Yanmar VIO70 Boom won't raise

[fast_st]

Well not exactly but that's when I'm having a problem.

First thanks to the HEF gods, I was thinking about therapy while hef was offline but we're all good after the updates.

Yanmar Midi, pilot controls stacking a burning pile of brush, all functions normal, took a 10 min break and
on startup, could not raise the boom, cycled the safety switch on the armrest and ignition, no luck. All other
function seem to work normally, swing, bucket, dipper, thumb, boom down but just not boom up.

When the stick is drawn back there is a slight pitch change in the engine, like its taking a load but no movement.
Use the blade and dipper to jack up the front end and try again, still no motion of raising the boom. Boom cylinder
seems fine, works with the lines swapped. Removed and cleaned the lowering load check valve, nothing amiss was
found.

Tried swapping the pilot lines with the bucket curl right next position, was able to get one function swapped, lowering
and that operated with the bucket curl then raise suddenly started working. Put the lines back into proper places and
everything was dandy. Went out for another 45 mins or so and in the middle of a cycle, boom raise became
unresponsive again.

Looking at the service book but haven't seen a pressure spec. Need a BSPP to NPT adapter to toss a gauge on it. The
boom valve is the only double wide valve on the block. This seems pretty normal looking at valve blocks.

I think my next test is just to disconnect both up and down pilot functions and see if they flow about the same.

 

[Ma_earthmover]

Tried swapping the pilot lines with the bucket curl right next position, was able to get one function swapped, lowering
and that operated with the bucket curl then raise suddenly started working.
.

Would u give me more information about what do u mean in here , forgive my english but I did not undestand phrases such us "the bucket curl right next position" and the steps that u followed on these specific actions

 

[fast_st]

So looking at the valve stack that's under the floor hatch, the layout of the components from the outside toward the inside are as follows
return line-end cap, bucket curl section valve, boom section valve, left track motor valve, supply from P2 pump and so on all bolted together.

The track is mechanical control where the joystick functions are run by small pilot hydraulic lines. My thought was to see if the malfunction
followed the pilot control swapping the bucket curl for the boom function ports.

 

[heymccall]

Is there a boom overload pressure valve/ switch? It would be near the barrel plumbing of the boom cylinder.
My TB180FR machines (only the later serial numbers) have one.

 

[fast_st]

Is there a boom overload pressure valve/ switch? It would be near the barrel plumbing of the boom cylinder.
My TB180FR machines (only the later serial numbers) have one.

Nothing on the cylinder itself, the first time it happened I thought it might be the rebuilt cylinder so swapped the two hoses and was able to raise but not lower the boom, good enough to get it back out of the woods.

 

[Vetech63]

The rebuilt cylinder may be a clue here. Who rebuilt it? What condition was the old packing? It sounds like you have floating contamination in the circuit

 

[fast_st]

The rebuilt cylinder may be a clue here. Who rebuilt it? What condition was the old packing? It sounds like you have floating contamination in the circuit

I was thinking that, its a local builder / rebuilder, they've been in business a long time and really put out first quality work. Swapping the hoses on the cylinder showed the cylinder could physically function as needed. All the fluid was changed and flushed a while back, cleaned everything out while doing hose/cooler changes and fixing the AC. The odd part, after tinkering everything started working and worked well for an hour then quit again. I don't think its a pump issue as all the other functions seem to work at full speed like normal even in combination.

As to the old packing, the piston packing was in good shape but the rod seal had a nick that was allowing a bit of a leak under low pressure or at rest, once warmed up it seemed fine but don't like drips at $$$ per pail.

 

[fast_st]

I'm trying to scare up a couple BSPP to npt adapters to run some pressure checks on the pilot circuit, the service manual doesn't seem to say what the pressure numbers should be It seems to be variable pressure or flow to regulate the speed of the circuit selected.

 

[fast_st]

Well, opted to try another test, swapping the pilot lines at the control stick, down function works in place of up and no love in the other direction, started pulling and capping a few lines today. Any one have experience in pulling two valves from an excavator stack without disturbing the rest of the group?

 

[fast_st]

So the book doesn't have a lot of troubleshooting steps, pilot pressure looked good, right around 400 psi, tried swapping the pilot lines at the joystick, same behavior. Drained the hydraulic tank, removed and capped a bunch of lines, loosened the valve block and removed the return section, bucket curl section and boom lift section. Dismantled the valve and found the spool was stuck, it would move in the the lower direction but not raise, actually both movements were far from smooth. The sliding spool is a lapped fit to the valve so would require a new $3k valve section for official repair. There was also a sliver of metal, looked like a piece of internal thread that was recovered from inside the valve.

The edges on the spool were sharp and a look under a lab microscope showed a few raised sections. Using an arkansas oil stone, white I was able to polish down all the high spots using the oil film to hilight all the high spots, it would show a deviation in reflection. With careful polishing and constant inspection under the microscope all the raised areas were knocked down.

On reassembly the spool slid right into the bore and the section orings were replaced and oil was filtered before putting it back in the machine, a run test showed no external leaks and operation was normal for the boom, nice and smooth. Dismantling the valve block wasn't needed but I had no idea what I was doing and it did allow me to find that sliver of metal, seemed to be cast iron. All fixed and back working again.

 

[fast_st]

Everything still working perfectly! time for a oil change

 

[rob fong]

nice work. my sv100 the left travel spool seems "gummed" up. Maybe ill inspect the spool

 

[fast_st]

nice work. my sv100 the left travel spool seems "gummed" up. Maybe ill inspect the spool

I think the travel is linkage driven versus pilot hydraulic. There are grease fittings under the floor to lube up the pivots. You might be able to reach them from the front!

 

[rob fong]

I think the travel is linkage driven versus pilot hydraulic. There are grease fittings under the floor to lube up the pivots. You might be able to reach them from the front!

Yeah they are pivotting fine. It feels to me really like an o ring could be jammed up in there or something. You push the travel lever forward and the track barely crawls, work it back and forth a few times and then it moves full speed with full power. I'll test pressures etc. before tearing in to anything. Thanks for response. vio70 and sv100 really similar models I believe.

 

[fast_st]

Yeah they are pivotting fine. It feels to me really like an o ring could be jammed up in there or something. You push the travel lever forward and the track barely crawls, work it back and forth a few times and then it moves full speed with full power. I'll test pressures etc. before tearing in to anything. Thanks for response. vio70 and sv100 really similar models I believe.

If the valve moves full stroke and you don't get much crawl, it could be something different. If you go both full forward / reverse does it track straight or just move slow? Does hot or cold matter?

 

[rob fong]

If the valve moves full stroke and you don't get much crawl, it could be something different. If you go both full forward / reverse does it track straight or just move slow? Does hot or cold matter?

Yep going both full it always works properly. the issue only arrises when using just the left. What do you think? Swivel joint?

 

[fast_st]

I don 't have my service manual but I'd look into the functions that run on the same pump as the left track. Maybe its not stroking when the track function is called. Have you pulled the floor pan to watch the linkage etc? Not sure if its the same as the VIO70 but should be close.

 

[rob fong]

Will look into that, thank you. Yes linkage is moving fine.

 

[rob fong]

I don 't have my service manual but I'd look into the functions that run on the same pump as the left track. Maybe its not stroking when the track function is called. Have you pulled the floor pan to watch the linkage etc? Not sure if its the same as the VIO70 but should be close.

Hey so get this, I think the left track and aux are near each other on the stack. The problem seems to be gone from the left track, and now my thumb will only close, not open. When I operate the valve to open the thumb, the motor bogs down some. I think there's a piece just like you had, and it moved to that valve. So can I leave the valves installed and remove the spool in the field? Thanks

 

[fast_st]

So that's curious, my track is linkage driven, the boom is pilot controlled and the pilot couldn't force the spool one way but it would move the other. You might have some big chunk of debris wandering around. I'm wondering if you could get a chunk of hose into a bucket or pull the non moving circuit off the thumb and see what shoots out!