Hello knowledgeable Heavy Equipment forum members. I have a Yanmar VIO2-2 excavator. All rams are operating fine with a solid hold apart from the blade. The blade is only drifting down, which expands the cylinder (spear exits cylinder). It does not drift in the opposite direction (spear enters cylinder) when the excavator is resting on blade, for example. There is only the weight of the blade expanding the cylinder, so relatively little load. If I raise the blade as high as it will go (cylinder fully retracted), it immediately starts drifting down as soon as the lever is let go at a rate of about 8mm/sec. When the lever is activated in the opposite direction, to drive blade down intentionally - it takes time for the hydraulic action to "catch up" with the drift. In other words, if the blade is raised as high as it will go, and left to "fall" to the ground, then the blade lever is activated in a downward direction - it takes the same amount of time for the blade to start lifting the excavator, as if the blade was still at the top. Momentarily there is no active movement of the blade, until the distance the blade has dropped has been taken up (by what?). I'm mechanically capable - and have no problem disassembling the valve bank/ram for the required repair. Just need some guidance on where the likely cause is of this problem. Thanks all for your time.
I also note that this has got worse over a time period of months - and speed of deterioration has increased as time has gone on.
I would suggest first to pull the blade lift cylinder off and disassemble it. My guess is that the piston seals are toast.
Thanks Nige. This is no problem to do. I've read various posts which tend to talk about the valve leaking as the likely culprit of cylinder drift - I was hoping the delay in cylinder response after drift would indicate presence of a vacuum in the system on the non-spear side of the circuit - so I was leaning toward piston seals as well. Machine has done 2800 relatively light hours. Any further perspectives/ideas appreciated. Thanks all.
Make that the entire circuit....!
Eliminate the easy stuff like piston seals first before moving on to pulling valves apart would be my suggestion.
Aaaaah, sounds pretty similar to the problem I have got, we are going to the centre rotary manifold joint as the right track is a bit lazy as well as the drooping blade, we suspect the seals have gone in the joint.
Good point, and if the OP had also complained about problems with track motors the swivel would have been the first thing I would have suggested. As it is I'm going to suggest to him that if the seals are good in the blade cylinder the next place to look at would be the centre swivel.
Thankyou Patrick M and Nige. There are no signs of track performance degradation and tracks do not "interact" with blade. I understand there can still be internal leaks which would lead to the drooping blade - it would be much more convenient to do piston seals! Will be attending to shortly and will post results. Thanks again.
Hi, yeah I know that they don't interact but they are both fed through the center rotating joint, I mentioned it because I have a problem with the right hand track and the blade operation and so the likely point would be the center joint for me to go to. I only mentioned it because it may be the quickest, easiest and cheapest way of curing the problem as it (in my case) does not take a lot of effort to dismantle and renew all the seals and end up by fixing any looming future problems at the same time. I watched on Utube a bloke rebuilding one for a Case machine (I think) and when he pulled it apart there was all sorts of broken and brittle o'rings inside the joint so he obviously rebuilt it and "Bob's your uncle" all for the cost of a few seals and a bit of energy. Sometimes we can over analyse problems with our equipment while the solution to it only needs the simplest of measures. hope you get it going ASAP Regards: Patrick M.