Cylinder Leak Down test?

[Bedlam]

Hello, I am attempting to probably rebuild the lift and curl cylinders on my Ford 7108 Loader. After viewing a few U Tube vids I had never thought that the leak down (thats slowly gotten worse over the years) could be the control valve . So I found this video of how this woman checks for it.

Anyways I just checked mine this way.

Raised the arms up and supported them. Then removed the quick disconnects. (for the lift cylinders). And then removed the support. It lowered pretty quickly. So I assume it has to be the seals in the cylinders ,as the control is no longer connected to it.

Is this how its normally done?

 

[kennyd]

Yes, that's how it's done. It usually is the seals vs the valve.


Here is another way to do it, but it's really overkill.

 

[LD1]

If you are talking about the curl cylinders.....yes.

If you are talking about the lift cylinders.....the main boom will not leak down if the disconnects are unhooked. Oil has to go somewhere. So you either have alot of air in the cylinder or it's leaking oil on the ground

 

[Bedlam]

If you are talking about the curl cylinders.....yes.

If you are talking about the lift cylinders.....the main boom will not leak down if the disconnects are unhooked. Oil has to go somewhere. So you either have alot of air in the cylinder or it's leaking oil on the ground

Thanks. yes i checked the lift cylinders but will try the curls next. (disconnecting them) Luckily there are no leaks on the ground..

 

[LD1]

Well you got something else going on as I mentioned.

You can completely remove the piston seals in the lift cylinders and it shouldn't drop a bit with the control valve isolated.

You either have air in the cylinders, leaking oil on the ground you aren't seeing, or you unhooked the wrong disconnects

 

[Fallon]

Well you got something else going on as I mentioned.

You can completely remove the piston seals in the lift cylinders and it shouldn't drop a bit with the control valve isolated.

You either have air in the cylinders, leaking oil on the ground you aren't seeing, or you unhooked the wrong disconnects

Yup. Also why crossover relief valves don't work on double acting cylinders.

If you don't see oil coming out, it's either air or a leaky valve.

 

[Bedlam]

''

You can completely remove the piston seals in the lift cylinders and it shouldn't drop a bit with the control valve isolated.'' this part has me stumped.without the seals how can this be? I disconnected the two correct hoses . this eliminated the valve all together. So if the seals in both cylinders were ''good'' then how could oil get past. Even with both cylinders connected together the pressure would be on both cylinder seals. If one or both were worn (30 years old) then the oil would leak past and be in the 'upper' part of the cylinder. Not sure what I am missing here.

 

[Tx Jim]

As rod on boom cylinder travels into cyl barrel the rod will occupy a portion of volume(space) that was occupied by oil that was in butt end of piston barrel. If rod enters cyl barrel then that butt end oil must go somewhere to allow space for rod. Rod can't enter barrel any further due to no available space for cyl rod(shaft) due to presence of oil

 

[rScotty]

''
Not sure what I am missing here.

As Jim says, what you are missing is that when the cylinder is retracting, in order for the rod to have room to enter the cylinder that same amount of oil has to go somewhere else. That much oil has to completely leave the cylinder.

 

[ROUSTABOUT]

If you are talking about the curl cylinders.....yes.

If you are talking about the lift cylinders.....the main boom will not leak down if the disconnects are unhooked. Oil has to go somewhere. So you either have alot of air in the cylinder or it's leaking oil on the ground

Piston can bypass internally...