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Dan, Technician
Category: Construction and Road Equipment
Satisfied Customers: 4878
Experience:  17+ yrs. shop and field experience with all major brands of heavy equipment and trucks - 1995 WyoTech graduate.
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I have a 2000 Caterpillar 226 skid steer. I just bought it

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I have a 2000 Caterpillar 226 skid steer. I just bought it used and it came with no manuals and I'm new to hydraulics but I'm pretty good mechanically. Ok my problem, I'm trying to use a tree shear attachment and run it off the aux connections. I have joy stick controls, the right stick does all hydraulics, I control the opening and closing of the shear with a small waterproof toggle switch on top of the joystick. Right now I cut into a tree and it only cuts about an inch then seems to run out of power. It doesn't bog down the engine. So I started doing checks on hoses and other things just eliminating possible causes. I've ruled out everything in the shear its self and my quick connects by removing and just being able to blow thru them with no problem. So now I'm on to pressure testing. I get a reading of 3500 psi on one aux line when pushing one side of the switch, I switch the gauge to the opposite line, push the toggle in the other direction and get a reading of 0. What is my next step? Possibly checking an electrical connection in the joystick switch itself? I'm over 2 hours from a CAT dealer and can't afford to take it to them or have them send someone out. I can provide pictures of anything that may be needed.

Hi James. My name is***** will try to help. what is the make model and serial number of the sheer you have and do you have the specs on it for what it requires for pressures and flow to run? also what is the SN of your machine? How many lines do you have for the sheer?

Customer: replied 7 months ago.
The sheer has no branding, make or model on it at all. None. It is a sissor type sheer with one hydraulic cylinder that is 2", 1" bore rod with 8" stroke. The sheer requires 2 lines which I have as a aux on the skid steer. My machine is a 2000 Cat 226 serial # 5FZ03099

Thanks for the update. So it is just a double acting cylinder on the sheer. Verify the 3500 PSI is on the cutting side for the cylinder and the other is allowing the oil to go back to return. Sounds like either the AUX is not set right for this attachment where the return is not allowing the oil back to tank or check the piston seals in the cylinder for bypassing pressure or faulty relief which is unlikely if you are getting 3500 PSI and its not dropping off.

Customer: replied 7 months ago.
Ok. The 3,500 psi is going to the push/cut side of the cylinder. How would I check the cylinder seals? On the AUX hookups coming off the skid steer, is both lines supposed to be charged with 3,500 psi or just one of them?

Thanks for the update. Pressure test the cylinder deadheaded one direction with shop air is the least messy ans the safest. With the opposite port open you should have no leaks. One line is pressurized and the other becomes the return to tank to allow the cylinder to extend or retract. otherwise it will just compress the return oil and pressure will go to relief.

Customer: replied 7 months ago.
Ok. The cylinder tested good. I'm still not quite understanding my aux lines coming off the cat, when I pressure tested and pushed the toggle switch right one showed 3,500 and the other showed 0. Same gauge on, I push the toggle switch left and both lines show 0. Now those are the readings coming out of the aux lines off the skid steer. Is that testing correct? Or should the line showing 3,500 flip flop when I toggle right then left?

sounds like it is not set for double acting hydraulics and set for continuous flow. Let me do some checking

Customer: replied 7 months ago.
I talked with a CAT tech specialist at the closest dealership. He told me that my machine was not set up with continuous flow, he said if I wanted to run continuous flow that will just have to hold down one of the buttons that controls the AUX lines. That's about all he would tell me. I'm wondering and thinking, is it a problem in the joystick. Maybe like when I push the toggle one way that it is not sending the signal to the solenoid or control valve which wouldn't open the valve to open and give me the 3,500 psi on the other line?

3500 PSI is max these machines put out for Aux output so the problem is likely either in the control switches, wiring, or a solenoid problem not allowing two way function. Verify power to the hydraulic solenoid valves. 0 PSI the other way is likely due to a loss of power or ground to the solenoid or a faulty solenoid. Let me know

Dan and other Construction and Road Equipment Specialists are ready to help you
Customer: replied 7 months ago.
I will. I'm going to tilt the cab back and race all the lines looking for a problem. I will update you with what I find. Thanks
Customer: replied 7 months ago.
I have traced all my hoses and electrical lines going from the aux fittings down to the pump and joystick down to the pump. No obvious problems found. I checked all voltage to the solenoids and they read differently according to the buttons pushed on the joystick. I can send pictures of anything you would like.
Customer: replied 7 months ago.
The lines circles are the two lines that run from my front aux hook ups to under my cab. On the back side are to flexible hydraulic lines that run to another block. I will send a picture of that.
Customer: replied 7 months ago.
The lines circled here are the 2 flexible lines that run from the previous picture to a different block. The other circle are the two solenoids associated with the 2 flexible lines. I switched the plugs around and got the same pressure readings.
Customer: replied 7 months ago.
Ok in this picture the solenoids circled in orange. Well I've done some searching on line and found a diagram and it calls them both "Modulation Valve". Ok I unplugged them both, took the nut off the top and the pulled the top half off (which is the 3rd picture). I switched the top part of the valve with the number two valve and rechecked pressure. Still the same. After I removed the top circular part of the valve there was a stud still sticking out of the block (the stud is the lower half of the valve), it had a nut at the bottom of it keeping it attached to the block. I didn't have a deep enough socket to remove it. If I get a deeper socket should I remove the lower half of the valve and inspect it or swap it with the #2 valve? I'm not real sure what the modulation valve does, and what I will do if I remove, I just don't want to remove and have a spring come flying out and loose it. But my thinking is, these valves both go to the aux, they are both receiving power from the joystick, I'm getting good pressure on one of the aux lines but not the other, so it would have to be one of these modulation valves not opening to allow fluid flow thru.

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