hydro help??

[fiveoford89]

I have a mid 80's case backhoe. As I operate the backhoe portion of this machine I sometimes lose Hydraulic pressure while the lever is in the nuetral position which causes the boom fall. When it does this it happens slowly. When I operate the proper lever, pressure will return and I can pick up the boom without a problem. This happens only with the main boom( i believe its refferred to as the shoulder) When I use the front loader I have no issues and it works perfectly. Does anyone have any ideas what can cause this? I have checked my fluid levels and they appear to be fine. Any help or ideas would be greatly apprieciated:thumbsup:

 

[AKKAMAAN]

I sometimes lose Hydraulic pressure while the lever is in the nuetral position which causes the boom fall. When it does this it happens slowly.

So when you first say it is falling (the main boom), and the you say it goes slowly, which is more like a drift....so we need to decide which case it is, "FALL" or "DRIFT"....approx time??

We also need to know what auxiliary valves are connect to the main boom circuit...between the control valve and the cylinder....if this "fall or drift" happens occasionally, there might be a work port valve in the control valve that is "playing" with you, or a possible auxilary pilot operated check valve doing the same thing....

Try to post some detailed pics from the control valve and any aux valves involved...

 

[fiveoford89]

Ok- will do- thank you

 

[kennyd]

It sounds like the "load check" in the valve is going bad...It's purpose is to keep the cylinder from moving until there is positive hydrauilc pressure applied.

 

[J_J]

Switch the boom cyl hose to another spool and see if the boom still falls. If it doesn't, then the cyl is bypassing.

 

[J_J]

I believe valve load checks only come into play when the levers are moved to keep the load from shifting. When the levers are in neutral, the spools close off the ports. If any leakage occurs at the valve, it is probably because of wear and tear on the valve spool, or spool not fully in neutral.

It also prevents the back-flow of oil from the work port to the inlet. The pump must build up enough pressure to overcome the pressure on the
work port caused by the weight of the load
before the cylinder can move.

I have the D-100 Case backhoe on my trencher, and it will stay up for days.

 

[AKKAMAAN]

I believe valve load checks only come into play when the levers are moved

+1 agree

 

[TraderMark]

It could be a port relief depending on the size and actual model of the backhoe.

Is it a 580? Mid 80's could be a 580C or 580D...

Some of those used port reliefs and others used plugs that just filled the port relief holes, but the orings around the plugs could allow leakage.

Give us some more info please.

Mark

 

[fiveoford89]

it is a 580D- where would i look to see if if I have the plugs or the valve?

 

[TraderMark]

Go here: CASE

You can then click on the "Launch Parts Catalog" link and look up your machine to view a complete parts catalog online.

Looking at the attached picture, items 11-15 are your port reliefs, one in each side of the valve.

Mark