Little bit shaky, Excavator

[MOOSE]

Wonder if someone can help, I have a Kato 900 excavator, that was running great, but then it started,
The movement of the machine began clattering, from the bucket the booms, the swing, all the way down to the final drives.

The engine runs perfect, the fluids are good & it just came out of the shop. The shop put a new control valve on one of the hydralic assembles. & returned it to the job.
Now the shop is telling me the main pump clyinders are bad. Both sides of the pump pistons?:beatsme
Whats your thoughts?
Thanks Ed:
Banghead

 

[Ross]

Wonder if someone can help, I have a Kato 900 excavator, that was running great, but then it started,
The movement of the machine began clattering, from the bucket the booms, the swing, all the way down to the final drives.

Sorry but we need a little more info than that mate.

Now the shop is telling me the main pump clyinders are bad. Both sides of the pump pistons?

How do they know that then? Did they strip the pump out during the shop visit?

Ross

 

[MOOSE]

Hi Ross,

Al ittle more info, when you attempt to track, swing the boom, move the bucket, dig, the machines hydralic lines shake, the machine clatters & is unresponsive. The machine has no power, but the engine runs great.
What do you think the problem is?::beatsme

 

[Wulf]

Moose,
It's a bit confusing, you said it was running great but then the problem started... but then your guys had replaced the control valve?
When and why did your guys replace the control valve? before the problem arose or after... when was it last running OK

Your description sounds like there could be a restriction in the suction line and the pump is starving for oil, also if some major work was done on the machine maybe they mixed up a load sensing signal line or a connector and the pumps are not being controlled correctly in relation to their demand.

 

[Ross]

Sounds like there's air in the system and the pumps cavitating.

Like the other posts. Restriction in the suction circuit maybe?

Signal problems also sounds viable as the pump must be tilting back off if your loosing the hydraulics at full chant. This doens't explain why the machine is shaking violently thou.

Main pump Piston/Sleeve defects Dont normally result in violent shaking either. Just loss of performance.

My moneys on a Rubber/latex glove in the hydraulic tank.

It's a bit confusing, you said it was running great but then the problem started... but then your guys had replaced the control valve?
When and why did your guys replace the control valve? before the problem arose or after... when was it last running OK

Yeah can you clear this up for us thanks?

Ross

 

[MOOSE]

Hey guys thanks for the responses. I'm in agreement with you.
The repair shop thinks it's the pump $$$$ maybe because they want to sell me something new:
But to me it acting as if it starved for hydralic fluid & the shaking is from the pump trying to suck & presurise the lines.
I thought about air in the lines, but under a presurized system would the oil be blowing out instead of sucking air in.

 

[thejdman04]

Hey guys thanks for the responses. I'm in agreement with you.
The repair shop thinks it's the pump $$$$ maybe because they want to sell me something new:
But to me it acting as if it starved for hydralic fluid & the shaking is from the pump trying to suck & presurise the lines.
I thought about air in the lines, but under a presurized system would the oil be blowing out instead of sucking air in.

It will suck wahtever it can be it air or oil. The chattering comes because air is compressable, fluids are not ( persay). The hoses and everythign shake and vibrate because it may get oil pressurize, and then sucks some air and pressure goes off.

 

[Dwan Hall]

Hey guys thanks for the responses. I'm in agreement with you.
The repair shop thinks it's the pump $$$$ maybe because they want to sell me something new:
But to me it acting as if it starved for hydralic fluid & the shaking is from the pump trying to suck & presurise the lines.
I thought about air in the lines, but under a presurized system would the oil be blowing out instead of sucking air in.

Make a deal with the repair shop. If they replace the pump and it fixes the problem then you will pay the bill but if it does not fix it then they eat the costs. You will have to oversee the repair to make sure they don't recover the laytex glove when replacing the pump. If they go for it then They may know what they are talking about but if they back down then they will just keep replacing parts at your expence till the problem is solved.

Does the shaking exist at idle?
and did the shaking start after the last service?

 

[MOOSE]

The shaking of the hydralics existed before it was serviced, they replaced a control valve, $1,500 & labor/ trucking & returned the piece of equipment. When the equipment was returned it ran fine for about an hour, but graudually the problem re appeared, to where the machine was acting like it did before the first service.
So I figure if it was the pump the problem would of never went away the first time. I think its a filter in the main tank.
Shaking exist at all speeds.
Thanks Moose

 

[LowBoy]

The shaking of the hydralics existed before it was serviced, they replaced a control valve, $1,500 & labor/ trucking & returned the piece of equipment. When the equipment was returned it ran fine for about an hour, but graudually the problem re appeared, to where the machine was acting like it did before the first service.
So I figure if it was the pump the problem would of never went away the first time. I think its a filter in the main tank.
Shaking exist at all speeds.
Thanks Moose

I'm leaning towards a restriction theory myself. If it were me, the first place I'd investigate would be at the bottom of the hydraulic reservoir, then to the next filter housing and so on. The latex glove theory sounds plausable. You'd be surprised what a small interruption in supply will do.

I had purchased a used (but excellent shape,) fuel oil delivery truck a couple yrs. ago. Worked fine for about 6 hours, then the pump started to cavitate violently, and wouldn't deliver any fluid anymore. I took it home, drained off the residual fuel in the lines, and started the hunt. At the strainer housing, I found a very unusual object...the last "so-called" mechanic's CELLPHONE in the strainer. I wish it still worked, I wanted to call him on it and tell him what an idiot he was, but it wouldn't power up.:cool2

Don't let the $100.00/per hour shop rate wolves get you just yet, hold off and do a little research before you give in to that.

 

[Xcopterdoc]

On piston pumps the one and only way to know if they are good or not, is to do a case drain test, BY THE BOOK and see if it meets the factory specs.
Perform cycle times to see if the pump flow is corrrect.
Perform system pressure check.
Very easy, cut and dry.
I would ask them what the case drain test revealed and what did the cycle times look like. I won't change a pump unless those 2 specs are out of tolerance.

 

[MOOSE]

Around & around we go

On piston pumps the one and only way to know if they are good or not, is to do a case drain test, BY THE BOOK and see if it meets the factory specs.
Perform cycle times to see if the pump flow is corrrect.
Perform system pressure check.
Very easy, cut and dry.
I would ask them what the case drain test revealed and what did the cycle times look like. I won't change a pump unless those 2 specs are out of tolerance.

Hi again, Well it's positive according o the shop it's the pump, yap, hope we can get a rebuild part, yap.
Well anyways, now that I have a new $2000 part from the first repair I didn't need, we might as well keep rebuilding.

But anyways, back to your reponse, hmmm sounds intresting. So tell me what is a case drain test.
As to pump flow , OK
But to the pressure check they say they did that & one side of the pump needs to be repaired / or replaced, but wouldn't that test be flawed if the filter was clogged.

Thanks everyone for the help!

 

[big red machine]

hyd.

will the first thing they should do is change out all hyd. filters, then do the case drain test on the pump, then a flow test on the pumps if they pass the case drain test. oh and one more thing a piston style pump cavitating is a death sentence it will pull the pistons off of the slippers and then its over and the whole hyd system will be full of debri.

 

[Countryboy]

Welcome to HEF big red machine! :drinkup

 

[big red machine]

Thanks

Thanks glad to be here

 

[Wulf]

Just a thought guys but how easy is it to test the pump case drain on a Kato excavator on the machine and what is the spec?

Checking individual track cycle times and system pressure is simple and will give you a very good indication of pump condition (flow and pressure) when the symptoms are so pronounced.

Firstly though, I would also take a really close look inside the tank, see whether the oil is aerated as it goes back in the tank, pull out the suction strainer, high pressure strainers (if fitted) and take a peek inside the tank filters.

I don't know Kato very well (ok... so not at all really) so if you have a digital camera I would like to see pictures of the machine and the pump set up if possible.

 

[Xcopterdoc]

A case drain check will determine if there is "blow by" in the pump. Any fluid that by passes in the cylinders of the piston pump ends up in the case and is drained out and back to tank. A little is normal and is needed, excessive amounts are counted as drips per minute or as a volume, as in cc's/ounces per minute or hour.
A pump produces flow. Pressure is resistance to flow. System and circuit pressures are controlled by relief valves. Excessive pressure in the return line before the filter would indicate a restricted filter. A pump that cavitates would indicate a lack of flow on the suction side of the pump from the tank.
Where it's all coming from is matter to be determined by the mechanic and how good he understands the simplicity of the system.
If they are going by pressures only, then they have incorrectly diagnosed your problem.