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I recently had a hydraulic thumb installed on my 1999 436cit…

I recently had a hydraulic...
I recently had a hydraulic thumb installed on my 1999 436cit cat backhoe. It has aux hyd on the hoe but, they only work one way. Is there any way to get the hydraulics to work both ways to open and close the thumb?
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Answered in 4 minutes by:
11/21/2015
Mechanic: catmastertech, Technician replied 7 years ago
catmastertech
catmastertech, Technician
Category: Construction and Road Equipment
Satisfied Customers: 4,041
Experience: Field service technician for CAT 19 years.
Verified

Yes, the valve for the auxiliary section is a two way valve. It is just plumbed for return flow to the tank.

If the install was done correctly, the return line should have a ball valve to close and switch to two-way function.

This all depends on the installation kit used and the machine configuration.

If you have the full machine serial number and the part number of the kits used to add the control and lines, I might find the correct setup for your machine.

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Customer reply replied 7 years ago
the serial number is ***** The aux hydraulics that are plumbed on the boom are factory installed, the machine came set up that way.Were would the valve be located? I am picking up the machine tomorrow from the guy that installed the thumb.
Customer reply replied 7 years ago
The guy that installed the thumb just installed the thumb and the hydraulic ram and connected the lines to the existing aux hydraulic lines on the boom. The machine has a foot lever in the cab that runs the aux hydraulics plumbed on the boom.
Mechanic: catmastertech, Technician replied 7 years ago

Thanks for the serial number. Please allow me some time to research this and I will post back what I can find.

The Auxiliary valve used for hammer one-way flow is also used for two-way flow. You pedal should move both directions. If it does not, look for a locking pin that limits travel in the opposite direction.

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Mechanic: catmastertech, Technician replied 7 years ago

Ok, this is what I could find.

This machine was only equipped with the extendable stick valve used for the auxiliary valve. It was shipped from the factory without any rear lines for attachments so, the customer could setup the machine for either hammer (one way flow) or thumb (two way flow) later and order the appropriate line kit then. (Neither kit was setup to operate both functions from one valve.)

You will need to change the tubes on the valve to allow for two way flow and remove the return line that is connected next to the filter housing.

The upper tube on the valve may work but, you will need to add a lower tube the the valve for two way flow.

See the attached file for the parts needed to use the extendable stick valve for auxiliary valve purposes.

Thanks, Donnie

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Customer reply replied 7 years ago
just to recap, the machine has the valve but just needs the extra lines and the foot valve will operate in both directions
Mechanic: catmastertech, Technician replied 7 years ago

yes

Build ticket shows backhoe valve was built with the extendable stick valve used for the auxiliary function.

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Customer reply replied 7 years ago
I will have to look at the machine to try and understand what you are saying. So when I remove the return line from the filter housing were does it go?
Mechanic: catmastertech, Technician replied 7 years ago

It is removed and the fitting is plugged. If you think you might use a hammer some day, leave it installed if it is not in the way of the other lines.

It is not designed for both lines to run through that side of the frame but, it may not bee in the way.

If it is, then you will need to remove the line and cap the fitting at the filter housing.

The one-way flow send oil to the hammer from the valve and returned it to the filter to reduce back pressure in the circuit.

Two-way flow sends and returns all the oil through the valve.

Both systems use the same valve. The one way just uses one half of the valve.

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Customer reply replied 7 years ago
lower tube that I need to add on the valve connects from the valve to the return line for two way operating and the fitting it was connected to on the filter housing is plugged correct.?
Mechanic: catmastertech, Technician replied 7 years ago

The thumb cylinder line that is currently connected to the machine one-way flow return line will be plugged or removed.

That line will connect to the lower line you add to the valve.

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Customer reply replied 7 years ago
what I replied before is correct then. The return line from the thumb cylinder will be removed from the filter housing and connected to the lower line from the valve that I have to install and the fitting that that return line was connected to the filter housing will be plugged? I'm trying to simplify this. There is a pressure line and a return line on the machine now that only works one way sending return oil to the filter housing. I need to hook that line to a port on the valve with an extra line that I will need to get so that line will act as a pressure line and a return line for two way operating?
Mechanic: catmastertech, Technician replied 7 years ago

Sorry for the late reply, I though we had finished.

Yes, you are correct.

I am sorry I did not explain it better the first time.

If you still need help on this later, please let me know.

I will be glad to help as much as I can.

catmastertech
catmastertech, Technician
Category: Construction and Road Equipment
Satisfied Customers: 4,041
Experience: Field service technician for CAT 19 years.
Verified
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