Thomas BH 108 backhoe

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Jyuma1

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Oct 23, 2022
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Some of you may remember me... I was a regular contributor 10 years ago, but life got in the way and I got busy with other things.
I couldn't remember my password and the email address I used 10 years ago is long gone so I created a new profile. I am now Juma1 but 10 years ago I was just Jyuma.

Believe it or not I'm back on the rebuild of my Thomas BH 108. When I left off 10 years ago I had just removed all the hydraulic lines and now 10 years later I'm trying to install the new lines, but I can't remember how the boom cylinder hydro line get routed.

If anyone has a picture of how the hydro lines are routed to the boom cylinder it would be greatly appreciated.

Thanks
 

Jyuma1

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Oct 23, 2022
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Somebody out there must own a Thomas BH 108 backhoe. It came with my Thomas T133 skid steer when I bought it in the late 80's.
 

Jyuma1

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OK. I guess no body on this forum has a Thomas BH 108 backhoe. No worries, I finally got the old 108 re-plumbed.
All the hydraulic lines are new as are all the fittings. I also replaced the 6 function hydraulic valve.

Now for my next problem. The auxiliary hydraulic couplers on the front of the loader are bi-directional but for operating a backhoe the foot petal that engages the aux output has a detent that locks it in the up (toe) position. What I can't find is any reference to P or T (pump or tank) for when the foot petal is in the up (toe) position. My hydraulic valve on the backhoe has the input and output marked with a "P" and a "T" but the loader auxiliary couplers are not marked. So with the auxiliary power petal engaged in the up (toe) or backhoe position... which coupler is "P" and which is "T"?
Is my question clear as mud?
 

AJ-17

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Feb 27, 2019
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I have a 1997 T-133 with the hydraulic petal that you have. My center petal would not lock so I took apart the top center spool valve in the engine compartment. Got it to lock now! Just wish I could find a backhoe attachment for it. Just can not seem to find one close to Seattle.

To answer your question, just hook it up. Got a 50-50 chance. Does not work, switch the fittings
 

Jyuma1

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Oct 23, 2022
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I did just that... I hooked up the auxiliary hydraulic lines and tried it out. It appears to work just fine. The only problem I found (other than multiple connections I didn't fully tighten) was with the leveling cylinders. The left side works as expected, back on the control extends the cylinder and forward on the control retracks the cylinder. but the right side works the opposite way. No big deal to reverse the hydraulic lines at the valve.

I was actually surprised by how well the old BH 108 worked. I lowered the boom cylinder to the halfway point and left it there, fully expecting it to bleed down over time... but it didn't. Impressive.

Here are some pictures of the now fully functional backhoe.

Full view of backhoe.
Backhoe1.jpg


Front view of control.
Backhoe2.jpg


Lots of new hydraulic lines.
Backhoe3.jpg
 

Jyuma1

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Oct 23, 2022
Messages
23
I have a dumb question... maybe.

The new control valve on my BH 108 is very stiff and in some (one or two) of the spools it doesn't return to neutral on it's own, I need to push the lever back to neutral.

When I asked which of the auxiliary ports were "P" and "T", the response was to just hook it up and try it, which was a good suggestion. When I did that the controls worked so I thought that was that, but now I'm not so sure.

Why should a brand new control valve be stiff and jerky to the point of making the smooth operation of the machine almost impossible? I'm beginning to believe it makes a difference which port connects to "P" and which connects to "T"... why else would they bother to stamp a "P" on one port and a "T" on the other?
 

Mustang Guy

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Apr 12, 2016
Messages
74
In hydraulic jargon "P" stands for pump, and "T" stands for tank. You want the pump pressure to go into the "P" port, and the "T" port goes to the cylinders, or whatever you're trying to operate. And yes, it does make a difference.
 

Jyuma1

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Oct 23, 2022
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In hydraulic jargon "P" stands for pump, and "T" stands for tank. You want the pump pressure to go into the "P" port, and the "T" port goes to the cylinders, or whatever you're trying to operate. And yes, it does make a difference.
Thank you for your response.
I already knew that "P" and "T" meant pump and tank but what I don't know is which port on the auxiliary hydraulic quick disconnects on the T133 loader is "P" when the center foot pedal is engaged in the backhoe position (toe).

The T133 loader auxiliary ports are powered from the center foot pedal. Toe engages a lock detent which keeps the hydraulic fluid flowing to the auxiliary ports and heal (down) reverses the flow (like open a grapple) but does not have a detent, it disengages (returns to neutral) when you lift your heal.

The center pedal obviously reverses the "P" and "T" designations of the auxiliary power takeoff but nothing in the manual says anything about which port is "P" when the center pedal is locked in the toe position (for backhoe operation).

Last night I reversed the hydraulic lines that feed the backhoe. I'll try it out later today and report back.

Thanks for your help.

Update:
Reversing the hydraulic supply lines to the backhoe did the trick. The control works much smoother now and the spools that were sticking are now returning freely. Unfortunately, the controls all work backwards. It's not difficult to correct, but it is a royal PITA.

Here's a picture of where I need to reverse the hydraulic lines. There are 12 of them, with the lower row being impossible to get wrenches on. I ordered a set of large crows feet wrenches. I only need a 3/4, 7/8 and 15/16 sizes but ordering a full set was cheaper than ordering 3 individually.
BackhoeHydraulicLines.jpg

Years ago, someone on this forum once said "happiness is a shiny bucket". Here's hoping my bucket is shiny by the end of the day. :)
 
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Jyuma1

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Oct 23, 2022
Messages
23
Good news! Hope you ordered this type of crow's foot.

View attachment 2724
I looked at that style but decided against. My reasoning was that because I need to reverse "all" the connections, I can remove the entire top row which makes getting to the bottom row much easier, and then do the bottom row.

I finished the day with a partially shiny bucket. My project was to install a drywell about 50 feet away from the house. I dug the trench and 95% of the hole for the drywell but when making the final pulls to flatten out the bottom of the hole... disaster struck. The gland seal blew on the boom cylinder. Naturally the boom cylinder is buried inside the boom so it's the worst one to get to.

The good news is that all 3 cylinders... the boom, the dipper and the bucket... all the same part#. Given the age of the cylinders and the fact that none have been replaced for 30 years, I'll order 3 gland seals and replace them all at the same time.
 

Jyuma1

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Oct 23, 2022
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Well, Murphy strikes again. I can't find a gland seal kit for my backhoe.
The cylinder has a number stamped on it... CTD C30 138A but that number cross references to nothing.
I'm guessing I'll need to eyeball the original seal but I don't know how critical the sizing is. I removed one of the seals and by some miracle it came out fully intact but it's hard to get an exact dimension as the seal isn't exactly round. I know the ID is 1.5" because that's the size of the rod. I also know the grove the seal sits in is between .325 to .330 (hard to believe 5 thousands of an inch would make much difference). The only other dimension would be the OD of the seal and there's where I run into a big question mark. I have no problem measuring the OD by placing the seal on the rod (makes it round) but I would expect that the seal is compressed after all these years of sitting inside the gland nut. It measures 1.887 but that's likely smaller than what a new seal should be. What to do? :unsure:
 

Jyuma1

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Oct 23, 2022
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wings5j

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Jan 7, 2008
Messages
166
My backhoe is an old 1969 Davis D-100. When one of my cylinders started leaking, I took it all apart and brought the seals into a cylinder repair shop that also has a retail parts counter.

Not only were they able to match all of the seals, etc. but at a reasonable price. So reasonable that I bought a full extra set to have in stock at my shop as all three cylinders of the D-100 are identical.

Hopefully you can get it sorted out.

John
 

Jyuma1

Member
Joined
Oct 23, 2022
Messages
23
My backhoe is an old 1969 Davis D-100. When one of my cylinders started leaking, I took it all apart and brought the seals into a cylinder repair shop that also has a retail parts counter.

Not only were they able to match all of the seals, etc. but at a reasonable price. So reasonable that I bought a full extra set to have in stock at my shop as all three cylinders of the D-100 are identical.

Hopefully you can get it sorted out.

John
Thanks.
I took a drive to my local Hydraulic Seals and Hose company. The owner is very helpful but even he had a hell of a time matching the gland seal.

He sold me some seals he thinks will work but are narrower than the grove in the gland nut. He gave me some nylon looking spacers to fill the gap in the grove. He said it doesn't really matter that the seal can move back and forth in the grove, but he prefers to add the spacers to stop the movement.

It's a time-consuming thing to put the 3 cylinders back in just as a test if they work but I guess that's what I'm going to do.

I'll post the results.

Update:
I just ordered seals and wipers from Cylinder Repair Components in Alabama. The measurements look spot on, but I won't know for sure until they get here.
 
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