D6r iii. Operator lowered blade. Quick drop activated as normal. Cant lift blade. Very little action on blade cylinders. Other functions are normal. No leaks. Fluid level up. By putting lever in hoist we were able to lift blade using excavator. In nuetral position blade is locked so that excavator wont lift it. However, in nuetral blade still drops. It seems like quick drop valve is hung up. Help! Ken
Pull the quick drop valves off both lift cylinders and strip them. It's likely the spool I one or both has something jamming it. The valves are not complicated.
Could also be a piston bypass valve. Or a blown packing or bolt backed off in a cylinder.
I should have asked if when you try to raise the blade do the hoses to the lift cylinders show obvious signs of pressure in them. They should go as rigid as an iron bar if you give it full control lever movement with the engine at High Idle. If you can't see any signs of pressure in the hoses then you need to be looking at the control valve rather than the lift cylinders. When you say "Other functions are normal" I assume that includes the blade tilt function, correct..?
Took a while to figure oit how to remove the spool but nige was bang on. Cant upload pic but we pulled a small handfull of what looks exactly like metal drillings. Full helixes and a bunch of them all packed tightly in one gallery in the valve body. Looks like sabotage for sure but not sure how they got to that spot. Will cut filters and sample oil. Will post pic when i can
Even a blind squirrel stumbles across an acorn every once in a while ....... Depending on how old the machine is those drillings could have been there since it was built. I've lost count of the number of mining machines I've put together on site over the years and found drilling/machining swarf in passages while we were hooking up hoses or making all sorts of other connections. That was just what we could see, stuff that was buried in the dark corner of a casting somewhere could take years to move. While sabotage is still a possibility I'd suspect it was most likely something that was not properly cleaned out at machine assembly.
Without seeing the stuff this is just a shot in the dark, but the debris you're describing sounds like what you find when the piston has been galling on the cylinder wall. Is the rod bent by any chance?
We pulled this metal out of the gallery around the valve quick drop spool. The gallery is connected to the lower end of the lift cylinders. Reassembled and tested, but the tractor didn't run a minute before it began acting up again. We pulled off one cylinder an will open it up tomorrow. Hard to believe cylinder piston can create this sort of shards but time will tell. Have to open up the quick drop valve again before retesting.
Can you post a better close-up photo of the particles..?
I had a 740 that got a rock jammed behind one of the hoist cylinders and bent it. It put swarf just like that through the whole system.
That metal looks sharp to me. If it was sabotage, they probably took off the cap and dumped it in, right? Take a magnet on a stick, or even a clean rag on a stick, and fish around the bottom of the tank. Is there a suction screen on this machine?
Ain't no way that's gonna make it through a pump, a spool valve, and get caught up on the cylinder end of a manifold block, just my opinion. As Cmark sez, looks like the piston shredding the barrel wall like a hand plane curling up wood off a nice hardwood plank.
trying to get a better pic Looking closely at the cylinder you can see it is a little tweeked. We were pushing a huge willow at the time, so its not hard to imagine how it got bent.
So what does the inside of the cylinder look like then..?
haven't got there yet. Couldn't get the rod nut off so had to take it to the man....
Cylinder shop called. Cylinder bore is scored 80% of its length, but not so deep. They are sending it out to another shop to hone it. Hopefully can save the bore. Same goes for rod. Its barely bent, so they figure straighten it. trees are hard on equipment.