I have a cat 308c SR having a little problem with the thumb. With the foot pedal it goes up just fine,going closed it starts to close then stops, I can switch to the articulating boom and that works as it should.I have takin the foot valve apart and cleaned it ,I have removed the cylinder and had it tested. it is good. Could use a little help with the next step
There is either no oil going to cylinder or the cylinder is jamming somehow. Disconnect a hose and plug the end with gauge set up and see what kind of pressure is there. Follow the line back if no pressure to control valve and check if spool hung up. Might be an idea to post Serial number. Any active codes on display. Simon C
I have had the cylinder tested at my local hydraulic shop,but have not reinstalled it yet. In my mind there are three components to the thumb operation, the cylinder, the foot valve and the valve that changes it from the thumb to the articulating boom, I have not located that valve yet, it would be nice if the floor came out of the cab. no codes it is a older machine
I'm pretty sure there is no pressure going to the close position on the thumb, when it step on the foot valve it is just the weight of the the thumb moving it down for a little ways
You have a valve on the boom on some machines to decide whether the oil goes to thumb or somewhere else. You may have a problem with linkage to your contol valve. If you post your serial number Nige may lend a hand. You might as well get floor boards out to see exactly what is going on. Maybe post some pictures and someone else may help. Simon C
I know my excavator is a gray market machine. first picture is the serial numbers, second is the valve that I think is bad, it transfers power form the thumb to the articulating boom. I think
Every thing in there needs to be cleaned before taking anything apart. Once clean you may begin to have a better idea as to what could be wrong. Maybe Nige will see your post now that you have posted the serial number. Simon C
I do plan on cleaning everything up before I take it apart, but it is raining today, no rain for the next few days
I got it figured out, one more question should the boom cylinder be extended or retracted when I check the hydraulic fluid?
What was the solution for others possibly in the future??
This sounds kind of embarrassing, but after two days of removing the cylinder and have it tested, then,taking the foot control valve out cleaning and replacing the o-rings.I found the problem. There are two valves on top of my boom for operating the thumb or the hammer. While I was out in the woods clearing some vine maple, a branch must had got wedged in that valve. I got on top of the boom and found one of the valve handles was broken off and rotated to the hammer mode. I have never used the hammer and do not own one. so the next project is to remove those valves. Not just need to check the fluid level and clean up the toxic spill in the dirt
Post number 5 above says there is a valve on the boom to decide if the oil goes to thumb or elsewhere. Glad I still know where to start looking. Glad you found it. Simon C
There is nothing embarrassing about finding the solution to the problem. Good it was nothing major or expensive