bobcat hydraulics problem

[firewood]

Ihave a bobcat 611 that has an intermittent hydraulic problem.

 

 

one minute all three services (up/down, crowd and 3rd service) all work fine. the next minute all three services are very juddery, pump starts to screech and then all three services begin to fail.

 

problem seems to occur after 15 to 30 minutes of work

 

if i then leave the machine overnight everything back to normal for 30 minutes or so then problem again.

 

am using jcb universal oil (10w 30). oil is filled to correct level.

 

does anyone one have any suggestions.

[treequip]

Sounds like the pump is cavitating, this happens when it can’t get enough oil.

 

First place to look is the feed to the pump, is there a filter between the tank and the pump? Is the delivery hose between the tank and the pump in good order?

 

My first suspicion would be a filter in need of changing (there may be a filter in the tank as well) or the delivery hose is softening up as the oil warms up and is collapsing blocking the flow of oil.

 

Andy

[Justme]

Could be the pump on its way out. Very similar to the symptoms by tractor had when its pump needed changing. But check the filters & oil levels/condition first as I have had that as well.

[firewood]

Sounds like the pump is cavitating, this happens when it can’t get enough oil.

 

First place to look is the feed to the pump, is there a filter between the tank and the pump? Is the delivery hose between the tank and the pump in good order?

 

My first suspicion would be a filter in need of changing (there may be a filter in the tank as well) or the delivery hose is softening up as the oil warms up and is collapsing blocking the flow of oil.

 

there is a filter of unknown vintage, new one on order. will check the pipe and see if it is soft once warmed up

 

Andy

 

Could be the pump on its way out. Very similar to the symptoms by tractor had when its pump needed changing. But check the filters & oil levels/condition first as I have had that as well.

 

oil does look a wee bit cloudy so may be condensation (water in oil).

 

 

so i will change the oil, change the filter and check the pipe.

 

If it is the pump then the machine is off to the great scrapyard in the sky

[treequip]

oil does look a wee bit cloudy so may be condensation (water in oil).

 

 

so i will change the oil, change the filter and check the pipe.

 

If it is the pump then the machine is off to the great scrapyard in the sky

 

IF’ity IF. Did it start doing this when the weather got cold?

 

If there is moisture in the oil (it gets there out of the air) then ice could be blocking any filter, It’s a bit of an if but worth considering.

 

Andy

[treequip]

Could be the pump on its way out. Very similar to the symptoms by tractor had when its pump needed changing. But check the filters & oil levels/condition first as I have had that as well.

 

Could be but a knackered pump but I think oil starvation is more likely.

When the oil is cold and viscous they do OK but when it warms up the play in the pump means it can’t compress the thinner oil.

 

Knackered pumps don’t usually screech unless they are terminally wrong and then they simply don’t work at all.

 

Andy

[treequip]

If it is the pump then the machine is off to the great scrapyard in the sky

 

Ooooer,

 

That sounds a bit drastic

 

Before you bin it give these folks a call, they are in your neck of the woods (and by that I mean north of Shap) and good people to deal with

white house products uk - bobcat

 

If you do want rid of it I will be up as soon as the snow clears:thumbup1:

 

Andy

[firewood]

UPDATE

 

changed the oil today and ckecked inlet pipe. pipe sound.

 

fired her up and still juddering for around 5 minutes, pump screeching. then screeching stopped and no movement with any service. thought pump was kaput.

 

decided to unscrew flow from 3rd service to ram and dabbed pedal. oil sent shooting out after some bubbles escaped. reconnected pipe. still juddery bet getting better the more i used it.

 

I am now convinced the problem is ice crystals in the filter (was very cold this morning , -19 C)

 

 

will attempt to remove and replace filter when new one turns up tomorrow. I suspect it is still the original 1981 filter that came with the machine when new so its only done around 10,000 hours:lol:

[Breezeblock]

check the breather also as most hydraulic excavators usually pressurise the hyd tank to stop cavitation and have a look at the intake hose get somebody to operate it and check its not sucking itself flat or check that theyre are no flaps of rubber coming of the suction hose is it a gear type pump on these with an open centre valveblock and also are they hydrostatic drive its a few years since i have worked on these ps is it a skid steer or an excavator:thumbup:

[Treefitter]

I'm not dead certain but are you using the right grade of oil? You could try looking it up at

 

http://ew5.earlweb.com/search.php?site=6