Change Hydraulic Oil

PointyHairedBoss · Dec 22, 2010

I'm about to change the hydraulic oil in my new-to-me 2004 Kubota B21TLB for the first time (this is my first tractor). I don't know the condition of the existing fluid so I decided to start fresh as part of the machine's makeover. I have the 2 filters & oil - ready to go.
My question is about draining. Old oil will remain in the cylinders when I drain the system.

Is this anything to worry about?
Should I crack some of the hose connections to allow the oil to drain back to the sump?
Is there a position I should put the cylinders to assist draining (extended or retracted)?

I didn't see any details in the service manual regarding this.

IslandTractor · Dec 22, 2010

Most folks just ignore the relatively small amounts of oil that are in lines and cylinders. I've never done the calculation but it is probably less than five or ten percent of your total. If the current hydraulic fluid is cloudy or discolored I suppose it might be worth draining that peripheral fluid but if you are just doing a routine change then don't bother.

TripleR · Dec 22, 2010

There have been some other threads regarding this and the best I remember the majority opinion was consistent with IslandTractor's post.

gwdixon · Dec 22, 2010

The OCD folks raise the FEL to the top, drain the oil, then lower the FEL to squirt out the rest of the oil (engine off!). Same can be done with the bucket.

If it were me and I was worried about the old oil I'd just change it out again in 50 hours. No need to do the filters again. Then go to the recommendations in the manual.