Track Speed Issues - Kobelco

[wgwestervelt]

I have a Kobelco SK150 MK IV that I recently acquired. I am new to the world of heavy equipment so bear with the stupid questions.
This machine has an issue with one track running slow - maybe 70% or so of the other track. This is a problem on both high and low track speeds.
At the advice of a friend I have checked for crimped lines, leaks, etc. and cant find any. Any other ideas other than replacing the track motor or how I can further troubleshoot?
I suspect the hydraulic fluid may be a bit low but have not topped off yet. Cant imagine this is it.
Thanks - love this forum. :notworthy

 

[cps]

It may well be your slew joint, this is the joint in the middle of the machine that the track motor pipes flow througth, the seals may be gone! This would be your cheapest way out!

You can do a simple check on the motors them selfs, remove the covers on the back (between the two tracks) and you ll see the pipes there should be three pipes two large one small, if you remove the small one and have someone in the cab to turn the track( with it of the ground) and see if there if any oil coming out of the motor, there should be a small amount not much, if there is a fair bit you have a problem in your motor!

Hope this helps

CPS

 

[wgwestervelt]

thanks CPS - can you explain the logic around the motor test (not sure what the small line is vs the larger lines). Would like to understand it.


If I crawl under the center of the machine and look up at the cylindrical unit that the pipes are distributed from - is that the slew joint? Is that where the access is to check it?

sorry for the basic questions - still getting aquainted with this machine......

 

[cps]

thanks CPS - can you explain the logic around the motor test (not sure what the small line is vs the larger lines). Would like to understand it.


If I crawl under the center of the machine and look up at the cylindrical unit that the pipes are distributed from - is that the slew joint?.

Sure thing, the two large lines at the motors are the travel direction pipes 1 forward 1 reverse as such!

The small line is whats called the case drain, this allows excess oil in the motor to drain back to the tank!

Like i say there should be a small amount (kobelco manual may give exact specs if you can get your hands on one) if there is a large amount the travel motor may be passing more oil than normal causing it to slow down!

But chances are it is more likely the slew joint, yes that is it, you can acess it from underneath aswell as above, both if you need to remove it! theres no real way of checking it, although seal wont be very expensive so most poeple pull it out and reseal it, you may find a bad seal when doing this!

Hope this is abit more understanding

CPS

 

[Chris5500]

Before we get too carried away, lets start with the not so obvious but easiest to rectify! Ensure there is nothing obstructing the travel pedal (Of the one corresponding to the slower side) and limiting its stroke (trap for young players ).

Next, check if the maximum pressure can be built up with other movements on the same control valve (Check the MRV pressure) - If the MRV pressure is down, even just a little, get it back to spec as this can have an adverse affect on other components and circuits. (This wont be the root cause).

Now check if the movement of the travel circuit spool(s) on the control valve is ok.

If the spool is ok (You can skip the last step and do this step 1st if you want, but if this step turns out to be ok then go back) check the pressure of the SRV and again, adjust as required (If there are 2 or more SRV's then the gauge will read the pressure of the one with the lowest setting)

Check the condition of the ACV for the travel circuit (If the machine has them)

If you find the above to be in spec or in serviceable condition then the probable faults are as follows:

1. Rotary joint (Internal leakage)
2. Hydraulic motor (Excessive wear between barrel/pistons casuing excessive leakage through the case drain)
3. Travel brake (Not fully released, released but deformed lamellas caused by overheating)

I think the above is pretty self explanitary to check and rectify, but before you go removing and resealing your rotary joint I would advise checking for leakage first.

Quite simple really (If the test fittings are installed), you will need 4 test gauges (And corresponding test fittings and test hoses)

1. Identify and A, B, C, and D ports on the rotary joint.
2. Connect the four gauges to the travel circuit.
3. Label the gauges as per the rotary joint labels, A, B, C, and D.
4. Apply Left and right hand sides, both forward and reverse individually and recorded pressures.

What you want is something like this:

A 123 Bar
B 0 Bar
C 0 Bar
D 0 Bar

What you dont want:

A 123 Bar
B 123 Bar
C 0 Bar
D 60 Bar

Let me know how you go!

 

[wgwestervelt]

Chris - Very helpful advice, thank you. I like the idea of getting some data before taking things apart.

I just got this machine and in the middle of getting the engine back together after repairing some minor oil leaks. Should have that done over the next couple of days.

I also just got the manual on it and have started working my way through the maintenance list and I am not so sure the most recent owner was particularly diligent. For starters, the hydraulic level is somewhere below the bottom of the sight glass and the swing motor level is below the bottom of the dipstick. Getting those trued up wont hurt things.

When I was messing with the track issue noticed that the handle/pedal arrangement in the cab had a lot more side to side play on the problem side vs. the other side. To me, this did not look like it had anything to do with the actuation of those valves (front and back movement) but I am not an expert on how that valve box is built. I was considering switching the lines there and seeing if that did anything.

More to come on this happy subject but it will be a few days until I am prepared to test out some theories.

Finding pressure gauges for those 25 mm or so lines here in the US might be a challenge........

Bill

 

[Chris5500]

When I was messing with the track issue noticed that the handle/pedal arrangement in the cab had a lot more side to side play on the problem side vs. the other side. To me, this did not look like it had anything to do with the actuation of those valves (front and back movement) but I am not an expert on how that valve box is built. I was considering switching the lines there and seeing if that did anything.

By all means, good thinking, very simple to do and something else to cross off the list. Its definitely not uncommon for the casting lands in control valves to hydraulically corrode causing pitted spools and/or casting lands which, in turn, will reduce the sealing of the valve. When the errosion reaches a critical size, a small orifice is created allowing oil under flow and pressure to bleed off from the pressure port to the tank port, and as such will result in poor performance (In your case, slower travel on one side than the other)

Which brings me to my next question

Is the side in question slower in both directions!?

Remember, troubleshooting is generally used to describe noninvasive methods to determine the cause of a fault.

 

[wgwestervelt]

The travel speed is reduced in both directions and at both high and low speeds......

 

[Chris5500]

Whats the latest buddy?

 

[wgwestervelt]

Whats the latest buddy?

i have been waiting for a gasket to get the engine going again. This machine was not well cared for before I bought it. When I went to change the oil, the oil drain plug was worn completely smooth. Shy of welding a bolt to it, there was no getting this off with conventional hand tools! So I dropped the oil pan and ordered a new plug and gasket. Will have this back together this weekend and will get back at this track issue Sunday - stay tuned! Bill

 

[Digger145]

When I went to change the oil, the oil drain plug was worn completely smooth. Shy of welding a bolt to it, there was no getting this off with conventional hand tools! So I dropped the oil pan and ordered a new plug and gasket.

For next time (or for others), vice grips with good teeth or better yet, a hammer and metal working chisel; just tap it around on the angle - then replace the oil drain plug.

Staying tuned. As my drive motors are getting slow too.

 

[wgwestervelt]

For next time (or for others), vice grips with good teeth or better yet, a hammer and metal working chisel; just tap it around on the angle - then replace the oil drain plug.

Staying tuned. As my drive motors are getting slow too.

well vice grips was not getting it done on the machine. This baby was stripped and tight.

What worked on the bench was heat, a pipe wrench and a pipe on the wrench. Then she came. Guess I could have tried all that on machine - next time!

 

[Caiwu]

Hi Chris5500, Hitachi excavator EX200-5,one side treak tread run faster so it will run to one side,If we repair it according to what you said on #5.What should we notice?
Thank you very much

 

[Chris5500]

Hello caiwu, I'm not quite sure as to what you mean by "what should we notice?" If you care to explain as to what you mean, I can try and answer your question

 

[Caiwu]

I mean please help me to troubleshoot the problem of Hitachi like you do for Kobelco on#5.Is the pressure the same?Is the test procesure ithe same?I have no service manual.
Thank you very much.

 

[Chris5500]

The procedure would be the same; it’s a generic one that can be used on any excavator to diagnose poor travel performance.

The pressure's I used for the rotary joint leakage test "123" are just an example to show the desired results (no leakage between ports), regardless of pressure. If you followed the earlier steps then the pressure at the rotary joint should be within specification as you would have set the MRV pressure, which I'm guessing would be up around the 300 bar mark. You wont need a service manual to do the above, but you will need specs for the relief pressures and some test gauges.

Hope this helps.

 

[Digger145]

You wont need a service manual to do the above, but you will need specs for the relief pressures and some test gauges.

Chris, if I wanted to get some gauges to do some DIY work on the farm digger, dozer, bobcat, you know... what should I be buying? 1 or more and a working range pressure ???

Cheers.

 

[Chris5500]

I use a variety of different stauff test equipment with Caterpillar and Komatsu test adapters. Depending on what type of equipment you have whether it be Caterpillar or Komatsu, will determine what adaptors you need to buy to fit the machine.

Probably your best bet would be to pay a visit to your local Pirtek branch and check out their range of stauff test equipment. I highly recommend the stauff brand, very good quality and compatibility. Off the top of my head I think the gauges are roughly $40-50.00 each for a gauge, regardless of pressure, and the test hoses are roughly $30-70.00 depending on the length you want.

What you want:

Stauff 63mm, stainless steel dual scale Bar/Psi glycerine filled, bottom entry test gauge.

Stauff test hose 1/4" Bsp gauge connection x 16mm x 2mm ‘Test 20’ Female Swivel w/ Dust caps both Ends.

For a general service set for the smaller equipment as you mentioned, you'd probably be only looking at one 400 bar gauge (for mains and secondary's) and a 60 bar gauge for pilot pressure. If you were really keen and thought it would be worthwhile you could get four 400 bar gauges for a rotary joint leakage test on your excavator.

Hope this helps

 

[Digger145]

....

What you want:

Stauff 63mm, stainless steel dual scale Bar/Psi glycerine filled, bottom entry test gauge.

Stauff test hose 1/4" Bsp gauge connection x 16mm x 2mm ‘Test 20’ Female Swivel w/ Dust caps both Ends.

For a general service set for the smaller equipment as you mentioned, you'd probably be only looking at one 400 bar gauge (for mains and secondary's) and a 60 bar gauge for pilot pressure. If you were really keen and thought it would be worthwhile you could get four 400 bar gauges for a rotary joint leakage test on your excavator.

Hope this helps

Thanks bud, the main animal is a SH145 Sumitomo 1996 (13 ton class) which must stay alive ATM, as it has the most punch.
It's due for service and has to track a 1km back to the 40 foot container (workshop). We try to spoil it when it comes in, even break out the MIG sometimes It's going to get new chains this time, so I might look at the slowness in the hydraulics also, yours & CPS tip's have been noted - thanks to both .

 

[wgwestervelt]

removing slew joint

OK guys, still plugging away on my track speed problem. Today I finished getting the motor in shape - no leaks and purrs like a kitten so i am psyched about that.

So then it was on to the track problem. Checked the motor on that side an no fluid comes out the drain line. So that does not seem to be the problem. Frankly I was considering living with it for a while but in evaluating the motor problem I have found a persistent leak at the top line of the slew joint which goes to that side but not enough to cause the problem. To really tighten this joint I found that you need to remove the two below it and by the time you have all three off you are rapidly draining most of the hydralic oil. I found out by accident that with the bottom line of the slew joint off you drain just about all of it.:Banghead

SO here I am with the hydraulics drianed and 3 of the lines off the slew anyway. I am figuring now just take off the damn thing and take it apart and check that off the list.

Anyone have any experience with the SK150 and how involved this is - basic steps, etc? Thanks - Bill