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Troubleshoot excavator not tracking straight. Yanmar VIO 50

jrhook111

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Sep 26, 2022
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41
Location
Virginia
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Farmer
Hi folks. I have a 2003 Yanmar Vio 50 and the left track goes slow. I've checked the track tension and they are not too tight. The controls seem to be adjusted properly, with the spool valve having equal travel on both sides, but that is just by me visually inspecting the valves movement. I should mention that I did a recent rebuild of the swivel joint for a different problem, but the tracking issue did not change with the swivel rebuild. I'm thinking the travel motor may need a rebuild, but how do I test it to know for sure? Also, anything else I should be checking? Thanks guys.
 

uffex

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Good day
A common issue with the small machines is often the pedal is obstructed or when cable operated is not adjusted so good. See attched forr more tips.
Kind regards
Uffex
 

Attachments

  • FAR Straight Crawling .pdf
    1.4 MB · Views: 15
Joined
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Messages
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Location
Green Bay Wisconsin
I’m curious to see what you figure out, there’s a guy on utube with the same machine and same issue that also already went threw the swivel joint because of a issue with the back fill blade. I’m no expert but I was assuming the swivel would have been the issue.
 

Yanmar Vio 50.2

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Apr 22, 2023
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2
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Burks Falls, Ontario, Canada
Hi folks. I have a 2003 Yanmar Vio 50 and the left track goes slow. I've checked the track tension and they are not too tight. The controls seem to be adjusted properly, with the spool valve having equal travel on both sides, but that is just by me visually inspecting the valves movement. I should mention that I did a recent rebuild of the swivel joint for a different problem, but the tracking issue did not change with the swivel rebuild. I'm thinking the travel motor may need a rebuild, but how do I test it to know for sure? Also, anything else I should be checking? Thanks guys.
A friend had a similiar issue, he switched the lines for the drives at the pump to see if the problem duplicated to the other side, This told him the drive was in need of rebuild on the bad side, but, he decided to do both at the same time. What it did so, is gave him the problem answer.
 

uffex

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Good day
Additional information that my help, the link is for a large file much applies to smaller machines.
Kind regards
Uffex
 

Attachments

  • Crawler pressure check.pdf
    840.3 KB · Views: 7
  • H2 Crawler issue check list..pdf
    1.2 MB · Views: 8

jrhook111

Active Member
Joined
Sep 26, 2022
Messages
41
Location
Virginia
Occupation
Farmer
I’m curious to see what you figure out, there’s a guy on utube with the same machine and same issue that also already went threw the swivel joint because of a issue with the back fill blade. I’m no expert but I was assuming the swivel would have been the issue.
Hey BP. Is your youtuber also named Jon? Yep, that's me.
 

jrhook111

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Sep 26, 2022
Messages
41
Location
Virginia
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Farmer
Good day
Additional information that my help, the link is for a large file much applies to smaller machines.
Kind regards
Uffex
Hi Uffex. Thanks for the additional info. I finally got around to testing this trackingh today, and was going to swap the hoses to see if the problem moved to the other side, only to find that the hoses aren't long enough to reach. Can't even do the swap at the swivel joint, no slack at all. It would probably be possible to swap them at the control valves, but that would be a major job in itself. I'm thinking I may just rebuild the travel motor on that side and see if that fixes it. Probably less work than doing the hose swap.
I can add that the left track is always slow, in both forward and reverse, and in both hi & low speed. It is also weak compared to the right. I've checked the pressure at both piston pumps and they are dead on at 3550 PSI. I am also having a new problem with the machine where the gear pump is failing (posted in a different thread), but the tracking started long before the gear pump issue, and hasn't changed at all.
Now I get to see how much a rebuild kit costs...
 

jrhook111

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Virginia
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Farmer
So, here's an update. I was going to price a rebuild kit and just do the rebuild, but they don't sell a rebuild kit for my travel motor. The dealer gave me a price on all the internal seals at $1000. I checked with aftermarket companies and nobody sold parts but just wanted to sell the whole drive, the cheapest I found was $2500. Dealer price for this drive is $5500. So suddenly it became worth it to be 100% sure of the diagnosis. I ordered some hoses so that I could switch sides and...it's a darn good thing I did, because the problem switched sides too. It's not the travel motor...and I was totally convinced it was. Phew!

I've already checked the output pressure of both piston pumps, and they are 3550 where they should be. The controls for travel are directly actuating the valve spools, so I think the problem must be in the control valve. Anything else I'm missing?

And then, I've never worked on a bidirectional control valve. Is it something I can rebuild without taking the whole valve block off of the machine? That would be a LOT of hoses... Advice appreciated.
 

uffex

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Good day
I suggest you make the check attched before you jump into the main valve.
Kind regards
Uffex
 

Attachments

  • H2 Testing Centre Passage.pdf
    1.5 MB · Views: 11

jrhook111

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Virginia
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Farmer
Thanks Uffex. Recall that I had this tracking problem prior to rebuilding the swivel joint, and no change in tracking symptoms after the swivel joint rebuild. (Repair of the swivel joint did fix the blade cylinder drift issue.) I'm pretty confident that it is not the swivel joint. That said, I don't have fittings to do the testing you suggest, but I can go buy some if really necessary.

I'm thinking pulling the spool out of the control valve might be the easiest course of action at this point. But it looks like there aren't any internal replaceable seals from what I can tell. Maybe I would find damage on the spool and could replace that (if I'm lucky), or if there is damage on the valve body would have to replace the whole valve. Is my thinking correct?
 

uffex

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Good day Jr
There are no seals in the spool slice, it is less probable that other that replace there is little to be done. The last post describes checking the main line pressures. You can do this by simply plugging the main line's from the slice with a pressure gauge. Run it up to temperature and check the pressure. Shut the engine down to idle speed while holding the spool in the opretive position. Observe on the gauge how quickly the pressure disappears towards zero on both main lines. If it sinks quickly means your spool - slice is leaking pressure, it gives a very good idea of the spool - slice condition. Keep in mind that seals in the central joint can still be where the problem is at.
Kind regards
Uffex
 

heymccall

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Western Pennsylvania
Wouldn't blocking the track and measuring case drain volume on each side stalled be more prudent if the travel motor is suspect?

Or, assuming you have caps and plugs, switch the motors side to side to verify the issue, since the hoses can't be swapped?

But, I'd case drain test first.
 

jrhook111

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Virginia
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Wouldn't blocking the track and measuring case drain volume on each side stalled be more prudent if the travel motor is suspect?

Or, assuming you have caps and plugs, switch the motors side to side to verify the issue, since the hoses can't be swapped?

But, I'd case drain test first.
Heymccall, just want to clarify that I did buy extension hoses and ruled out the travel motors as the problem, because when the hoses were switched the lazy track symptom also switched.

At this point it's gotta be the control valve or the swivel. Since the swivel was recently rebuilt with no change in this symptom, I'm leaning heavily toward the control valve. I'm going to do some tinkering and testing and I'll let you guys know what I find. Thanks.
 

Bibendum

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Canada
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This is quite timely as I have a 2006 Vio27 with near the same issue. I had an issue with blade down pressure and weak travel motors. I tested and found the joint bypassing, so removed and re sealed it. The blade works great now, and there was some improvement in the strength of the travel motors but it just doesn’t chug along like I’d expect it to.

I removed the case drain lines for each motor and check the stalled bypass through the entire rotation of the motor (or where I could lock it up/index it on the sprocket) The service manual does not give an expected flow rate, but after stalling the motor for 1 minute I have maybe a liter of fluid. Both motors bypass about the same amount. I am no pump guy, but this seems ok to me? Please correct me if I’m wrong.

I’ve re sealed and set the system reliefs to 2900lbs as the book specs out. I have not measured pump pressure, however I would be lead to believe that if the system reliefs operate as they should then the pump would not be the issue? Once again, please correct me if that is the wrong assumption to make.

The symptoms I have are weak travel, an inability to track up a hill at high speed (as in, high speed selection makes no difference when traversing up a hill) and the boom will not pitch the machine all the way back without help from other functions.

The boom, bucket and left side travel motor are supplied from P1, the other functions from P2.

I am starting to lean towards the main control valve which splits the valve bank. Both travel slices are on either side of the main control valve slice, and run off of the system reliefs. I have plenty of pressure, but I seem to lack flow? However in my head, if I lacked flow I wouldn’t be able to make pressure. Again, please correct me in this respect too.

Long winded but hopefully someone may have a bit of insight.
 

jrhook111

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Update. I cobbled together a test rig, but the results are less obvious than I was expecting. I determined the hoses that are pressurized for forward travel on both control valves, (it turns out it is the most forward hose on that valve.) I removed them at the upper swivel and capped the swivel connections and put a test gauge on each hose, hoping to do the leakage test Uffex recommended. So the valve hoses dead end in my pressure gauges. I then put both travel controls forward and move the throttle from full to idle, watching for how fast it leaks down. Here's the problem. There's only 200 PSI difference between high speed and engine idle, so there's not much movement on the gauge. When I go from high speed to idle, both sides drop pretty quickly, but I _THINK_ the left side (bad side) drops faster. If I kill the engine both immediately go to 0. If the valve would stay in the travel forward position when the engine is killed I would be able to watch it bleed down over several seconds and get a much more reliable result, but killing the engine immediately drains everything to tank, so can't do that.

However, I may have a result yet. When in low idle, the left (bad) side does something a bit odd. The pressure gauge bounces around between 0 and 3500ish, pretty fast. I would guess twice per second. The right side (good) doesn't do that. My theory is that at low idle the flow is low enough that I'm able to "see" the leakage...maybe? It's like it builds to a certain pressure and then it leaks and the pressure drops rapidly, then it builds again, and just cycles like that. The right side pressurizes and then stays stable. So does this count as a definitive result?

Your input is much appreciated.
 

Bibendum

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805033C9-29D9-4038-808D-42C6D042E61F.jpegJrhook perhaps this could indicate a leak on this section of the valve? May be worth pulling the spool and seeing what it looks like. The farthest passages on either side go back to tank.
 

jrhook111

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View attachment 285525Jrhook perhaps this could indicate a leak on this section of the valve? May be worth pulling the spool and seeing what it looks like. The farthest passages on either side go back to tank.
Thanks Bibendum. I was thinking of pulling the spool and taking a look, but will need to drain the tank for that. If there's a way to make my test more definitive it would be nice, so I'm hoping one of these pros on here will give me a tip before I go that route.
 

Bibendum

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Thanks Bibendum. I was thinking of pulling the spool and taking a look, but will need to drain the tank for that. If there's a way to make my test more definitive it would be nice, so I'm hoping one of these pros on here will give me a tip before I go that route.
May be able to put the tank under vacuum?
 

jrhook111

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Ok, so I pulled the spool and really didn't see anything wrong. I measured it with a micrometer in multiple places and it was consistent at 0.498". Actually 0.4985-0.4987 throughout. Minimal scratches under magnification. So I pulled the spool for the good valve and it measured and looked the same. I tried to look inside the valve body but can't really see. So nothing definitive.

Then I had a eureka moment. There are 4 possible causes, the pump(s), the control valves, the swivel, or the travel motors. I've checked pressures at the pump and they are good. I swapped the hoses at the travel motors and the problem switched sides, so motors are ruled out. It's either the valve or the swivel. Well now, all I have to do is swap the connections between the valve and the swivel. If it changes sides then it's the swivel. If it doesn't, it's the valve. Gotta be. And I'm already halfway there because I have the hoses disconnected from the swivel for my previous pressure test.

When I get a chance to do this last test, I'll report back.
 

jrhook111

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41
Location
Virginia
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Farmer
This is quite timely as I have a 2006 Vio27 with near the same issue. I had an issue with blade down pressure and weak travel motors. I tested and found the joint bypassing, so removed and re sealed it. The blade works great now, and there was some improvement in the strength of the travel motors but it just doesn’t chug along like I’d expect it to.

I removed the case drain lines for each motor and check the stalled bypass through the entire rotation of the motor (or where I could lock it up/index it on the sprocket) The service manual does not give an expected flow rate, but after stalling the motor for 1 minute I have maybe a liter of fluid. Both motors bypass about the same amount. I am no pump guy, but this seems ok to me? Please correct me if I’m wrong.

I’ve re sealed and set the system reliefs to 2900lbs as the book specs out. I have not measured pump pressure, however I would be lead to believe that if the system reliefs operate as they should then the pump would not be the issue? Once again, please correct me if that is the wrong assumption to make.

The symptoms I have are weak travel, an inability to track up a hill at high speed (as in, high speed selection makes no difference when traversing up a hill) and the boom will not pitch the machine all the way back without help from other functions.

The boom, bucket and left side travel motor are supplied from P1, the other functions from P2.

I am starting to lean towards the main control valve which splits the valve bank. Both travel slices are on either side of the main control valve slice, and run off of the system reliefs. I have plenty of pressure, but I seem to lack flow? However in my head, if I lacked flow I wouldn’t be able to make pressure. Again, please correct me in this respect too.

Long winded but hopefully someone may have a bit of insight.
Hey Bib,

I'm no expert but I'll give you my thoughts. First off, the top speed on these motors is pretty slow. Mine is 2.5mph I think. You might measure out a distance and time yourself on flat ground to see how close to spec your speed is.

I'm not a pump guy either, so I don't know if a liter is reasonable, but that sounds decent to me.

How did you set the system reliefs if you haven't pressure tested? (I'm a farmer not a hydraulic mechanic, serious question.)

It sounds like your travel is equal on both sides? Pretty unlikely that both motors are getting equally weak the same amount, or both valves are leaking the same... Or both P1 and P2 being equally weak. Seems odd to me.

If I were you, I'd want to have 2 gauges, one on each piston pump, and see how much pressure you are getting as you travel. Or just do one at a time with 1 gauge. I suppose if the pumps had internal leakage, they could generate enough flow to reach a high pressure, but with the travel motors in operation the pumps might not be able to make enough flow to keep the pressure reasonable. If that makes sense. My system relief is 3555PSI, so when traveling in low speed I run at about 2500PSI, and at high speed about 3400.
 
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