108 backhoe to the BH108 of 25 years ago but I'd bet the price will make you...

I would go with Tazza's suggestion first. I believe those spools can be saved either by metaliziing and grinding or sleeving. Find a decent machine shop and get a opinion before replacing the whole valve. It still may cost a few hundred bucks but worth checking into.

 

[Jyuma]

I would go with Tazza's suggestion first. I believe those spools can be saved either by metaliziing and grinding or sleeving. Find a decent machine shop and get a opinion before replacing the whole valve. It still may cost a few hundred bucks but worth checking into.

I've decided to go with one of Tazza's original suggestions and attempt to fill the pitted areas with J-B Weld. I've already filled the worst (most pitted) spool shaft and now I'm waiting for it to fully cure before light sanding and polishing.
Photo (of course)...

In the photo above, the J-B Weld repair looks a little sunken in but it isn't, that's just an optical allusion. In fact... the repair looks almost perfect.
I was amazed at how nicely the J-B Weld filled in the tiny craters and depressions in the shaft. I used the good portion of the spool shaft to guide a 2“ plastic taping knife, and then I rotated the spool to spread the J-B Weld into and around the shaft.
I think this may actually work.

 

[Tazza]

I've decided to go with one of Tazza's original suggestions and attempt to fill the pitted areas with J-B Weld. I've already filled the worst (most pitted) spool shaft and now I'm waiting for it to fully cure before light sanding and polishing.
Photo (of course)...

In the photo above, the J-B Weld repair looks a little sunken in but it isn't, that's just an optical allusion. In fact... the repair looks almost perfect.
I was amazed at how nicely the J-B Weld filled in the tiny craters and depressions in the shaft. I used the good portion of the spool shaft to guide a 2“ plastic taping knife, and then I rotated the spool to spread the J-B Weld into and around the shaft.
I think this may actually work.

Hopefully it will work, its not a wear area. As long as its smooth enough for the seal to seal against i can't see why it won't work.
Keep the pictures coming!

 

[Jyuma]

Hopefully it will work, its not a wear area. As long as its smooth enough for the seal to seal against i can't see why it won't work.
Keep the pictures coming!

Here is the same spool after wet sanding with 800 paper. It looks like it would work just fine but to be extra sure I went and bought a stronger version of J-B Weld for the other two spools that need repair. The J-B Weld used on this spool is good to 300 degrees F. The J-B Weld I used on the next two spools is good to 600 degrees F. I doubt that the spools will even get anywhere near 300 F but why not use the stronger one.

Below is a photo of the other two spools before the repair. We'll just have to wait until tomorrow for the after photos because the stronger stuff takes 15 hours to cure.
The numbered flags tie-wrapped to the end of the spools is the number of the valve it came from. The reason the other spool doesn't have a number is because it's #6 and the only one not numbered... so I know it has to be #6. (Yes, I numbered the valves too).

 

[SkidRoe]

Here is the same spool after wet sanding with 800 paper. It looks like it would work just fine but to be extra sure I went and bought a stronger version of J-B Weld for the other two spools that need repair. The J-B Weld used on this spool is good to 300 degrees F. The J-B Weld I used on the next two spools is good to 600 degrees F. I doubt that the spools will even get anywhere near 300 F but why not use the stronger one.


Below is a photo of the other two spools before the repair. We'll just have to wait until tomorrow for the after photos because the stronger stuff takes 15 hours to cure.
The numbered flags tie-wrapped to the end of the spools is the number of the valve it came from. The reason the other spool doesn't have a number is because it's #6 and the only one not numbered... so I know it has to be #6. (Yes, I numbered the valves too).

Somebody in a previous post mentioned swapping the two badly pitted sections to the ones used for the outriggers; still seems like a goot idea to me, just to be safe.
Normal operating temperature for a well maintained hydraulic system is 160-180°F. If you get to 300°F, you have bigger problems.
Good luck. I like what you have done, let us know how it works.

 

[Jyuma]

Somebody in a previous post mentioned swapping the two badly pitted sections to the ones used for the outriggers; still seems like a goot idea to me, just to be safe.
Normal operating temperature for a well maintained hydraulic system is 160-180°F. If you get to 300°F, you have bigger problems.
Good luck. I like what you have done, let us know how it works.

Thanks for the kind words SkidRoe... it's much appreciated.
The J-B Weld worked way better than I expected. After the second batch cured I wet sanded the race (with 800 grit) where the “O“ rings ride on the spools and by the time I was done I couldn't feel the transition from the original metal to the repair when I ran my finger over the area with my eyes closed. I figure if I can't feel it, neither can the “O” ring.

I didn't bother taking more pictures of the repaired spools... they look pretty much just like the photo I posted of the first repaired spool.
So rather than post what you've already seen, I took a shot of the entire valve assembly with the six spools installed. I gotta admit... I was a bit nervous about pushing the spools past the new “O“ rings. I made sure I used a lot of lubrication (is there any such thing as too much?). The initial insertion wasn't all that bad but when those machined grooves slide past the “O” ring you can feel each one as they slide inside the “O” ring. Scary stuff but I figured they didn't grow there when the valve was new so somebody had to have done this before, it must be OK.

Counting from left to right, the repaired spools are 1, 2 and 6. If you look closely you can see the repairs... they show as gray patches just above where the spool comes out of the valve body. The photo clearly shows that #6 required the most attention. The entire area above the valve body of #6 is essentially all J-B Weld but it is as smooth as silk and the spool moves in and out with comparative ease (once you overcome the tension of the return spring) .
Spools 3 and 4 are the stabilizer spools and this photo shows why I couldn't just move valves around... the shaft ends are totally different on the stabilizer spools.
bTw... The white fittings you see are PVC plugs I used to keep stuff out of the valves while I was cleaning the crud off the outside. I had tape over the two on the right but removed it before the picture was taken.

 

[Jyuma]

Thanks for the kind words SkidRoe... it's much appreciated.
The J-B Weld worked way better than I expected. After the second batch cured I wet sanded the race (with 800 grit) where the “O“ rings ride on the spools and by the time I was done I couldn't feel the transition from the original metal to the repair when I ran my finger over the area with my eyes closed. I figure if I can't feel it, neither can the “O” ring.
I didn't bother taking more pictures of the repaired spools... they look pretty much just like the photo I posted of the first repaired spool.
So rather than post what you've already seen, I took a shot of the entire valve assembly with the six spools installed. I gotta admit... I was a bit nervous about pushing the spools past the new “O“ rings. I made sure I used a lot of lubrication (is there any such thing as too much?). The initial insertion wasn't all that bad but when those machined grooves slide past the “O” ring you can feel each one as they slide inside the “O” ring. Scary stuff but I figured they didn't grow there when the valve was new so somebody had to have done this before, it must be OK.

Counting from left to right, the repaired spools are 1, 2 and 6. If you look closely you can see the repairs... they show as gray patches just above where the spool comes out of the valve body. The photo clearly shows that #6 required the most attention. The entire area above the valve body of #6 is essentially all J-B Weld but it is as smooth as silk and the spool moves in and out with comparative ease (once you overcome the tension of the return spring) .
Spools 3 and 4 are the stabilizer spools and this photo shows why I couldn't just move valves around... the shaft ends are totally different on the stabilizer spools.
bTw... The white fittings you see are PVC plugs I used to keep stuff out of the valves while I was cleaning the crud off the outside. I had tape over the two on the right but removed it before the picture was taken.

I put the valve back in the machine and fired her up... the good news is that none of the spools that I fixed are leaking and they even operate perfectly. The bad news is that #5 spool (one that didn't need any work) is leaking... and at a high enough rate to make it unacceptable.

From what I can see (it's tough to see with the valve mounted in the machine) it looks like the lower “O” ring might be leaking. I could have damaged it or pushed it out of it's groove when I installed the #5 spool. Oh well... what's a couple of more hours work compared to the week it's taken me to get this far? At least it looks like the J-B Weld is working.

I never took the valves apart... by that I mean I didn't separate the segments. The 6 valves bolt together much like the old cast iron radiator sections did. I didn't take them apart because I thought that was just asking for trouble but I guess it is possible that the “O” rings that seal between valve 5 and 6 could be leaking. It's really very hard to tell.

 

[Tazza]

I put the valve back in the machine and fired her up... the good news is that none of the spools that I fixed are leaking and they even operate perfectly. The bad news is that #5 spool (one that didn't need any work) is leaking... and at a high enough rate to make it unacceptable.
From what I can see (it's tough to see with the valve mounted in the machine) it looks like the lower “O” ring might be leaking. I could have damaged it or pushed it out of it's groove when I installed the #5 spool. Oh well... what's a couple of more hours work compared to the week it's taken me to get this far? At least it looks like the J-B Weld is working.
I never took the valves apart... by that I mean I didn't separate the segments. The 6 valves bolt together much like the old cast iron radiator sections did. I didn't take them apart because I thought that was just asking for trouble but I guess it is possible that the “O” rings that seal between valve 5 and 6 could be leaking. It's really very hard to tell.

Great news!
There are O rings between segments, so its pretty easy to re-seal it.
It does sound like you may have pincehd the quad ring when installing number 5 spool, at least its a reasonably easy fix, especially vs what you have already done!

 

[Jyuma]

Great news!
There are O rings between segments, so its pretty easy to re-seal it.
It does sound like you may have pincehd the quad ring when installing number 5 spool, at least its a reasonably easy fix, especially vs what you have already done!

I pulled the valve out again and removed the #5 spool. Below are two close-up views of what was a brand new lower “O” ring. The first photo shows damage to approx half the circumference of the “O” ring.
Link to the full resolution image.

This next photo is a super close-up of a portion of the damaged area.
Link to full resolution image.

I assume the “O” ring was damaged when I inserted the spool... those machined grooves in the spool are like razors... but I don't know what else I can do when inserting the spool other than flooding it with oil and going slow (with a turning action).
Any ideas how to prevent damage to the “O” ring while inserting the spool?