My case 580c seems to get weak after about 20-30 minutes of digging. I do have a 3 foot wide bucket and I have been digging a lot of heavy mud. But it gets to the point where I can hardly lift the bucket out of the hole. This is my first backhoe (never even ran another) so I have nothing to compare it to. So am I asking too much of it with the 3 foot bucket? Does a hydraulic pump that is worn get weak after warming up? Could it just be my filter? Thanks. Jeremy
First of all, what does your hyd oil look like? Is it clear looking oil? Or is it white/cloudy looking oil contaminated with water? Oil that has been emulsified with water is bad. The water can turn to steam in the pump at high oil temperatures. Second, a 3 foot bucket is pushing it on this machine's hydraulic system. The load produced by that large a bucket can cause oil temperature to increase, even with clean oil. When any hyd oil goes beyond a certain high temerature, it can "shear" in the hydraulic pump, which will destroy the pump over time. Work your machine until it begins to get weak, then place your hand on the hyd tank. If it "burns your hand", the oil is too hot. This could be because the hyd cooling of the machine can't handle the 3 ft bucket, but it can also be a pump that has a lot of wear. If the tank is still relativeley "cool", you could just have a worn pump or a relief valve that can't handle the 3 ft bucket.
The hyd oil looks clear. I will check the temp of the tank next time I run it (hopefully tomorrow). One thing with my backhoe is that it can not lift up the machine with the backhoe like many other machines I have seen. I have tried it in different positions and it can't do it. The stabs can if I do it one at a time. So that has had me questioning how good my pump is. Any idea how much a new pump costs?
It could also be the master relief valve on the hoe, they do go bad. I'd check that before I went after the pump. Run your machine until the hoe won't "pick a load", then roll your front bucket back until it deads the cylinders. If it loads the engine upon cylinder dead, I'd say your pump might be OK and you have a probem in the hoe relief circuit.
Jeremy: I would do as ATCO said warm machine until it will not pick it up. However I would try picking the front of the machine off the ground with the loader bucket make sure your stabalizers are raised up. Does it lift the machine? If it does pick it up hold it over relief for a few seconds and note the engine rpm, now release the lever. If the engine speed dropped about 100-150 rpm while stalling and it did lift it off the ground your main relief is likely OK and probably so is your pump. If it lifted the machine but slowly or did not drop engine speed I would check the main relief pressure. It only takes about 900-1000psi to actually lift the front end. The main relief is in the loader valve and is also the backhoe relief. If that all checks out I would say your problem is most likely a secondary relief or load check in the boom circuit. If you raise your boom does it drop to the ground? Quick way to test the load check extend the stick out all the way, raise the boom so the bucket is about 4 feet off the ground. Release the boom lever. Now feather the boom up, if it drops before it raises thats a bad load check.