Hydraulic Oil Level

[Jibber]

Ever since I took delivery of my new Kubota 3130 this spring, my regular checks of Hydraulic oil level have been high. My brother, who sells truck bodies and heavy equipment and works with hydraulics quite a bit pointed out that I liked to shut down the tractor then let the loader bucket down by releasing the valve.. he said that was probably introducing AIR into the hydro system and hence the higher levels on the dipstick. He advised me that construction workers have always told him to Power the bucket down.. shut off the tractor.. then relieve static pressure on the valve by rotating the stick.

OK. Well, last week I accepted deliver of a Backhoe, the BH-90 which taps into Tractor hydraulics (not PTO). Anyway. My levels now vary widely. Brother Jack advises me that before I was taking my levels while the loader bucket was on the ground, but with a backhoe, it's almost certain that at least one of the pistons is going to be extended at any time during an oil check. Typically the dipperstick cylinder and possibly the bucket cylinder because I tuck both up close to the tractor before shutting down.

OK.. end of dissertation.

My question. How do you guys take your hydraulic readings? Do you try to close up all the cylinders on loader/Backhoe or whatever? In the Kubota books.. I see no reference to what position implements (even the 3pt) should be in when taking Hydraulic levels.. yet it has a pronounced effect on those readings.

also.. what about powering down hydraulics versus just relieving the pressure and letting the weight bring the bucket down to the ground. Is that putting air in the system.. and what kind of problems could that create?

Thanks ahead of time.. I don't know what I would do without these forums.. Dealers have been giving me conflicting answers..

[Soundguy]

This may not be much 'current' info and help for you.. but my dipstick on my old ford reads 'check oil level with all cylinders extended'.. otherwise if you check it with all retracted.. you could run into an oil shortage when they are extended. Use your best guess.. because at some point, you may have enough aux circuits that your hyd sump may not be able to hold all the oil for all the cylinders to be extended... so go for a compromise level.. besides.. you won't really be using the fel or remotes much with the backhoe is working ..right?

Soundguy

[Jibber]

Good Point.

I'm surprised that there was no reference to it in my operators manuals.. maybe Kubota thinks that's something that should be explained by the dealer.. but neither the dealer I bought the tractor off of, or the other dealer that I bought the backhoe off of.. seemed to have the right answer.

It makes sense that you should have enough oil when you are performing the operation that involves the most extension of cylinders at any ONE time.. and you're right.. since you use the backhoe independently of the loader.. that would mean either or.. not both. The backhoe seems to have more hydraulics involved.. boom, dipperstick and bucket could all be extended during a deep dig.. I'll give it a shot extending the boom to ground level with the dipperstick and buckets tucked.. that should extend all cylinders.. and see what my oil level is then..

[Rch]

With a push/pull 2-way hydraulic cylinder its pretty much the same amount of oil in it whether it's extended or retracted. I can see collapsing a cylinder with gravity would add fluid to the reserse since there is no power to fill the other side of the cylinder. I understand there is plenty of extra fluid in a trasmission/hydraulic reserve when is at the top of its mark. Overfilling tends to froth-up and heat-up the hydraulic fluid. BTW, the NH mechanic says hydraulic fluid is too hot only when the paint on the tranmissiom/ reserve is burned [img]/forums/images/graemlins/shocked.gif[/img]

[Glenn9643]

Rch,

I've also noticed that the hydraulic fluid is lower on the level indicator glass when the loader arms are extended, and with the bucket lowered it indicates completely full. The additional fluid in the reservoir has to come from somewhere! The cylinders hold fluid when extended, and purge the fluid as the cylinder is retracted.

[jinman]

</font><font color="blue" class="small">( The cylinders hold fluid when extended, and purge the fluid as the cylinder is retracted. )</font>

I think you are correct, Glenn. The difference is the volume of the hydraulic rod/ram. It takes less fluid to retract the cylinder because the rod takes up probably 1/2 the volume of the cylinder. When you extend the rod, you use more fluid. I believe that's why the manufacturers suggest taking the fluid measurements with all cylinders extended. At most though, I would expect it to be not much more than a quart on a CUT with a backhoe and loader, because of the small size of the hydraulic cylinders. On larger construction equipment, it's much more, but they also have bigger reservoirs, so the overall effect is probably pretty much the same percentage. [img]/forums/images/graemlins/cool.gif[/img]

[Glenn9643]

With cylinders extended on my tractor the fluid level in the inspection glass is about halfway up, or to the center, which is OK. With cylinders retracted the glass is completely filled, which indicates that it is overfilled. The fluid has to be somewhere, and the cylinders are the only answer.

[Rch]

Glenn &amp; Jim, I see your point about the cylinders holding more extended because the ram is not taking up space. There is even a decal on my Bolens that says to collapse the FEL to check hydraulic fliud. [img]/forums/images/graemlins/blush.gif[/img]

[Jibber]

Well, it rained all day today here in Putnam County, NY.. so I decided not to wallow in the mud and rather cut wood for the long cold winter. In other words.. I didn't get a chance to play with the tractor and try different manipulations of the loader/BH to see how it affects levels. I think it makes sense to check levels either extended or compressed.. or in a resting state. I'll try all three. The thing about a backhoe is.. in it's resting state.. at least one cylinder is extended full.. (dipperstick). The only way to extend all is to dig a 9 foot hole!

[Hambone]

On the construction equipment and Hyd systems on trucks that I deal with daily, you check with all cylinders retracted.
But, one point is that all the equipment I deal with, the implements are all permanent mounted. So, it is designed to run the same numbers of cylinders.