Oil Recirculation in closed loop system

[marrt]

Whenever I repair a steering cylinder, I never fill it with oil before returning the cylinder to service. Yet, after a few cycles, everything works fine. Proving (I guess) the model JJ suggested.

However, let's consider a wheel motor. I once asked Terry has critical it was to get a new motor absolutely full of oil before mounting back on the tractor. He said it wasn't critical at all. In fact, I didn't even have to fill it AT ALL for everything to work (he didn't recommend dry-starting a wheel motor...he was just talking "technically" about the plumbing). The motor would fill up and run fine.

We've had numerous conversations on here over the years about how the wheel motor circuit is closed loop and, other than a little make up oil for bypass, never really gets filtered etc.... If so, how does the system flush air out of the loop in a scenario like Terry suggested?

 

[woodlandfarms]

I think the pumps are the only thing you need to get the air out of, due to the fact that they spin to pressurize so if there is air there is no lubrication....

 

[J_J]

The closed loop hyd system is not really a closed loop.

The charge pump is there to make up any fluid lost to leakage, and provide fresh cool fluid to the pump casing, and doing so, the air is purged for the most part.

It pumps about 10% of the VSP pump, so it is always pumping. That is the only fluid that is being filtered.

There is however a bleeder valve on some of the pumps to purge the air faster.

Any air in the system will normally flush out, but there could be a spot where an air bubble night reside and cause some problems.

Although some pumps will prime themselves, it should be done at slow speed, such as cranking but not starting.

I recommend filling a pump, filters, anything you can get to.

My wheel motors have case drains, so I know they are getting fresh fluid at some time.

 

[SpringHollow]

When I have to replace my hoses etc, I thought about putting in some Tee's for flushing with an external pump to purge but the cranking might work just as well. I do that like you are supposed to when changing filters but it never occurred to me do it for general air purging on wheel circuits etc. Thanks for the idea.

Ken