Been running a EC460B machine the last few days. An issue we have noticed is the arm is slow to retract. Extending out works like it should. Seems like if you try and go full speed in right away then it goes normal speed. But if you start out slow and want to speed up it won't do it. It will actually load the engine a little but it just seems like something is holding it back. We have had our Volvo tech out a few times trying to figure it out and even he is confused... Looking for any ideas!
I suspect you have a bound arm regeneration valve. I have attached the description of the main control valve so you can look for it if you want to pursue that. The second possibility would be the arm 2 spool which throws extra oil at the plus side of the arm cylinder to increase flow. Before looking into the hydraulic side, I would inspect the mechanical side. Check the rod, verify it isn't bowed or scarred from rubbing something. Second, Check hydraulic return filter. See if there is any debris, metal shavings, vinyl etc. I almost forgot, in the arm cylinder, there is a damper valve in the threaded end of the rod, behind the piston. It has been known to come apart from time to time. It could be blocking the oil flow, which could be what you are perceiving as loading the engine. If you have an infra-red temp gun, you could look for the hottest point in the circuit, that would give you an idea where to begin your search.
If it was a cylinder issue itself im guessing it would always be slow to retract? Extending has never gave any problem. The weird part is how when you start out full stick right away then it comes in normal speed. If you start out moving it slow sometimes you can actually feel the machine kinda jerk like something is holding it back. Our Volvo mechanic submitted this issue to Tech Support and they seem to think its an issue with the load holding valve...
That's the thing about floating debris. It's inconsistent. It gets shoved around does what it does. The snubber valve, you'll have to disassemble the cylinder to inspect. The same goes for the arm regeneration valve and the arm 2 spool. You won't know till you "get after it"
This machine recently got all new hydraulic fluid and filters. Didn't notice anything in the filters when I changed them.
Load holding valve only comes into play when pump pressure is below pressure needed to move load. That way, when you pull the lever, the load doesn't drop.
I will definitely pass this info onto him. Thanks!
The scary thing is, your dealer tech should know these things, unless he's an apprentice. Ask the service manager to provide a person who is proficient in excavator, Volvo excavators would be best. I would also ask for consideration regarding your last service call which amounted to a ,"I don't really know. "
So I talked to the tech who was out and gave him your thoughts. He said the load holding valves work on the return and pressure side and are activated by pilot pressure. When you move the lever to move the stick in, the same pilot pressure that goes to move the main spool also goes to the load holding valve to unseat it so the return oil can come out of the cylinder...
I'm gonna disagree for know, but I'm gonna research. I'm human and old, I could be wrong, but I don't think I am.
hi guys I think there is a communication problem with terminology here funwithfuel is talking about the load hold check valve inside the main control valve and it does exactly as he says I think Kevins guy is taking about the valve mounted to the cylinder if fitted which can be known by different names ie hose burst valve ,deadman valve, double lock valve, piloted operated check valve etc,etc,etc
This machine does not have that valve mounted on the cylinder. That must have been an option. I do know what your talking about because I seen it listed in the parts diagrams...
uploaded new mcv description, my apologies, I did not realize the other one was incomplete.
I've reviewed the materials, I stand by my statement. I have attached descriptions for both the load check and the arm regeneration valve. You can see how complicated the regen valve is. It would only take a bit of packing material floating around to impede travel or block a passage. Now, the arm in conflux description and illustration are included to help you understand all the voodoo that takes place when you pull the lever in hard for increased speed. It clearly explains how pump 2 comes in and joins pump 1 to increase flow for speed. Again , a cheapy infrared temp gun would be a helpful tool to help you find where to start looking. The hot spot gets attention. Wherever there is a restriction or opposition to flow, the heat will be higher. I don't want to get in a pi$$ing match w/ your dealer tech, I'm just trying to help you understand what he is supposed to be doing , what could be going on and what I've personally encountered as a Volvo tech over the years. I've given you the tools, it's up to you and your tech. If you choose to share the cause, we would all be grateful.
LOL.... You dam old timers!!!
Definitely no issue at all! I very much appreciate all of your help with these machines so far, you have been a huge help. You have a great amount of knowledge with these machines no doubt!
Hukt on fonix, werkt fer me Young whippersnappers