OK- probably will seem like a stupid question. But here goes. I have a new Cat 307E2, Ser KC900982. Equipped from dealer with hyd quick coupler, and hydraulic thumb. When I received the machine, the thumb bottomed out in the bucket. After I mentioned thinking this wasn't correct, they changed the thumb to a longer one that does extend just past buckets' cutting edge. A handy device now. Question about relief pressure on thumb. It seems from my reading here over the years, that it is customary that the bucket curl will roll the thumb up as well. Mine usually won't. But nowhere in the manual can I find any reference to it or how to change it. Nothing in the electronics about an adjustment. Asking the sales person didn't get me a definite answer either. A) Should bucket roll the thumb up? B) If yes- how do I adjust the pressure relief to allow this?
Yes the bucket curl should over power the thumb (keeps from breaking the thumb cylinder. Where that relief setting is on the machine, I don't know, but Cat should set the thumb up correctly and setting the relief is an important part of that. I would talk with the service manager about setting the relief. It should not be your responsibility to set it and you have in my view already paid to have it done.
Thx for the feedback. Do wonder if the setting is user serviceable as in if I use that circuit for another device and need full prep- or would that ever be an issue? Don’t like the thought of having to have dealer adjust it every time.
You will need to locate your relief valve and hook a pressure gauge in line to measure and adjust. Best to make Cat fix their mistake, especially if you want a warranty.
The only time I have to mess with mine (Taki) is when putting a mulching head on the excavator. The lower psi rating to compensate for the thumb doesn't work for that as it needs max psi. When it comes to running a hammer or hoe pac, the thumb setting runs just fine, at least for me.
Do you see a block on the thumb cylinder where the hose/s connect to ? It might not even be a relief in general sense but counterbalance valve.
I've been dealing with a customer that bought a new Cat mini also that has a thumb and a wrist bucket on the same circuit, using only one or the other. The wrist bucket requires the relief set at 3500 psi which is much to high for the thumb, that's the way it came from Cat. I'm planning to put a relief block on the stick and relieving the thumb close side, dumping it to the thumb open line. I'm not to concerned about relieving the open side. To adjust the relief, follow the thumb lines back to the control valve, it will be the aux. section probably 3-4 sections back from the front of the valve. There will be 2 adjustable reliefs on the side facing out, one up top and one down below. Then you need to put a gauge on the control valve test port and adjust the pressure while closing the thumb.
Here is a picture of the valve. Each function has its own line relief. The thumb should be on the auxiliary valve Illustration 1 g03845061 Relief valve location (1) Main Control Valve (2) Swing motor (3) Pilot Relief Valve (4) Auxiliary Relief Valve (5) Auxiliary Relief Valve (6) Blade Relief Valve (Rod End) (7) Blade Relief Valve (Head End) (8) Stick Relief Valve (Head End) (9) Stick Relief Valve (Rod End) (10) Bucket Relief Valve (Head End) (11) Bucket Relief Valve (Rod End) (12) Boom Relief Valve (Rod End) (13) Boom Relief Valve (Head End) (14) Swing Relief Valve (Right) (15) Swing Relief Valve ( Number 7 on color pic is aux valve .
Thumb is usually around 2500 but dealer should have specs and they should adjust it. It should fold back when the bucket hits it although there may be some spots in the travel where the bucket is weaker. Fully dump position can cause lower mechanical advantage for the bucket.
All good info. Thanks. Flooding here, so not going out to look today. But- this machine has 2 Aux circuits. One has flat faced couplers and the thumb is pulled off of those lines right before the q/c. The second lines is another set of q/c. Would the valves for that be in the same bank, or somewhere else? I believe I've read where 1 set was standard, 2nd set optional. My hope in the future is to run a mulcher on the second set.
Now- I am an owner/operator, but pretty handy. But- have no gauges. Presume it isn't acceptable to lower the pressure (assume loosen adjusting screw) until proper operation is reached?