How to install bypass valve so that thumb follows bucket?

[etpm]

Asking for a friend. He has a CAT excavator that weighs about 9000 pounds. I don't know the model. He was complaining that the thumb doesn't follow the bucket. I seem to recall reading on TBN somewhere that a bypass valve that bypasses fluid to the retract hose on the thumb cylinder can be installed to make the thumb follow the bucket. I guess the valve that actuates the thumb may also need a detent installed if possible to keep pressure on the thumb. Anyway, I don't know how to do this or if it an easy thing to do so I'm asking here.
Thanks Folks,
Eric

 

[Seven Gables]

Asking for a friend. He has a CAT excavator that weighs about 9000 pounds. I don't know the model. He was complaining that the thumb doesn't follow the bucket. I seem to recall reading on TBN somewhere that a bypass valve that bypasses fluid to the retract hose on the thumb cylinder can be installed to make the thumb follow the bucket. I guess the valve that actuates the thumb may also need a detent installed if possible to keep pressure on the thumb. Anyway, I don't know how to do this or if it an easy thing to do so I'm asking here.
Thanks Folks,
Eric

If I’m understanding what you’re asking it’s really quite easy. There should be circuit reliefs threaded into each side of the thumb valve in the main valve stack.
You’ll need a 5000psi pressure guage plugged into the quick coupler that supplies oil to thumb cylinder base end .
Activate the thumb extend button and read the guage to see what the circuit relief is currently set at . Most all the circuit reliefs I’ve seen are simply a Allen head screw with a jam nut , counterclockwise reduces pressure, clockwise increases pressure it reliefs at.
You’ll need to know what cat recommends for the relief pressure for that machine, usually in the 2000-2500psi range. Make sure you’re adjusting the one that supplies oil to thumb cylinder base end.
A picture of the thumb valve would be helpful. Here’s a pic of the circuit relief on my Volvo. If you’ve got questions ask away.

 

[etpm]

If I’m understanding what you’re asking it’s really quite easy. There should be circuit reliefs threaded into each side of the thumb valve in the main valve stack.
You’ll need a 5000psi pressure guage plugged into the quick coupler that supplies oil to thumb cylinder base end .
Activate the thumb extend button and read the guage to see what the circuit relief is currently set at . Most all the circuit reliefs I’ve seen are simply a Allen head screw with a jam nut , counterclockwise reduces pressure, clockwise increases pressure it reliefs at.
You’ll need to know what cat recommends for the relief pressure for that machine, usually in the 2000-2500psi range. Make sure you’re adjusting the one that supplies oil to thumb cylinder base end.
A picture of the thumb valve would be helpful. Here’s a pic of the circuit relief on my Volvo. If you’ve got questions ask away.

Thanks for your reply. I will try to get pictures tomorrow. This might be easier than I thought. I may even have a 5000 PSI liquid filled guage that my friend can use. Thanks again,
Eric