[TR] Hydraulic Jack Question

[Dave1massey at cs.com]

In a message dated 3/7/2008 8:09:38 AM Central Standard Time, 
75TR6 at tr6.danielsonfamily.org writes: 
> What causes a jack or even an engine crane to stop holding a position and
> settle back down after a while? Is it low fluid or a bad gasket or a
> combination of things? I know that there's an industry standard for how much
> one can drop over an x period of time. But I'm talking about a matter of
> minutes with or without a load on it?
> 
The fact that some don't (most don't) is the amazing part.  The only thing 
that is keeping them in position is the fact that the oil is not leaking past 
the piston.  If yours is leaking it could be getting past the seal on the 
piston.  The oil is not lost, it is just going to the non-pressurized side of the 
piston.

Another possibility is that the valve is leaking.  That has the same effect.

Being low on fluid would not cause a long term drift.  It would cause the 
crane or jack to become "springy."  That is because air is compressible.  Oil is 
not (or relatively not).  Since you are not reporting this symptom it is 
likely not the problem.

Dave